Footprint to 3D Solid Extruder

What it is for

Sometimes all you need is one honest 3D block: an L-shaped desk to check in a room model, a plinth for a sculpture, a printable test solid, or a quick massing shape. Drawing it in full CAD software is overkill. This tool takes a footprint as X,Y points in millimetres and an extrusion height, then builds a closed, consistently wound prism (a watertight mesh). You can set its position, base elevation and rotation around the vertical axis.

The result is a mesh you can download as OBJ or STL, an exact surface area and volume, and an editable Kerfwise Form Studio project. Use the Open in Form Studio link to keep working on it there, add more solids, tag them and save views. Form Studio uses the same geometry engine, so nothing changes on the way.

Footprints must be one simple outline: 3 to 64 points, no holes, no crossing edges and at least 1 mm² of area. Curves, booleans and fillets are out of scope. A circle has to be approximated by a polygon.

Worked example

The default input is an L shape:

0,0
1200,0
1200,400
500,400
500,1000
0,1000

With a height of 600 mm, the tool reported "20 triangles form one closed solid with 0.4680 m³ gross volume" and a surface of 4.2 m². You can check it: the footprint is 1200 × 400 + 500 × 600 = 0.78 m², and 0.78 × 0.6 = 0.468 m³. The perimeter is 4.4 m, so 2 × 0.78 + 4.4 × 0.6 = 4.2 m².

The second example, 0,0;800,0;800,500;0,500 (semicolons work too) with height 180 mm, base elevation 100 mm and rotation 30°, gave 12 triangles, 0.072 m³ and 1.268 m². The rotated corner (800, 0) ends up at (692.8, 400.0, 100), as expected for a 30° turn.

A footprint drawn as a bow tie (0,0 / 1000,1000 / 1000,0 / 0,1000) was rejected with "Footprint edges cross or touch. Use one outline without holes."

How to read the result

• Summary: the triangle count and gross volume. A prism with n footprint points has 2 × (n − 2) cap triangles plus 2n side triangles. The L with 6 points has 8 + 12 = 20.
• Surface (m²) and volume (m³): exact for the polygon you entered.
• Mesh: the vertices after rotation and translation, and the triangles as index triples with outward winding.
• Project: a one-solid Form Studio project. Name and colour come from your inputs.
• Open in app: the link that loads the project in Form Studio for editing.

Tips and common mistakes

• List the points in order around the outline, clockwise or counter-clockwise. Jumping across the shape makes edges cross.
• Repeating the first point at the end does no harm. A closed rectangle entered with five points still gave 12 triangles, because the outline closes automatically.
• Rotation turns the solid around the origin at (X, Y), so place your footprint's reference corner at 0,0 if you want predictable rotations.
• STL has no units. Import as millimetres, otherwise a 1200 mm desk becomes 1.2 mm or 1.2 km.
• For a round table, approximate the circle with 24 to 32 points. Form Studio's Draw circle uses 24 sides.
• Surface includes the bottom face. Subtract the footprint area if the solid sits on the floor and you only need visible faces.

FAQ

Is the STL watertight enough for 3D printing?

Each prism is closed with consistent outward winding, which is what slicers need. Scale it in the slicer if you want a model rather than full size.

Can I make a shape with a hole, like a frame?

Not as one footprint. Build it from several solids in Form Studio, for example four bars. They stay separate shells, and their quantities are gross.

Can I use inches?

The tool's inputs are millimetres. Form Studio can display inches, but its exports are always millimetres.

How do I combine several solids?

Open the result in Form Studio and add more, or use the 3D Form Model Report & Export on a project with many solids.