The process of converting smooth mathematical surfaces (NURBS, B-rep) into a polygon mesh by approximating them with triangles to a specified tolerance.
Tessellation converts exact mathematical geometry (NURBS curves, B-rep faces) into polygon meshes for rendering, slicing, or physical simulation. The key parameter is chord tolerance (or chord height deviation): the maximum allowed distance between the ideal surface and the approximating triangles. Smaller tolerance = more triangles, better approximation, larger file. Angular tolerance also controls how many triangles are used around curved edges.
CAD tools tessellate at export to STL, OBJ, or 3MF. In Fusion 360: File → Export → STL → Refinement (Fine/Medium/Coarse). For FDM printing, chord tolerance of 0.02–0.05mm is optimal: imperceptible at 0.4mm nozzle resolution, reasonable file size. For SLA printing, use 0.005–0.01mm. In Blender, the NURBS-to-mesh conversion uses a resolution parameter (U/V subdivisions) rather than a tolerance: increase until no visible faceting at print scale.
Over-tessellation (very fine tolerance) produces enormous files (100MB+) that overwhelm some slicers with no visible print quality improvement. Under-tessellation (coarse tolerance) produces visible faceting on curved surfaces in the final print. Tessellation is not reversible: converting STL back to CAD loses the original mathematical surface data. Always keep the native CAD file (.f3d, .sldprt, .step) as the master and tessellate fresh for each print job.
Related terms: NURBS, B-rep, STL, Polygon Count, Mesh Decimation
| Field | 3D design, 3D printing, engineering |
|---|---|
| Also called | mesh tessellation, surface triangulation, faceting |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert