Getting Started

1. Upload a photo of your object. Include a ruler, framing square, or printed reference sheet for scale.
2. Correct perspective — choose a method: 4 Corners, Lines , Circle, or Ref Sheet.
3. Set scale — enter real-world dimensions, or let Lines / Circle / Ref Sheet set it automatically.
4. Trace — draw over your corrected image with the Draw tools, or let Smart Trace in the Detect panel do it for you.
5. Download a true 1:1 DXF. Trace two or three sides of the same part and the 3D button beside Download builds a solid model from them.
6. Verify accuracy with the Measure tools before exporting.

Photo technique (the most important factor):

• Shoot from mid-height on your subject — not standing and looking down. Downward angles cause the worst perspective distortion.
• Use your phone's telephoto lens for large objects — less distortion than wide-angle.
• Avoid the ultrawide lens — barrel distortion near edges is severe.
• Transfer photos via AirDrop or cable, not screenshots. Screenshots strip EXIF lens data.
• Include a framing square or ruler in the frame for scale — it doesn't need to touch the object.

Put CAD on your phone

CAD works best as an app on your phone's Home Screen: it opens full screen, with more room to draw, and it is one tap away when you are standing at the part.

• iPhone or iPad: in Safari, tap Share (the square with an arrow), scroll down, tap Add to Home Screen, then Add.
• Android: in Chrome, tap the ⋮ menu at the top right, then Add to Home screen (or Install app).

Show me how

Photo Technique

The quality of your photo is the single biggest factor in measurement accuracy. Good technique beats any software correction.

Camera height and angle

• Crouch to mid-height of your subject for side profiles. Standing and pointing down causes severe top-to-bottom foreshortening that's hard to correct fully.
• For top-down views (ref sheet, flat parts), get directly overhead — a small step stool helps.
• Being 10–20° off perpendicular is fine — CAD will correct it. Being 45°+ off is where accuracy degrades significantly.

Which lens to use

• Use telephoto (2× or 3× zoom) for large objects — longer focal lengths compress perspective distortion.
• Avoid ultrawide — the barrel distortion near the edges is severe and can't be fully corrected without a calibrated lens profile.
• Standard (1×) lens is fine for most work. iPhones auto-correct barrel distortion in JPEGs automatically.

Lighting

• Even, diffuse lighting is best. Overcast days outdoors or indirect indoor light works well.
• Avoid harsh shadows across your subject — they obscure edges and confuse auto-detection.
• Avoid direct sunlight on metal or glossy surfaces — specular reflections hide geometry.
• High contrast between the object and background dramatically improves AI and Hough detection.

File transfer

• AirDrop or USB cable — preserves full EXIF data including focal length and lens model.
• Screenshots — strip all lens metadata. CAD can't match a lens profile to a screenshot.
• iCloud Photos, Google Photos — generally safe if you download the original (not a compressed version).
• HEIC files are fully supported and slightly smaller than JPEGs. No need to convert.

Reference tools in the shot

• Always include a framing square, ruler, or reference sheet in the same plane as your subject.
• The reference doesn't need to touch the object — just be visible in the frame and on the same surface.
• For wall-mounted objects, hold a framing square against the wall beside the object.
• For objects on a floor, lay the framing square flat on the same floor surface.

Large and organic shapes

• Objects too large for the Ref Sheet (chairs, cabinets, doors): use a framing square + Lines Corner mode.
• Organic shapes with no straight edges (curved furniture, freeform parts): the framing square provides the reference geometry — the object itself doesn't need any straight lines.
• Multi-face objects: capture each face as a separate view with + View. Each gets its own correction.
• Parallax is the real limit — if the camera angle causes near parts to block far parts, no software can recover that hidden geometry.

Perspective Correction

4 Corners — Click the 4 corners of any rectangle in the image (table edge, door frame, floor tile, piece of paper). Most accurate method. Best whenever a rectangle is visible in the scene.

Lines — Corner mode — For a framing square or any L-shaped reference. Click the corner point (where arms meet), then each arm end — 3 clicks total. Enter arm lengths for automatic scale. This synthesizes a full 4-corner correction from just 3 points, giving far better results than floating lines. Best field method for organic shapes with no rectangular edges.

Lines — — Float mode — Click 2 endpoints on one straight edge, then 2 on a perpendicular edge. Use when the edges don't share a corner. Less accurate than Corner mode — only corrects tilt, not full perspective.

Circle — Click 5+ points around the rim of something round (coin, washer, hole, wheel). The photo is stretched until that rim is round again, and with Tight crop it is cut to a square around it. If the rim is already round in the photo, nothing is stretched and the status line says so. Enter the known diameter for automatic scale, or leave it empty and set the scale on the next step.

Ref Sheet — Print a reference sheet, place your object on it, photo from above. Automatic perspective + scale in one step. Most accurate for small to medium parts.

Field workflow for large or organic objects (chairs, furniture, curved parts):

• Place a framing square on the same surface plane as the object — it doesn't need to touch it, just be in frame.
• Use Lines Corner mode with the square's corner and arm ends.
• Crouch to mid-height of the object before shooting — this is more important than being perfectly perpendicular.
• For objects with multiple faces (chair front, side, top), capture each as a separate view using + View.
• What perspective correction can't fix: parallax (near legs blocking far legs), lens distortion (use a calibrated lens profile), and physical rotation of the subject.

Reference Sheet

Print a reference sheet from the Ref Sheets & Tools page. Available in 4 sizes:

• Small (a 4×6" card, printed on Letter paper) — small parts, up to about 2.5×4.5". The camera can come close to it, so the part is traced at almost twice the detail it gets on a Letter sheet. Cut the card out, or leave it on the page.
• Letter (8.5×11") — hand-sized parts, desktop objects
• Tabloid (11×17") — medium parts, sheet metal
• Large (24×36") — panels, assemblies, floor plans

Each size also available inverted (white on black) for better contrast with light-colored objects. CAD auto-detects which sheet you're using.

1. Print at 100% scale (no fit-to-page).
2. Place your object on the sheet.
3. Photo from above — all 4 markers must be visible.
4. Select Ref Sheet mode → Detect Sheet → Apply.

Object thickness: Enter thickness for non-flat objects to correct parallax. Enter 0 for flat items.

Markers not detected? Glare, a fold or a marker partly under the part can stop the automatic detection even when you can see all four. Tap Place corners by hand, drag the four handles onto the middles of the four markers (top-left, top-right, bottom-right, bottom-left), say which sheet you printed, and press Use these corners. The correction and scale are exactly what detection would have given; naming the wrong sheet gives the wrong scale, so check that one.

Scale Calibration

Ruler — Click two points along a ruler and enter the distance. Default after 4 Corners.

Edge Dims — Enter width and height of the rectangle from 4 Corners.

Dual Rulers — Two perpendicular rulers for independent X/Y scale. Most accurate method.

Scale is automatic with Lines (with lengths), Circle (with diameter), or Ref Sheet.

Lens Profiles

Lens profiles correct barrel/pincushion distortion from your camera lens, improving measurement accuracy — especially near the edges of photos.

How it works: Profiles are saved in your browser automatically after calibration. When you select "Use Saved Profile" and process a photo, CAD matches the profile to your camera using EXIF data (device model, lens, focal length). You don't pick which profile — it's automatic.

Multiple cameras: Modern phones have several cameras (wide, ultrawide, telephoto). Each needs its own profile — calibrate each one separately. CAD distinguishes them automatically by focal length. All your profiles are listed on the upload screen.

Backup your profiles: Browser storage can be cleared by OS updates, clearing browsing data, or switching browsers/devices. Use the button next to each profile to download a .lenscal backup file. You can re-import it anytime with the + Import button on the upload screen.

Renaming: Use the button next to any profile to give it a friendly name (e.g. "iPhone 15 Pro Wide" or "Shop Camera").

To calibrate: Go to Camera Calibration, print the Charuco board, take 10+ photos from different angles, and upload them. The profile saves automatically.

Do I need a profile? Most modern iPhones apply lens correction to JPEGs automatically — profiles may have minimal effect on standard photos. Profiles matter most for ProRAW images, older devices, or cameras that don't auto-correct. If your measurements are already accurate without a profile, you don't need one.

Draw Tools

Click Draw in the bottom bar to open the draw panel. The panel is organized into sections: Create, Modify, Arrange, Clean up, Selection, and Clipboard & history.

Bottom toolbar: When the draw panel is open, the bottom toolbar shows context-sensitive controls — Snap toggle and sensitivity, Ortho, and Guides, plus Brush size and Tolerance only while the tool you picked uses them. Tolerance is how far a tap on Sm Polyline, Straighten, Fit Arc or Circle looks for an edge in the photo to land on (it needs Detect Edges or Smart Trace run on the view first), and how hard Smooth smooths. On mobile, dimensional inputs (W×H, R/D, L, and the Polygon's Sides) also appear here when a draw tool is active. Colours and line weights are set per layer, from the swatch on each row of the Layers panel.

Create:

• Polyline — Click to place points. Double-click or Enter to finish. The result is ONE polyline, so its corners always stay joined. With three or more points down, snap to the start point to close the shape (green ring). Finish on the free end of another line or curve on the same layer and it offers to join the two into one outline. Undo (or Backspace) takes back the last point.
• Curve — Click control points, double-click or Enter to finish. Smooth Catmull-Rom spline.
• Circle — Cycles: Center / 2-Point / 3-Point. Type R or D for precise sizing.
• Ellipse — Click 2 points for major axis, 3rd click sets width.
• Rectangle — Cycles: Corner (2-click) or W×H (type dimensions, click to place). All 4 lines auto-grouped.
• Polygon — A shape with equal sides. Type how many sides in the bar (3 to 100; 6 to start). Press the button again to switch how you place it: Corner — click the centre, then where a corner goes (the corners sit on a circle); Flat — click the centre, then the middle of a side (the circle touches every side, the way a nut is measured across its flats); 2-Pt — click the two ends of one side. The preview shows the shape and, in Corner and Flat, its circle. Ortho keeps the second click level or plumb with the first, so a side lies flat. For an exact size, type it in the bar before you click: in Corner and Flat it is the size across the shape (⌀) or from the centre (R, press ⌀ to switch), and one click places it, centred there and sitting on a flat side; in 2-Pt it is the length of one side. In 2-Pt the shape is built on the left as you go from the first click to the second: click the two ends the other way round to put it on the other side. It is one closed shape, so Fillet, Offset and Explode work on it like any outline.

Modify:

• Move — Select geometry, then tap a point on it (it snaps to corners, ends and centres) and tap where that point should go; it snaps there too, and Ortho keeps the move level or plumb. Or skip the taps and type dX and dY in the bar, either or both (+ moves right and up; the units are the part's, or pixels with no scale), then press Enter or ✓.
• Rotate — Select geometry, then: (1) click the pivot point, (2) click a reference point (defines the "from" direction), (3) drag to rotate — release to confirm. The Snap / Free button on the Rotate bar: Snap (the default) turns in 22.5° steps, Free to any angle. Shift — the snap key — flips it while you hold it, and on a touch screen a second finger can tap the button while the first is still turning (Ctrl still frees the angle too). Snap on = pivot/reference/endpoint snap. Snapping to a geometry point overrides the 22.5° interval. Type angle in the bar for precise input: a positive angle turns counter-clockwise, a negative one clockwise, as in CAD.
• Scale — Select geometry, click anchor, click handle, move to scale. Toggle proportional/1-axis.
• Mirror / Symmetry — One button, two tools; press it again to switch. Mirror: select geometry, click two points to define the mirror line, and it makes reflected copies. Symmetry: draw the line of symmetry, then tap the half to replace (each half is labelled) and it is rebuilt as the mirror of the other — the quick way to make a traced outline truly symmetrical. Undo restores.
• Array / Circular array — One button, two tools; press it again to switch (the bar's Grid / Circular button switches too). Select the shapes first; both count them as the first item, so 4 columns makes three copies. Array: type Cols and Rows, and dX and dY, how far from one copy to the next (+ is right and up; the part's units, or pixels with no scale). It starts with the copies just clear of each other. Or tap a point on the shapes and then where that point lands in the next copy (one column over, or diagonally one column and one row for a grid): it snaps to corners, ends and centres, and sets the spacing. Circular array: tap the centre (it snaps, so a bolt circle's centre is one tap), then type Count and the Angle to fill: 360 spaces them evenly round a full circle; a smaller angle puts the first and last copies at its two ends (+ is counter-clockwise). Turn spins each copy with the circle, like spokes; Upright keeps each the way it was and only moves it round. The preview shows the copies; ✓ or Enter makes them, all in one Undo, on the same layer, and leaves the whole array selected. A copy that would land exactly on a shape already drawn (a ring of tabs that is the same all the way round, say) is left out, and the status line says how many.
• Offset — Select geometry and the offset previews outward at the last distance used. Type a distance, Flip to go the other way, and confirm with ✓. Tapping a side of the shape sets the side by hand. A traced outline or a group of lines and fillets comes back as one outline exactly the distance away at every point, even where a trace steps in small jogs: corners stay sharp, fillets stay true arcs, and anything the offset would fold back through is trimmed off. An offset wider than the shape says so instead of drawing nothing. What Offset draws is drawn round the part, so Part only never shows the photo inside it.
• Fillet — Click a corner where two lines meet to add a radius fillet. The fillet arc automatically joins the group of the corner lines. It also works on a traced outline, where the corner is a vertex inside one polyline rather than a junction of two lines; a radius that would eat more than half of either side is refused with a reason rather than folding the shape.
• Divide — Click a line or curve to select it (highlights cyan), then type how many equal segments to divide it into. A live preview shows where the division points will land. Press ✓ or Enter to confirm. The resulting segments share a new group. Works on lines, spline curves, and fillet arcs.
• Convert — Switch a point on a polyline or curve between a sharp corner and a smooth curve. Corners show as orange squares, smooth points as green circles; tap one to switch it. Making a point of a plain polyline smooth turns the shape into a curve through the same points, so making them all smooth gives the curve you would have drawn; making every point of a curve a corner turns it back into the straight polyline. On a polyline that already has arcs, a smooth point becomes two arcs meeting smoothly. Points never move. End points of an open shape cannot be converted. Undo puts it back.

Arrange:

• Align L / Align T — Align selected items horizontally (left/center/right) or vertically (top/middle/bottom) to a clicked reference point. Click button to cycle modes.
• Dist H / Dist V — Distribute selected items so the gaps between their edges are equal. Keeps the outermost items in place, spaces the intermediate ones. Respects groups. Needs 3+ independent items.
• Group / Ungroup — Group items so they move/align as one unit. Brush-selecting a group member selects the whole group.
• Join / Explode — Join turns selected lines, arcs and polylines that meet end to end into one polyline (handy for drawings made before polylines were saved as one shape). Curves joined only to curves stay one curve, with the same points they were drawn with, each joint a corner (Convert smooths one). Joined to lines, a curve's straight stretches stay single lines and only its bends are kept point by point. Explode breaks a selected polyline back into separate lines and arcs; rounded corners stay true arcs.

Clean up:

• Clean Up — Tidies traced geometry: thins out crowded points, gives parts that share an edge one averaged edge, and drops any shape the others already describe. Undo restores everything.
• Smooth — Paint over geometry to smooth it, in two stages. On a curve carrying a lot of points the first tap simplifies it: the points that carry no shape are removed and the ones that do are kept, which is what makes a ragged outline read smooth. Tap again and it averages the remaining points, which only bites once they are far enough apart to disagree. Sharp corners (90° and 45°) and traced fillets are held through both. With points collected in Edit Points it fits an arc through them instead, the same as Fit Arc.
• Fit Arc — For a curve that came back faceted. In Edit Points, paint across that stretch, then press Fit Arc — or Smooth, which does the same while points are collected. Pressing Fit Arc with nothing painted puts you straight into paint mode and fits as soon as you lift. It works on anything drawn: a traced outline, a chain of lines and fillet arcs, or two outlines joined end to end. It fits a true arc (or a smooth curve, if the points are not on one circle) and replaces just that stretch, leaving its ends exactly where they were so the neighbours stay joined. The result exports as a real arc, not a fan of straight segments, and has one handle at its middle. It refuses, and says why, for a single straight line, something that is already a true arc, pieces that do not touch, or a whole closed outline.
• Snap Corners — Extends nearby line endpoints to meet at clean corners.
• Weld Ends — Merges endpoints that look touching on screen but are not quite joined, and closes an outline whose own two ends meet. Its reach follows the zoom: zoom out to weld a wider gap, zoom in to keep close ends apart.
• Standardize — Opens a popup with three options: Circles (groups similar diameters and snaps them to round sizes — the diameter, not the radius), Rectangles (resizes from center), Fillets (rebuilds each at the standardized radius). Tap the same button again to round coarser: 1/16" → 1/8" → 1/4" → 1/2" (0.5 → 1 → 2 → 5 mm). The popup stays open and its status line reports each pass; Undo restores.

