Buffering

Stage 5 of five. Operates on hexahedra. See Hexahedral Meshing from a Surface for the pipeline overview and terminology.

Trimming leaves a blocky, stair-stepped boundary that does not follow the surface. Buffering resolves this by adding one conforming layer:

1. The exterior faces of the trimmed mesh are extracted.
2. Each boundary node is projected to its closest point on the surface.
3. A hexahedron is extruded from each boundary face out to the projected nodes.

Before projecting, the extracted boundary is checked for manifoldness: every edge must be shared by exactly two faces. If not, meshing fails with

Error: non-manifold boundary.

This check is on the output boundary, not the input surface, and it is the only manifoldness test in the pipeline. It is a common failure — see Failure Modes.

The buffer elements are the only elements whose geometry is fitted to the surface, and consequently the only elements whose quality is unbounded. A poorly resolved or highly curved surface region will show up here and nowhere else.

Previous: Trimming. This is the final stage; the mesh is written out from here. For what to do with the result, see Quality Assessment and Improvement.