Zero Area Faces#

Description#

A zero area face is a polygon that has collapsed into a point, line, or has effectively zero area. These faces cannot bound a volume and contribute nothing to the mesh topology. They are typically created by:

  • Coincident vertices (point)

  • Collinear vertices (line)

  • Self-intersecting polygons (bowties, figure-eights)

  • Numerical errors in mesh generation

Detection#

Detection Method: Newell area calculation (signed 3D normal)

Tolerance:

  • Area threshold: 1e-12 m² (area squared)

  • Altitude (sliver) threshold: 1e-4 m (0.1 mm)

A face is marked as having zero area if:

  1. Its calculated area is ≤ 1e-12 m² (effectively zero)

Why Newell? The Newell method computes a signed normal by summing cross products around the perimeter. Zero area polygons and bowties produce zero or near-zero results due to cancellation.

Auto-Repair#

Status: ✅ Automatic repair available

Repair Method: Face removal

  • All degenerate faces are deleted from the mesh

  • No mesh remeshing is performed; only the face is removed

  • Surrounding topology remains unchanged

Repair Limitations:

  • Removal can create boundary edges (edges shared by only one face) or holes in the mesh

Manual Fix / Avoidance#

In 3D Modelling Tools (Before Export):

  1. Identify sliver faces: - Use CAD tool’s geometry checking - Look for very thin or nearly flat triangles

  2. Clean up: - Delete obvious slivers manually - Use mesh smoothing or remeshing tools - Increase mesh quality/refinement settings

  3. Verify before export: - Ensure all faces have non-zero area - Check that no vertices are coincident within mesh tolerance