Selection:

• Select — Click to select/deselect (yellow = selected). Drag to paint-select multiple items — brushing any part of a group selects the entire group. Drag selected geometry to move it. Copy/Paste with Ctrl+C/V. Tap Select again to deselect everything.
• Edit Points — Drag a handle to move that point, tap the outline between handles to add one, press and hold a handle to delete it (mouse or finger). Drag across empty space to paint-collect several points, then drag any of them to move them all, or press Delete Sel to remove them and join the neighbours across the gap. Tap Edit Pts again for Multi mode, where a paint stroke can start on a handle too; an amber dot on the button shows it, and tapping again goes back. Every point is a handle at every zoom, and every point can be snapped to. Dragging between handles never moves the whole shape here — that is Select’s job. A rounded corner is a true arc with one handle at its middle: drag it to make the arc deeper or flatter. Move a point beside a fillet and the fillet is rebuilt to stay tangent. Drag the free end of a line onto another piece’s end and it offers to join them.
• Erase — Click geometry to erase or trim at intersections. Brush over multiple items to erase them.
• Deselect All / Delete Sel / Clear All — Clear the selection, delete what is selected (or the collected points), or clear everything drawn. All undoable.

Clipboard & history (folded until you open it): Copy, Paste, Undo and Redo. The same four are on the grab bar and the keyboard (Ctrl+C / V / Z / Y).

Detection: lives in the Detect panel — see the Detect & Smart Trace section below for the four modes, the Guide Brush, and accepting results.

Snap: Points snap to every point of existing geometry, plus centres (a traced round hole counts), quadrants, midpoints, corners, and where a fillet meets a straight side. They also land on a line or curve anywhere along it (ON), where two shapes cross (INT), and, from the last point you placed, at the tangent of a curve (TAN) or square to a shape (PERP); a guide or Ortho line crossing a shape snaps to that crossing. Toggle in toolbar or panel. Hold Shift to momentarily flip it. With snap off, a finished line ends exactly where you ended it.

Ortho: Constrains drawing to horizontal/vertical. Hold Ctrl to momentarily toggle.

Guides: Off to start with: tick Guides in the bar to use them. Rest the cursor or your finger on a snap point (an end, a vertex, a centre, a midpoint, or a point you already placed in the shape you are drawing) for a moment and it becomes a tracking point, marked with a small green square; a ring fills while you rest. Rest on it again, after moving away, to remove it. Up to four at a time, kept until the shape or the drag is finished. Every tracking point, the last point you placed, and a dragged point's own starting position cast dashed level and plumb lines, and a tracked end of a straight line casts its extension; your point snaps onto a line it comes near, and onto the crossing of two lines first. From the last point placed you also get parallel and perpendicular lines (level 30 and up) and tangents to circles (70 and up). The level sets how far a line reaches. Works while drawing, in Mirror, and while dragging points, brushed points or a group, on a phone too. Point snap wins over a guide and Ortho wins over both. Hold Alt to momentarily toggle.

On a phone in portrait the grab bar at the top of every panel — and a row above the canvas when no panel is open — keeps the everyday tools in reach: Copy (it turns into Paste once something is copied, and tapping it again goes back to Copy), Smooth, Select, Edit Pts, Erase, Undo, Redo and Delete.

Switching tools with work waiting: if a polyline, curve or other tool is waiting for its ✓ and you pick another tool, it asks before throwing that work away.

Download writes everything you have drawn, on every view, into the DXF — there is nothing to apply first.

Curves: the Curves select in the Download dialog decides how a smooth curve is written. True splines (the default) writes each one as a single DXF SPLINE — exactly the curve on screen, in a dozen control points, and what CAM wants, because a spline gives one smooth toolpath where a many-sided polyline gives a tiny straight move per segment. Line segments writes the same curve as a dense polyline instead: the same shape to well under a thousandth of an inch, for CAD or CAM that reads splines badly. Circles, arcs and fillets are unaffected — they are always true arcs.

Detect & Smart Trace

Detect and Smart Trace are for photos. A drawing is converted into lines instead, so a drawing’s views have no Detect button.

Click Detect in the bottom bar. Pick a Mode first; the Guide Brush and the Auto box (re-run when a setting changes) sit just above Run, which runs whichever mode is picked. Each mode shows only its own settings. Below the results come the same Clean up and Selection groups as the Draw panel, and History (Undo, Redo).

• Auto Outline — AI segmentation finds the part's outer boundary plus interior edges. The green Boundary and orange Interior buttons toggle each result layer; Threshold, Passes, and Min size tune the two layers independently.
• Edge Scan — classic edge detection with Contrast / Threshold / Detail / Smoothing sliders. Results go to the blue edge layer, kept separate from the Auto Outline layers.
• Detect Inside — drills into a region for nested shapes. Select a closed outline with , or paint a guide region, then Run. Repeat on results to go deeper.
• Smart Trace — AI reads the photo and names each component; precision edge-snapping does the measuring. One run returns every interpretation: the Smooth / Organic / Auto / Polygonal shape buttons switch instantly, and the Styles panel adds Edge outline (traced from the part's own edges rather than from the AI, often the sharpest choice on a reference sheet) and can show several at once so you can mix — keep the outline from the style that traced it best, the interior from another, erase the rest. Switching styles is free; only the run is counted. Each run uses one of your Smart Trace runs (a re-run of the same view uses half, and a failed or cancelled run is given back). Before any AI run starts, a box says what it will use and how many runs you have, and nothing is spent until you press Run. Pro and Studio add runs every month; your account page shows what is left. An optional AI prompt scopes what gets traced. Cancel any time; a run that dies mid-flight retries itself once.

Guide Brush — paint over the area you care about, then Run: every mode detects only inside the painted region. The paint is kept after a run so you can re-run other modes on the same region, and the brush automatically picks a colour that stands out against your photo.

Accepting results: tap a suggestion to accept it, or Accept Visible for everything shown (the type filter buttons apply). Fit converts raw contours into line and curve suggestions. Clean Up (in the Clean up group, with Smooth, Fit Arc, Snap Corners, Weld Ends and Standardize) does three things in order: thins out points crowded together without changing the shape (traced fillets are protected), seams shared edges so adjacent parts butt together exactly, then drops any shape the others already describe — Undo restores everything.

Smart Trace's named components land on their own Layers (next section) and export as named DXF layers.

On a multi-view part each run knows the others. Every run records which side it traced and what that outline measured; the second and later runs are told what the earlier ones found, so the AI knows how big the part should be in this photo. If a view comes back the wrong size for the side you labelled it, Smart Trace says so under the status line and offers to relabel it — a wrong label builds the wrong 3D model, so it is worth a look before you go on.

Naming the project. A photo uploaded without a name is called by its file name (IMG_8322.jpeg). After a run, Smart Trace knows what the part is, so it offers its name for the project under the status line: Use this name, type Other name…, or No thanks. It only asks while the project has no real name, and only once; the name is what your saved project and downloads are called.

A second look, and symmetric parts. Before a run finishes, Smart Trace measures small features on a zoomed-in copy of the photo and looks over its own tracing once more: it adds a feature it missed and drops one it traced twice. It also says whether the part is symmetric. When it is, a Symmetric left / right (or top / bottom) button appears under the shape buttons. Tap it and one half of the tracing is mirrored onto the other, about the dashed line drawn on the photo, so the two sides match exactly — the way you would draw half a part and mirror it. The line is measured on the traced shapes, not guessed. It keeps the half the traced styles agree on best; Use right (or Use left) mirrors the other half instead, and tapping Symmetric again gives the tracing back as it came. A hole on the line is centred on it, a pair of holes is averaged, and a feature with nothing opposite it (a button on one side) is left as traced. Compare both halves before you accept: on a well-traced part the plain tracing can be the more accurate one.

Round parts and tidy circles. When the part itself is round — a pipe end, a cap, a disc — Smart Trace gives its outline as a true circle and fits it, and each ring inside it, to the edge all the way round, so a busy background such as gravel does not pull it off. When a run finds two or more circles, a Tidy round features button appears under the shape buttons: circles that nearly share a centre are made to share it (on the part's own outline when it is one of them), and holes of nearly the same size are made the same size. Tap it again to see the tracing as it came.

Layers

Click Layers in the bottom bar. Smart Trace names each component ("body", "trigger", …) and each name is a layer; hand-drawn geometry starts Unassigned.

