Tessellation and drawings

Meshing

ogeom::mesh::tessellate triangulates a shape at a given Deflection: the maximum distance between the mesh and the exact geometry, plus an angular bound.

• The triangulation is stored on the model. Read it back with triangulation_of and polyline_of.
• triangulate returns one welded mesh for a whole shape.
• simplify decimates an existing mesh toward a Target.
• hatch_face cross-hatches a face, for section fills.

One mesh per face

A viewer that picks and colours individual faces needs one mesh per face. Adjacent face meshes must use the same points along every shared edge, or cracks appear (for example where a narrow face samples its edges more finely than requested).

1. Call edge_chords_for once per shape to fix the shared edge points.
2. Call triangulate_face_with for each face using those points.

tessellate stores its faces the same way.

Deflection controls accuracy downstream

Everything that consumes the mesh (mass properties, the mesh exchange formats) carries exactly the error you chose here.

Drawings

ogeom::hlr produces 2D drawings by exact hidden-line removal (not a rendered image).

• project takes shapes and a view direction and returns a Drawing of DrawnCurves. Each curve has:

  • a Visibility (visible or hidden);
  • a Source: the model edge, silhouette or outline that produced it.

  Silhouettes of curved faces are traced on the exact surfaces.

• section cuts a shape with a plane and returns a SectionView with the cut face outlines, ready for hatching.

• broken_section is the partial-depth variant.

Because each drawn curve has a Source, a dimension attached to a drawn line can find the model edge it measures after a rebuild, using the same history as every other operation.