Choose STEP-to-STL tessellation settings with a measured example

Tessellation replaces a CAD surface with triangles. Finer settings can increase triangle count and file size, but the result depends on the surface and the kernel's other controls. Use a representative part and inspect the output instead of treating one tolerance as suitable for every task.

A cylinder with known geometry

Our source cylinder has a radius of 10 mm and height of 20 mm. We hold angular deflection at 1 radian and change absolute linear deflection. Each output is exported as binary STL and reread for verification.

The coarse mesh does not reach the circle's full diameter on every axis: its vertices approximate the circumference. The finer samples reach 20 × 20 × 20 mm mesh bounds in this experiment. A source surface's exact bounds and a sampled mesh's bounds need not be identical.

What the error column measures

For horizontal edges on the cylinder's side triangles, we compare each edge midpoint's distance from the cylinder axis with the analytic 10 mm radius. The largest sampled radial difference is the number in the table. It does not measure every point on the surface, every direction of deviation, or a manufacturing tolerance.

The occt-import-js documentation distinguishes an absolute deflection value from a bounding-box ratio. These preparation controls use absolute millimetres. The report records the requested setting separately from this case study's measured chord error.

Try a setting before committing to it

Preview the mesh, inspect curved regions, and compare triangle count and download size. Keep a setting only when its result fits the receiving application's needs. A very fine setting can require more time and memory; this tool limits input size and triangle count, and Cancel terminates the active worker. If the operation stops, the last completed model remains available. Keep the original CAD source because an STL cannot restore the exact curves later.