• Visibility — a hidden layer disappears everywhere: canvas, loupe, snapping, and hit-testing, so invisible geometry can never be selected, snapped to, or erased by accident.
• Lock — a locked layer stays visible and snappable (that is what a reference layer is for) but cannot be selected, moved, edited, or erased.
• Reference view — the row at the bottom of the panel shows another view's geometry on this one, dashed in lavender, to line things up against. Views that share one axis (top and front share the width) are projected: a dashed line runs across this view at every corner and extreme of the other view's shapes, along the axis the two share, and snapping or a guide lands on it exactly. Views of opposite faces (top and bottom, front and back, left and right) are overlaid, mirrored to match, and their features snap and guide like your own geometry. It is lined up with this view's outline, or centred on the photo when nothing is drawn here yet: tap Move and drag on the canvas to slide it onto the part (along the axis it is projected on), then draw against it; Align lines it up with this view's outline again. A chain of lines and fillets on the other view is projected as one outline, so a rounded corner gives its tangent points rather than a line at every joint. It is never exported and cannot be edited or selected.
• Imported parts — the rows for parts brought in with File › Import part: its photo on or off, show or hide it in every view, Move, Turn, Rotate and remove. Move tapped once lets you drag it on the canvas (it snaps; every view follows); tapped again it moves point to point like the Draw panel’s Move: tap a point on the part, then where that point should go (it snaps to your drawing and to the other parts), or type the distance in the bar; a third tap puts it down. Turn is the quick one: a quarter turn clockwise as seen here. Rotate turns it by any angle, like the Draw panel’s Rotate: tap a pivot, tap a reference point and move to turn it (22.5° steps, or free with the bar’s Snap button — Shift, or a second finger on that button, flips it while you turn), or type the angle in the bar to turn it about its own centre. A view that sees a turned part at an angle shows its 3D body from there, wearing its photos as the 3D viewer does (a side no photo covers is tinted in its colour), with the outline dashed: it is worked out, not photographed. Align lines the parts up with this view’s drawing again, or centres them when nothing is drawn here. An imported part is never edited, but its outline can be used: in Select, tap it (or paint across it) to pick it as a reference — it is highlighted dashed. A part drawn in pieces (separate lines, or shapes that touch) is picked by its whole outline on the first tap on its edge; tap again for just the line under your finger, and a third time to drop it. Then Offset it (the offset outline is added to your own drawing, the quick way to draw a housing wall round it) or Copy it (it pastes in place as your own geometry, to edit). Moving, turning, lining up and removing a part can be undone with Undo; showing, hiding and its photo are display settings and are left as they are.
• Photo — the first row: show or hide the photo behind the drawing.
• Colour and line weight — tap a row's swatch (the coloured bar) to set that layer's colour and how heavy its lines are. Both are written onto the DXF layer (the weight as its lineweight, shown in mm), so the part opens in CAD the way it looks on screen. Unassigned geometry uses the Unassigned row's colour.
• Dimensions — the last rows. Every dimension is on its own layer, exported as DIMENSIONS; set its colour and line weight there, hide it, lock it (locked dimensions cannot be moved), or delete every dimension on the view. Texts, leaders and a drawing’s own text each have a row of the same kind once there is one on the view (Text, Leaders, Drawing text), exported as TEXT, LEADERS and DRAWING_TEXT.
• Rename — renaming a layer renames the component in your CAD export; renaming onto an existing layer merges into it.
• Solo — press and hold a row's eye or padlock to isolate that layer: everything else is hidden, or everything else is locked. Hold again to bring them all back.
• Active layer — the row with the blue bar is where new geometry lands. Tap a row with nothing selected to make it active; tap it with geometry selected to move that geometry onto it.
• 3D — the chip on each row is lit while that layer is part of the 3D model. Tap it to leave the layer out of the model (it still draws, and still goes into the DXF); 3D all at the top takes every layer out, or brings them all back. Hold the chip to make the layer an add-on body (it reads 3D+; see 3D Model). Changing this resets the per-shape extrudes in the 3D model, and the status line says so.
• Delete a layer and the shapes on it go with it, on every view of the part; the confirmation says how many on each. Undo restores all of it.
• Unassigned geometry exports to the AUTO_TRACE_FIT layer, as always.

A locked layer draws grey on the canvas, so what you can actually edit reads at a glance without opening the panel. That is display only: the swatch still shows the layer's real colour and the DXF still exports it.

Photo

Click Photo in the bottom bar for everything done to the photo itself, in this order: show or hide it, Set scale, straighten and rotate, crop and brightness, and Reset All. Photo shown / hidden at the top of the panel hides the photo so you see only the drawing; the same switch is the Photo row at the top of the Layers panel.

Part only, beside it, shows only the traced part of the photo: everything outside the part’s closed outlines is covered in the colour of a hidden photo, with a thin margin kept round the outline so its edge is not cut off. A closed outline, circle, ellipse or closed curve counts, and so do lines and arcs that join up into a loop. Nothing is deleted; tap it again for the whole photo. It is one switch for the whole part, it is saved with the project, and the loupe shows it too. The same switch is the chip in the Photo row of the Layers panel. A view with nothing closed drawn on it shows its whole photo, and shapes on the add-on or on a layer left out of the 3D model do not count as the part. Nor does what Offset drew round the part, or a copy of an imported part’s outline: the photo shows the part itself, not the geometry drawn round it. An outline you drew with Offset still counts when it is the part’s edge: when it joins up with lines of your own, or when shapes of the part lie between it and the outline it was drawn from (a circle offset out to the rim, with bolt holes between). An opening through the part is hidden too: a shape its 3D model cuts all the way through (set to Through in the 3D screen’s Shapes), such as the space inside a padlock’s shackle, shows no photo, with the same thin margin kept round its edge.

Make views agree is the last entry in the view list at the top (it appears once the part has two views, with a warning sign when they are more than 10% apart). Two views that show the same side of the part should measure it the same, and one press makes them agree and says in a line how it went, with the part’s size; anything that needs you (a question, a stray shape) shows under it, and What it did opens the full account. It decides from how each view’s scale was set. Where two or more views were photographed on the reference sheet, they are first corrected for how high the part stands above the paper (each tells the others how high it stands): the sheet sets the scale of the paper, and the part’s outline, being closer to the camera, reads a few percent big (a part stood on end, as much as a third). Then every other view is made to agree with the one whose scale is most trustworthy. In order: a view drawn to size (a blank sheet, or a drawing); a view you corrected with Set scale; the reference sheet; a scale measured when the photo was added. A view that borrowed its scale from another always follows, and a view you corrected with Set scale is never changed by the height correction. When two views were scaled the same way and still disagree, it cannot know which is right, so it asks, and shows what the part would measure each way. If a view still disagrees in its other direction afterwards (a photo taken at an angle), it offers Squash to fit, which gives that view a separate scale across and up-down; circles on a squashed view become ovals. It does not offer it once it has worked out the cameras (below): the outlines then differ for a reason the 3D model already allows for. Where a view is drawn as separate shapes (a wheel, its fork, the stem above them), it also works out how far each camera stood from the part, from how each piece measures on the views that show it: a piece nearer a camera looks bigger in that photo, and one further away smaller. It says how far each camera was, and the 3D model then sizes every piece for its own distance, so you can trace the photos as they are. It only does this where the pieces clearly disagree in the way a camera makes them; a tracing already true is left alone. It also notices a photo held a few degrees off straight: pieces nearer that camera and further from it then land a little apart across the photo (seen from above, a stem off its fork’s centre line), and it says which photo and by about how much, and the 3D model moves each piece back where the other views put it, so you trace that photo as it is too. A piece that runs toward or away from a camera, like a fork’s legs running down from its plate, is put right point by point: from above, the legs’ far ends look smaller and lean in, and the model stands them up where the view that bends them least (the front) has them. A small shape drawn well away from the part (left over from an earlier trace) is left out of the view’s size, and it says so. The view it trusts keeps its size: where its scale was measured with two points (when the photo was added, or with Set scale), the piece you measured keeps its size exactly, otherwise its largest piece does. The optional box under it, Correct my drawings and photos, resizes your traced shapes the same way, so the drawings match the model, and moves each piece of the photos with its lines, so the lines still sit on the photos and the photos on the 3D model land on every piece. The thin gaps a piece leaves when it shrinks are filled in smoothly from what is around them; everything outside your traced shapes stays as it was. Untick My photos too to correct the drawings alone: they will then no longer sit exactly on the photos, and Correct my photos too brings the photos along afterwards. One Undo (top bar) puts the drawings and the photos back. Undo puts back everything one press changed, the answer to its question and the cameras included. Undo and Done sit at the foot of the popup; Done, the close button, a tap outside the popup or Escape closes it. More options keeps the separate tools: the measurements side by side, Match every view to one you pick, True size on its own (it shows the part’s size and asks first), and Revert, which undoes the last scale change of any of them, one at a time. With no lens data in the photos a standard phone lens is assumed for the height correction, and it says so. The app also checks quietly when you switch views or close an outline, and says so in the status line when the views are more than 10% apart.

• Set scale (first in the panel) — Click two points on a known dimension and enter the real distance. Works whether or not a scale was set earlier.
• Straighten — Click two points along an edge to align it horizontally or vertically.
• CCW / CW — Rotate 90° increments.
• Crop — Drag corners/edges to define crop area. Rotation handle for angled crops. Click Apply Crop to commit.
• Brightness — Brightness and contrast of the photo. Changes are baked into the DXF.
• Your tracing moves with the pixels. Rotate or Straighten and everything you have drawn — geometry, dimensions, text, detected contours — is carried across with the image instead of being thrown away. Undo history is cleared at that point, because those entries belong to the old image.
• Reset All — Undoes the crop and the brightness/contrast. A crop stays once the photo has been straightened or turned 90° after it; Reset All then resets brightness and contrast only, and Crop is free to use again.

