The idea
Draw the cross-section the way you would in AutoCAD — one line or arc at a time —
and the solver computes its area, centroid, moments of inertia, and section
modulus values. Any closed loop you draw inside another closed loop is
treated as a hollow cut-out automatically.
Skipping the drawing — the scanner
Tap Open scanner in the sidebar, photograph or upload the
cross-section from your textbook, and the AI builds the geometry for you. Make
sure the dimension labels (B, H, t, r) are visible and readable. Use the
Edit vertex and Edit segment length panels to fix any
dimensions the AI got wrong.
The four tools
- Line L — click vertex by vertex. Click near the
first vertex (or press Enter / Close Loop) to close.
- Arc A — click three points the curve passes through:
start, through, end. The arc joins onto whatever segment came before it.
- Circle C — click the centre, then any point on the
circumference. Places one complete closed loop.
- Set Origin O — click the point you want as (0, 0).
Use it after drawing so you can read x̄ and ȳ from any reference corner.
Solid vs. hollow
You don't tag anything — the app looks at how loops are nested.
- A loop not inside any other loop → solid.
- A loop inside one other loop → hollow (subtracted).
- A loop inside two others → solid again (an island inside a hole).
The shaded blue area is the solid part. The unshaded interior of a nested loop is
the hollow part.
Typing exact distances (works on phones too)
The Distance + Angle panel above the canvas is the primary way to
enter precise dimensions.
- Distance only — type the length, leave Angle blank. The line goes
from the last point toward wherever the cursor is pointing, at exactly that length.
Useful for axial segments (combine with Ortho).
- Distance + Angle — type both. The line goes at exactly that angle
(0° = right / +X axis, 90° = up / +Y axis, counter-clockwise positive) for that
length. Polar entry, like AutoCAD's
@dist<angle.
- Tap Apply (or press Enter while a field is focused) to commit.
On desktop you can also just type digits on the canvas — the distance field fills
automatically. Hit Enter or click to commit.
- Hold Shift for one-off Ortho, or click the Ortho
button (or press F8) to lock it on.
Point labels & editing
Every vertex you place gets an automatic label (A, B, C, …). Use the
Edit vertex panel to change a point's exact (X, Y) — every segment
that uses that point follows along. Use Edit segment length to set
a line's length numerically; the end point moves along the existing direction. Both
panels are essential for fixing scan errors after the geometry is imported.
Navigating the canvas
- Pan — hold the middle mouse button and drag on a
desktop, or use a two-finger drag on a phone or tablet.
- Zoom — mouse wheel on a desktop, pinch on touch, or
the + / − buttons.
- Fullscreen — tap the ⛶ Full button on the canvas
toolbar to expand the drawing area to the whole screen. Tap again or press
Esc to exit.
- The X and Y coordinate axes start hidden. They appear after you use
Set Origin so the coordinate system reflects the reference point you chose.
You can toggle them in Grid & display.
Tips
- Lines and arcs chain together: an arc continues from the last
point of the previous segment, so you can mix straight edges and curved fillets in
one continuous loop.
- Use Type exact point for precise coordinates — like an
AutoCAD command-line entry.
- Snap to grid is on by default. Turn it off in Grid & display
for fine adjustments.
- Press Esc to cancel the current sketch, Enter to close it.