Dimension

Click Dimension in the bottom bar. The panel runs top to bottom: the Dimension tools, Measure only (next section), Clear (Undo the last dimension, Clear All, Clear Measure), and Settings at the bottom (Units, Text size, Decimals). With no scale set, a banner at the top offers Set scale.

• Ortho: Click 2 points, then click to place a horizontal or vertical dimension.
• Aligned: Click 2 points, then click to place a dimension aligned with the line between them.
• Angle: Click two lines, then click to place the angle arc.
• Radius: Click a circle or arc, then click to place the leader.
• Move: Drag dimension points (green handles) to reposition measurement references with snap support, or drag text (orange handle) to reposition the label. A text or a leader moves the same way: drag its words, or a leader’s green tip. Each move is one Undo.
• Text: type in the box that opens, set the Height (how tall the capital letters are, at real size), then tap where the text starts. Tap a text with the tool on to change its words or height as you type; Delete removes it and Done lets it go. Several lines are fine.
• Leader: a note with an arrow. Type the note, tap what it points at (the tip snaps to your drawing), then tap where the note goes.

Dimensions sit on their own Dimensions layer, texts on a Text layer and leaders on a Leaders layer, never on a layer of the part: set each one’s colour and line weight from its row in the Layers panel. Text and leaders are written in one clear font (Arial) that every CAD program reads, and need no scale: without one they are sized to the picture. Text size sets how big dimension labels are. Decimals sets their precision. All of them go into the DXF, on the DIMENSIONS, TEXT and LEADERS layers.

Measure only

The Measure only group in the Dimension panel reads a size off the drawing without placing a dimension:

• Distance: Click two points to measure real-world distance.
• Angle: Click endpoint → vertex → endpoint to measure an angle.
• Radius: Click three points on a curve for radius and diameter.
• Element: Click any traced geometry to see its dimensions. For circles, shows diameter, radius, and circumference.
• Area: Click a closed shape (circle, closed curve, or connected loop of lines/arcs) to calculate area.
• Σ Length: Select geometry with the Select tool, then click this button to sum the total path length of all selected items. Shows per-item breakdown when multiple items are selected.

Multi-View Parts

Capture up to 6 views (Top, Front, Back, Left, Right, Bottom) of the same part.

1. Process your first photo normally.
2. Click + View in the top bar.
3. Each view gets its own perspective correction and scale. If this photo has no reference in it, leave Scale from the top view ticked in the Add View dialog; once both views are traced, the app measures the scale from the dimension the two views share. Rescaling a view that borrowed its scale asks first.
4. Use the view dropdown to switch between views.
5. Download combines all views into one DXF, and the 3D button builds a 3D model from them (next section).

Relabel or delete a view: the pencil beside the view dropdown lists the six labels; picking one another view has swaps the two, which is the usual fix for a front and back shot the wrong way round. Delete view is at the bottom of the same list, and says how many shapes go with it. A view made from a face of the 3D model is renamed there instead.

Copy a side onto another: when you add a side, the Add View dialog offers to build it from a view you already have (pick it in From) — the photo, the drawing, or both. Mirrored flips it left for right, for a part symmetric across the middle; it is offered first for the opposite side. Turned keeps the picture as it is, for a part that looks the same turned round to that side, like a round part. Tick Also onto to put the same copy on the other free sides in one go: a round part’s one side photo then covers its 3D model all the way round. Untick both for an empty view at that view’s scale to draw on by hand.

A side with no photo: press Draw it without a photo in the Add View dialog to add any side as an empty sheet, at the scale of the view your part was measured on, and draw it by hand — a thickness you measured with calipers, say. The other view’s lines are shown on it (Layers › Reference) so you can draw between them. It counts in the 3D model like any view, at the size you drew it. There is no photo on it, so Detect and the Photo panel are not offered there.

How to lay each view out matters, because the 3D model and the 3D DXF place each view by its label. The Add View dialog shows it for you: your part as a box, in its own proportions, with every view you have added on its side the way the 3D model will place it, so a view shot upside down or mirrored looks wrong there before you build. The side you are adding is lit, with the camera where it stands, and a sentence says how to point the part. Drag the box to turn it; tap a free side to pick it. Once you choose a photo, it goes on that side of the box, placed the way the 3D model will place it, and the box closes in on it: press Turn left or Turn right until the part’s top face is up (on the top and bottom views, until its front edge is at the bottom), or tap another free side if the photo is of a different side. To see the other sides for reference, zoom out: pinch the box, or press − on it (+ closes in again); tapping the photo jumps between the whole box and the photo. Upload & Process sends it turned. Some browsers cannot open a HEIC photo before it is uploaded; it is sent as it is then, and the rotate buttons at the top of the next step turn it. Building a side from another view, the box shows the copy, turned or mirrored, before you make it. In short, the front is the bottom edge of your top photo and the back is the top edge; a side view is shot straight on with the part's top face toward the top of the frame.

Smart Trace cross-checks a later view against the earlier ones and offers to relabel it if the measurements do not fit the side you chose. Nothing can tell front from back or right from left by measurement alone, so it names the pair and lets you pick.

Both DXF layouts line the views up by what you traced, not by the photographs. The 3D layout puts every view on the face of the part it looks at; the 2D sheet is a third-angle drawing, so the top view sits straight above the front view with the part in the same place across, and the side views sit level with it. The bottom view is turned upside down there, with the part’s front toward the front view, as a third-angle bottom view is drawn. Your part is somewhere different in every frame, so the photos themselves say nothing about where it is; the drawing on each view does, and the photo rides the same shift as the drawing — so the picture stays under its own outline. A view you have not traced yet is centred instead, which is the most the layout can honestly do with it.

The photos go into the zip beside the DXF and it refers to them by name, so keep them next to the .dxf or your CAD shows an empty frame. Each view carries its whole photograph by default, which makes a large sheet and, in 3D, planes that run through one another; tick Crop photos to the traced part in the Download dialog to trim each one down to what you drew, plus a small margin. Either way the drawing lands in the same place.

3D Model (STEP, 3DM, STL, OBJ & 3D DXF)

Two or three traced views are enough to build a solid. Press 3D on the bottom bar, beside Download: the model is a step of its own, not part of the download. Nothing is written to a file until you have turned the model over and pressed Save model, and you can go Back to the drawing and return as often as you like.

What you need: at least two completed views that between them show the width, length and thickness (top and right, or top and front), each with a scale set. Views labelled with a side the model cannot place are skipped, and the preview says which.

• One model, five files. What you see is a true solid with real faces and edges, and traced fillets as true arcs rather than a fan of chords. Save model asks which file you want, and all of them come from those same outlines: STEP for CAD (in mm, which your CAD converts), 3DM (.3dm) for 3D modelling programs, as one finished solid, STL for printing and viewing (in your drawing units), OBJ for any 3D viewer, or a 3D DXF with the model as a mesh and every traced curve on layers that start switched off.
• Photos on or off. The Include the view photos box in that dialog decides whether the files that can carry a picture do: the OBJ packs the photos into one image mapped onto the model, and the 3D DXF places each view’s photo on the face it shows, clipped to the traced outline, on its own layer. STEP, STL and the 3DM file cannot carry a picture, so the box does not change them.
• The 3DM file is the finished solid. When the server has the CAD kernel, the .3dm opens as one closed solid with every through-cut, recess and boss already applied — the same solid as the STEP, translated face by face, so it opens as the finished part with nothing left to subtract. The editable pieces still ride along on hidden layers: the body and bosses as true extrusions (Extrusions), the other views’ prisms (Prisms), the recess and side-view cutters (Cutters), every traced curve on its face (Curves), and the kernel’s tessellation (Reference mesh). Without the kernel the file falls back to that extrusion layout with the body on the Solid layer, and the cutters wait there to be subtracted. STL and OBJ are only meshes and can never be solids; this file is one. It is written as a version 7 .3dm file, because the .3dm format only reads forward — a program that reads version 7 cannot open a version 8 file — and nothing in this export needs anything a newer version added, so anything that reads version 7 or later opens it. The Save model tooltip and Details both say which version the file is.
• If your server has no CAD kernel the preview falls back to a voxel hull, which has a stepped skin on every curve. The headline says so, Details gives the reason, and the STEP option is greyed out; STL and OBJ still save.
• The bottom bar holds the modes. Shapes, Faces, Edges, Simplify and Display (and Parts and Pieces when the model has them) each slide a panel up over the bar; tapping a lit one puts it away again. Below them are Back to the drawing and Save model. Undo, Redo and Revert sit on the title row beside Details. While the model builds, the stage shows a spinner and how long it has been working; only one model builds at a time, so a second request waits its turn and says so.
• Turning it over. Drag to tumble, pinch or scroll to zoom, two fingers (or a right-drag) to pan, double-tap to re-centre. Put one finger down and hold it still, then drag with the other, to spin the model about that point; on a mouse, Shift-drag does the same.
• Shapes: select, set, apply. Tap Shapes on the bottom bar and every closed shape you traced inside the part, including one drawn up against the outline with edges on it, is laid over the model. Tap the ones you want (All, Circles and Face pick several at once, Clear starts over), choose a direction — leave it, cut it through, recess it by a depth, cut it through except for a floor of a stated thickness, or raise it into a boss — and how far, then press Apply. Nothing is rebuilt until you do, so you can set one group, apply, and move on to the next. Depths are in your drawing units, measured from the part’s own surface under the shape — a recess into a sloped face is that deep everywhere and a boss stands on the face wherever it is — except Through, leave, where the amount is the material left under the shape: a wall of that thickness offset from the part’s far surface, measured straight through the wall, so it follows the far surface and a sloped or curved underside keeps the same thickness everywhere (a blind pocket dimensioned by its floor, like shelling one shape). Leave more than the part is thick under it and nothing is cut; the preview says so. Shell, open is the whole-part version: the selected shapes become openings cut straight through the wall of their face, and everything else is hollowed to a wall of the amount you enter, the same thickness everywhere, measured through the wall — a housing with its lid opening, or a tray. It runs after every other extrude, so recesses and bosses are part of the surface it shells; several shapes are several openings in one shell, and where the part is thinner than twice the wall there is no hollow to make. It works from a face view too, which is usually what you want on a hood or a cover: Through, leave there leaves its material against the far surface measured along that view’s own direction, so on a hood it leaves one wall and nothing where the far surface is somewhere else, while Shell, open leaves the same wall everywhere and opens the face you drew on. Undo, Redo and Revert on the title row walk back the extrudes you applied (Ctrl+Z / Ctrl+Y while the preview is up); Revert takes every one off and shows the plain outline again. With an add-on body in the drawing the panel works on ONE body at a time, chosen by the Part / Add-on row at the top of it: the count, what is laid over the model, All, Circles, Face and Apply are all that body’s, so pocketing the shroud can never cut the part underneath it. Tapping a face of a body in Faces switches the panel to it, and the line beside Apply says when the other body has shapes set too. On a part built from separate pieces (a wheel in a fork, say), an On choice under Apply says which pieces the cut goes into, and they are tinted orange: the piece it is drawn on (a shape drawn on the wheel goes into the wheel, not into the fork crossing in front of it), the whole model (everything under the shape, as before), or any one piece. A new shape starts on the piece it is drawn on. This needs the CAD kernel; without it the preview cuts the whole model and says so. A setting stays with its shape when you draw, delete or array other shapes on that view afterwards; if you delete the shape itself, its setting goes with it and the Details say so.
• An add-on body: a part built to fit this one. In the Layers panel, hold a layer’s 3D chip to make it an add-on body (the chip reads 3D+). Draw the new part — a shroud, a bracket, a cover — on those layers, on the same views as the original, and the 3D step builds it as a second solid standing exactly where you drew it over the part: the original keeps its photo, the add-on is shaded plain so you can tell them apart. It takes Through, Recess and Raise from the Shapes panel like the part does. Subtract the part (a row in the Shapes panel) cuts the original out of the add-on so it fits over it exactly, with a clearance you choose taken off the add-on; Apply rebuilds, Undo puts it back. Every file carries both bodies, never fused. It needs the CAD kernel, and its outline on at least two views.
• Edges: fillets and chamfers. Tap edges of the model to select them (tap again to drop one), choose Fillet for a rounded edge or Chamfer for a cut-back one, type the size and press Apply. They are applied after every pocket and boss, which is where a CAD package puts them too, so they round the edges those left behind. An edge is remembered by where it IS on the part, not by a number, so it survives a rebuild after you change an outline — and a pick that can no longer be found is reported and left alone rather than rounded on the wrong edge. A radius too large for its edges is refused and said so, and the model comes back without that one. You can only pick an edge you can see: one hidden behind the model — the far side, or the inside of a hollow body — is not offered, and a tap there says so. To reach one, turn the model, or switch Display to Wire or Ghost, where every edge is drawn and every edge can be picked. In the Edges panel the edges you can tap are drawn faintly over the model, and the ones you have picked in bright cyan. Undo, Redo and Revert walk these beside the extrudes as one history, and the project file carries them. Fillets need the CAD kernel: on a server without it the model is the voxel hull, which has no real edges to round.
• Display: Outline to views. The 3D model's own outline, as each view sees it, drawn back onto every view on a new model outline layer (the add-on's on add-on outline). It is how rounded creases, pockets that break through and anything else the model changed come back into your 2D drawing: a rounding that bends the outline from a side shows as a round on that side, a hole as an inner ring. Your own drawing is left exactly as it is — the outline sits beside it, its layers stay out of the 3D build, and they go into the DXF like any other layer. Drawing it again replaces it; one Undo takes it off every view.
• Edges: round the creases where the views meet. The model is every view's outline pushed through the part and overlapped, so wherever two views' outlines cross there is a sharp edge nobody drew — the awkward ridges and three-way points at the corners. Choose Creases in the Edges panel, type a radius and press Apply; there is nothing to tap. The server finds every such edge and rounds as many as it can: all at once if it can, otherwise the largest set that will round together, with a crease too tight for your radius getting half or a quarter of it. The preview says how many it rounded, how many at a smaller radius and how many stayed sharp; a smaller radius usually reaches more. The creases are rounded before any pocket or boss, as part of the outer shape. To do it, a hand-traced outline is read as a smooth curve held within 0.1 mm of the points you traced, which also takes the flat facets off the part. Applying it again with another radius replaces it, Undo takes it off, and with an add-on body a Part / Add-on choice says which body's creases to round. This needs the CAD kernel, and on a big hand-traced part the rebuild can take a few minutes.
• Simplify: fewer faces, by drawing the outlines with fewer points. A hand-traced outline of sixty short segments caps the part with sixty facets, which is why a flat-looking top can come back split into several faces — the model has exactly as many faces as your outlines have segments, so merging faces afterwards cannot help. The slider says how far an outline may MOVE; the line under it tells you what that buys before you commit (“847 → 210 points · moves the outline at most 0.18 mm”), and nothing is rebuilt until you press Apply. Apply redraws each outline on a new layer called <name> (simplified), which is what the 3D model is then built from, and leaves the original layer exactly as it was — hidden on the canvas so the part does not draw twice, and switched out of the 3D model with the same 3D chip you can use by hand in the Layers panel. Nothing is destroyed: Restore full detail removes the simplified copies and brings every original back. Both layers go into the DXF, so your CAD opens the measured outline and the simplified one side by side and you can switch either off there. Applying again at a different setting always starts from the full-detail originals, so you can feel for the right amount. When the drawing has an add-on body, a Part / Add-on row appears at the top of the panel: they are different drawings of different things, so you simplify one at a time and each keeps its own setting — simplifying the shroud never un-simplifies the panel under it, and Restore puts back whichever one you are on.
• Parts: the imported parts in the model. Every part you imported and have shown in the drawing is a body of its own in the model, built as its own project builds it — with the pockets, bosses and holes its own Shapes panel applied, the shapes drawn on its face views, and its fillets and chamfers — at its true size, placed exactly where it sits in the views, in the colour it has there (and with its photos in Photo). The row says what came with it; a part imported before this could come along says outline only, and importing its project again brings the rest. A part’s body is built in the background right after it is imported and kept, so a 3D build with a detailed part is not slowed down by it every time. The Parts button appears on the 3D bar when there are any. For each part choose Keep (it sits beside the housing as its own object), Cut out (it is taken out of the housing with the clearance you type, so the housing fits round it) or Merge (it becomes part of the housing), then press Apply; nothing is rebuilt until you do. The housing is the add-on body when the drawing has one, and your own part otherwise — so in a blank project the part you draw round the imported ones is the housing. A part that does not touch the housing is kept on its own rather than merged, and the row says so. A part needs its outline on at least two views showing all three sides to be a body; one that does not is listed and left out of the model. Kept and cut-out parts are separate solids in the STEP, separate objects in the OBJ, and on their own layers in the 3DM file and the 3D DXF (with photos on, the 3D DXF lays each part’s own photos on its faces too); a part hidden in the drawing is left out of the model. Undo, Redo and Revert walk these with the extrudes, the project file carries them, and they need the CAD kernel. A cut or merge is applied after every pocket and shell on the housing; the edges it leaves — the rim of the pocket a part is cut out of — can be rounded in Edges like any other, and those rounds are made after the parts are.
• Pieces: fix a piece made from the wrong shapes. When a view’s shapes do not join into one outline, the model is built piece by piece: each shape matched with its partner on the other views by where it sits. A shape with nothing to match on a view fills that view’s whole outline, and can stand out as a block nobody drew; the 3D Details name it, and the Pieces button is lit orange. Tap Pieces, then a piece of the model: it is tinted, and the panel says which shapes made it. Tap the same spot again for the next piece there. Match to… opens each other view’s photo with its shapes outlined (orange is what the piece is matched to now): tap the shape it really is. Make it round spins it round the centre line of the round piece it lies across, such as a hub on its wheel’s axle; this needs the CAD kernel. Leave out takes it out of the model; the panel lists what is left out, with Put back. Each fix is one Undo, Revert takes them all off, and the project file keeps them. A fix belongs to its shape: redraw the shape and the fix no longer applies, and the panel says so. When the model is more than one body, the 3D Details say how far apart the nearest two are.
• Round: a part that is round. When one view's outline is a circle (a wheel, a housing or a knob seen from above), a side view that runs through its centre shows the part's profile. Where that side view is the same on both sides of the centre, the model spins it round the centre, so the part comes out round all the way round instead of square-sided, and the 3D Details say so. The Round button sets it by hand: Auto decides as above, Round spins the side views even when they are not quite the same on both sides (the larger half is spun), and Straight pushes every view straight through, with nothing spun, a part made of separate pieces too. Spinning needs the CAD kernel. One Undo takes the setting back, and the project file keeps it.
• Display: four ways to look at it. Solid is the finished surfaces, shaded. Ghost draws the model’s own edges over a see-through body, so a pocket on the far side is visible without turning it over. Wire is those edges alone, see-through — every edge of the model at once, including the far side, with nothing hiding anything. A drawing rather than a picture, and the quickest way to check a corner really is an arc. Both read the edges the CAD kernel produced, so on a server with no kernel (a voxel hull) they are greyed out: a mesh has triangle borders, not the part’s edges. And Photo: each face wears the photo of the view that shows it, lined up with the outlines you traced. The quickest way to confirm the top really is the top. STEP and STL cannot carry a picture, so for them it is display only — but OBJ + photos saves exactly what you see, as a zip you can open in any 3D viewer. Where the drawing has an add-on body, a Show row lets you switch either body off on screen — hide the add-on to work on the part underneath it, or the reverse. It is display only: every file you save still carries both, and picking follows what is on screen, so a body you have hidden cannot be tapped. With imported parts in the model, a Parts button there hides or shows them all the same way.
• Faces: draw on the model itself. Tap Faces and then a flat face of the model — the top, an end, a chamfer, the floor of a pocket you already cut. The panel names it, gives its size and says how far it is tilted, and New view from this face makes a new view standing on it: a blank canvas at the part’s own scale with the face’s outline already drawn on it. Draw pockets, bosses and holes on that outline exactly as you would on a photographed view, then tap 3D again and they are cut into the model along the face’s own normal — so a pocket in a 32° chamfer goes straight into the chamfer, which no combination of top, front and right views can express. Shell, open works from a face view as well: the shape you drew becomes the mouth and the body is hollowed to a wall of the thickness you enter — the same thickness all round, which is what a hood or a cover wants. Copy the photo puts the photograph on that canvas so you can trace features straight off it: the app picks whichever of your views looks at the face most squarely, warps its picture onto the face’s own plane and cuts it to the face’s outline, so what you see is to scale in the face’s own millimetres and a length traced off it is the part’s length. The box says which view the picture would come from and how far round it is; past about 45° it says the patch is stretched, because a camera that oblique sees the face foreshortened and the warp can only stretch what it saw. A face no camera sees at all gets a blank canvas and the box says so rather than turning itself off. The add-on body was never photographed, so its faces are always blank. The face’s own outline is ordinary geometry you can work from — select it and Offset to get a line a fixed distance in from the edge, snap to its corners, measure off it. Offsetting never changes the outline itself; it makes a new shape beside it. The outline is what says which of your shapes are on the face, so it keeps its own face outline layer: a shape only has to OVERLAP the face, so a pocket drawn right to the edge still counts and one that breaks out over the edge is cut where the part is; a ring drawn right round the face is a boundary rather than a pocket over the whole of it and is ignored, a shape drawn beside the face is left out and the preview says so, and if you delete that layer it says that too instead of guessing. The view is listed with your other views and can be renamed with the pencil beside the view list; it has no top / front / right label, because its plane is what places it. Curved faces cannot be drawn on flat and say so. A flat-looking face is often several facets a degree or two apart — a hand-traced outline caps the part in short runs, so the flat top of a real part is rarely one face — and a tap takes the whole flat area rather than the piece under your finger; the panel says how many facets it is and its tooltip how flat their average plane really is. The model itself is untouched: every facet is still in the STEP, the 3DM file and the mesh. The add-on body has faces of its own: tap one and the panel says Add-on face, and everything you draw on the view it makes cuts the add-on, never the part. Edges works the same way — an edge picked on the add-on is rounded on the add-on — and picking edges on both at once simply makes one fillet on each. This needs the CAD kernel on the server: on a voxel hull there are no flat faces to pick, and a shape drawn on a face is in the STEP and the 3DM file but not in the fallback mesh, which the preview states rather than pretending otherwise.
• Shapes you leave alone still travel into the STEP file as sketch curves on the right face, so the geometry is there to work from even where you did not cut it. STL and OBJ are triangles only and cannot carry them.

It is a visual hull — the solid your views have in common. A pocket that is a hole in one view and solid in the others cannot be expressed by that, which is what the inner-shape controls are for. Where a view is drawn as separate shapes that do not join into one outline — a wheel standing clear of its fork, say — each shape is matched with its partner on the other views by where it sits (the fork with its arm, the wheel with the wheel) and each group is built as its own piece, so the spaces between your shapes stay empty. A shape drawn as a circle on one view makes its piece round: its outline on the other views is spun round the circle’s centre, so a wheel is a tyre all the way round and a post a true cylinder, and a piece centred on that line with nothing drawn where the circle is (a hub across a fork) is spun with it. (The voxel preview, shown only when the true solid cannot be built, keeps their straight sides.) A piece one view cannot see — an axle hidden under the fork from above — is matched with the shape drawn at its end on another view (the nut on the wheel), even a few millimetres apart, and built from the views that show it. A shape drawn across a whole view is fitted to the length of its partner on the other view, so what it shows lines up with it, and a loose shape drawn touching another (a fork’s leg drawn on its own) is built as part of it. Once Make views agree has worked out how far each camera stood, each of those pieces is also built at its own distance from the camera: a piece nearer the camera looks bigger in its photo, so you trace the photo as it is and the model sizes each piece true. A photo held a few degrees off straight is put right the same way: each piece is moved back where the other views put it. A piece that runs toward the camera (a fork’s legs, running down from the plate above) is put right point by point, each part of it at its own distance, so legs that lean in on the top photo stand straight in the model. Correct the photos too (in the same popup) and each piece’s photo lands on its piece in the model. No photograph is exact to the millimetre, so where two views put the same edge a hair apart (within about half a percent of the part) it is lined up at their average before the model is built, and only what lies close to that edge moves with it: two pieces that touch in your drawings then touch in the model, and a step shows once, not twice. A view drawn to size never moves; the photographed views come to it. Views photographed on the reference sheet are corrected for how high the part stands above the paper; a view scaled by hand (two points, a typed width) is used as measured. The preview states the size it settled on and, behind Details, everything it had to assume: which views disagreed, whether the height correction was used, how many edges were lined up, whether a view was turned or its outline wrapped around loose pieces, how many pieces its separate shapes made, and how far each camera stood when its pieces were sized for it.

Exporting the model needs a verified email address and a Pro or Studio plan. A one-view DXF downloads free; a multi-view DXF needs a plan too.

File: Save, Save part only, Open, Rename, Import part, Import DXF, New Part

The File button (first on the left of the top bar) holds everything that acts on the whole part. Save your work as an .lcad project file to resume later or share with others.

Saving: File › Save project. This downloads an .lcad file containing your photos (compressed, at full resolution), corrections, all traced geometry, dimensions, scale settings, layers and colour preferences.

Save part only (File menu) saves a smaller copy with each photo cut to the traced part, the same way Part only shows it: the rest of each photo is saved as white. The drawing, scale and 3D settings are all kept. The copy is named …_part_only.lcad, and the project you have open is not changed. A view with nothing closed drawn on it keeps its whole photo. An opening the 3D model cuts through is left out as well. The part is kept at full resolution; only the background is left out.

Loading: File › Open project, or Load Saved Project on the upload screen. With a part already open it asks first, because opening a project closes it. Everything restores — geometry, scale, layers, colours, snap/guide settings, reference views, and everything you did in the 3D model: the extrudes, fillets and chamfers, the add-on fit, Simplify, and the display mode. A large file shows how much has uploaded; on a poor connection it says so if the upload stalls or drops.

Note: Loaded views open in Draw mode. You can't go back to re-edit perspective or scale on loaded views, but you can add new views with + View and those have full editing.

Rename project (File menu) changes what the project is called: the saved .lcad, the downloads and each view's DXF. The menu shows its name now. A photo uploaded without a name is called by its file name (IMG_8322.jpeg) until you rename it, or take the name Smart Trace offers.

Import part (File menu) brings a saved part (.lcad) into the project you have open, as a fixed reference to build around: several traced parts put together, then a housing drawn round them. It is a copy, not a link: changing the part’s own project later changes nothing here. It comes in at its true size in every view, drawn in its own colour, with its photo cut to the traced part (the photo can be switched off); an opening its own 3D model cuts through, like a padlock’s shackle, is cut out of the photo too, so what is behind shows through. A part imported before this came in with the opening still in its photo; it is cut out the next time the project is opened. Your drawing snaps to it and guides line up with it, but the editing tools never reach it: it cannot be changed, moved by them or erased. Its outline can be picked in Select as a reference to Offset or Copy into your own drawing; a part drawn in pieces is picked by its whole outline first, so Offset draws one clean ring round it. It sits in one place for the whole project: in Layers › Imported parts, Move drags it on the canvas along the view’s two axes (it snaps to your drawing and to the other parts), or, tapped again, moves it point to point or by a typed distance, and every other view follows; Turn turns it a quarter turn clockwise as seen in the view you are on, and Rotate turns it by any angle, by a pivot and a reference point or a typed angle. Where the part has a view this project lacks, that view is added as a blank sheet at the same scale. Where the part has no view of the side a view faces, or a view sees it turned at an angle, that view shows the part’s opposite side seen from behind (its outline, no photo) when it squarely faces away, or else its 3D body seen from that side, wearing its photos, with its outline dashed. Any number of parts can be imported, and the project file carries them. Save part only on the part first makes the import smaller. At Download you choose whether the imported parts go into the DXF, each on its own layer. In the 3D model each shown part is a body of its own, at its true size, where it sits in the views, and it brings the pockets and rounded edges its own project gave it — see Parts in the 3D section.

Import DXF (File menu, or the upload screen) reads a DXF drawing: lines, circles, arcs, polylines with their arcs, ellipses and splines, with blocks exploded. Dimensions, text, hatches and images are left out and the import says how many. Each DXF layer becomes a layer here, and a CAD DXF comes back on its own layers. With a part open you choose Onto this view (at the view's scale, centred on the screen and selected so you can move it; the view needs a scale) or As a new part (a blank canvas the size of the drawing). A file that names no units is read in the units selected on the upload screen.

New Part (File menu) asks before clearing anything, and says how many shapes you would lose; save the .lcad first if you want this part back.

Blank Canvas Drawing

Click Draw on Blank Canvas on the intake screen to create a drawing without a photo.

• Choose canvas size: Letter, Tabloid, A3, A4, or Custom dimensions.
• Select units (inches or millimeters) for the canvas.
• Use all the same Draw tools — Polyline, Curve, Circle, Rectangle with dimensional inputs.
• W×H mode: Type exact width and height for rectangles. Click to place.
• R/D mode: Type exact radius or diameter for circles. Click to place at center.
• L mode: Type exact segment length for polylines.
• Multi-view is supported — add views from the top bar.

Navigation & Shortcuts

Type a command. With a keyboard (a computer, or an iPad with one attached), start typing any tool's name with nothing selected in a box: Polyline, Move, Offset, Fillet, Dim, Crop, Save. A list of matches appears as you type, short names work too (L, M, O, J, X), and Enter, Space or Tab starts the top one. Arrow keys pick another, Escape closes it. Enter with no tool running repeats the last command. Not shown on phones.

Number boxes take units and math. A plain number is in the box's own units. You can also type another unit (25mm, 1/2", 2in, 1.5m), feet and inches (13' 6", 5ft 3in), or a sum (13x12, (2+3)*4mm, 10/4). It is worked out when you press Enter or leave the box, and the answer replaces what you typed.

Zoom: Scroll wheel or pinch. Anchors to cursor. Max 50×.

Pan: Space+drag, middle mouse, or two-finger drag.

Leaving a tool. Tap a lit tool button again to put it down and return to Select. A button with several modes (Circle, Rectangle, Edit Pts, Mirror/Symmetry, Scale, Align) steps through each mode once, and the next tap leaves it. If work is waiting on the ✓, you are asked first.

Keyboard shortcuts:

• Ctrl+Z — Undo last action
• Ctrl+Shift+Z / Ctrl+Y — Redo
• A letter — Opens the command line (desktop and iPad with a keyboard); type a tool's name and press Enter
• Enter — Finish polyline or curve; with no tool running, repeat the last command
• Escape — Cancel what is in progress; press again to leave the tool for Select, and again to deselect
• Delete / Backspace — Delete selected geometry; while placing points, take back the last point
• Ctrl+C / Ctrl+V — Copy / Paste
• Ctrl+A — Select all
• [ ] — Decrease / increase brush size
• Ctrl (hold) — Momentary ortho toggle
• Shift (hold) — Momentary snap toggle
• Alt (hold) — Momentary guides toggle
• CapsLock — Tap to toggle the loupe on/off; hold to show a hover loupe under the cursor without clicking
• Space (hold) — Pan mode (drag to pan)
• Right-click — Delete point in Edit mode. In Select mode, opens a popup to pick between overlapping geometry.
• Long-press (mobile) — Same as right-click: pick between overlapping geometry when objects are stacked.

Troubleshooting

• Perspective correction looks wrong: Check that you clicked points accurately. In Corner mode, the corner point (◆) must be exactly where the arms meet. Use the Loupe for precision placement.
• Grid or straight lines still look wavy after correction: This is lens barrel distortion, not perspective. Calibrate a lens profile at the Camera Calibration page for your specific lens.
• Scale is off: Use Dual Rulers for best accuracy — it corrects independent X and Y scale. Verify with the Measure tool on a known dimension.
• Detection misses shapes: Use the Guide Brush to focus detection on specific areas. Improve contrast — dark object on light surface works best. Adjust Threshold and Detail sliders. Avoid shadows across the subject.
• Reference sheet not detected: All 4 markers must be fully visible. Ensure good, even lighting with no glare on the sheet. If you can see all four and it still fails, use Place corners by hand (see Reference Sheet).
• Large objects are distorted: Stand back and use telephoto (2×). Avoid ultrawide lens. Crouch to mid-height of the object.
• Far legs / far edges look wrong on furniture: This is parallax — the near parts physically blocked the far parts from that camera angle. Shoot more head-on, or accept that a single photo can't capture deeply hidden geometry.
• Lens Correction: Most iPhones pre-correct JPEGs. Leave at "None" unless you've calibrated a custom profile. If using a profile, always download a .lenscal backup — browser storage can be cleared.
• Missing lens profile: If your profile disappears (browser data cleared, new device), import your .lenscal backup file from the upload screen.
• HEIC files: Fully supported. Avoid screenshots — they strip EXIF metadata needed for lens profile matching.
• The 3D model is the wrong size or shape: Open Details in the preview — it says what it assumed. The usual causes are a view whose outline did not close (draw the part as one closed outline, as closed shapes that touch, which are joined into one, or as separate closed shapes, which are paired across the views; use Clean Up or Snap Corners where pieces do not meet), a view labelled with the wrong side (Smart Trace offers to relabel it, or use the pencil beside the view list), a view photographed a quarter turn round, or leftover shapes drawn well outside the outline (the preview names them; delete them). Make views agree at the bottom of the view list checks whether the views measure the part the same, and fixes it. Turning the Photo overlay on shows which face is which straight away.
• The STEP option is greyed out when you press Save model: Its tooltip says why — that server has no CAD kernel, so the preview is showing a voxel hull instead of the true solid. The 3DM, STL and OBJ still save (the 3DM file needs no kernel; STL and OBJ carry the stepped skin you can see on screen).
• An OBJ opens as four copies of the part, like a cross: some phone viewers turn each material group separately, so the OBJ is written as one material over one image. If it still happens, save the 3DM file instead — it carries a true solid. (Some phone viewers do not show OBJ textures at all; desktop 3D programs do.)
• DXF output: Opens at 1:1 scale in any CAD program that reads DXF. The corrected image is embedded as a background — trace over it or use the exported geometry directly.
• The photo shows as an empty frame in CAD: the DXF refers to its photos by name, so keep them in the same folder as the .dxf when you unzip.
• Reporting a problem: Report issue in the Help header sends us a note with what the app already knows attached. Debug bundle beside it downloads what we need to reproduce it: Small is the drawing only, a few KB, and is what usually works on a phone; Full includes the photos.