Collinear Faces#

Description#

Collinear faces visualization

A collinear face is a polygon whose vertices all lie nearly on a single straight line, even if the face has non-zero area. Such faces are geometrically degenerate and contribute nothing meaningful to volume definition.

Collinear faces typically result from:

  • Mesh smoothing or edge contraction algorithms

  • Importing low-quality or simplified meshes

  • Numerical precision loss during format conversion

Unlike degenerate faces (which have zero area), collinear faces may have computed non-zero area due to numerical errors, but they are still invalid for acoustic simulation.

Detection#

Detection Method: Best-fit line + perpendicular distance

Tolerance: 1e-3 m (1 mm)

Detection process:

  1. Find the two vertices with the largest pairwise distance (defines the reference line)

  2. Calculate perpendicular distance of all other vertices from this line

  3. If all vertices deviate by less than 1 mm from the line, the face is collinear

Note

This tolerance is distance-based (absolute, scale-independent). It applies regardless of model size.

Skip Condition: Faces with all vertices coincident are skipped (already caught by degenerate face detector).

Auto-Repair#

Status: ❌ No automatic repair

Action: Detection only

Collinear faces are reported but not automatically removed. This gives users the opportunity to inspect the geometry and decide on the best course of action (manual deletion, re-meshing, etc.).

Manual Fix / Avoidance#

In 3D Modelling tools (Before Export):

  1. Identify collinear faces: - Use geometry checking tools - Visualize with wireframe or face normal display - Check for faces that appear “thin” or nearly planar along one axis

  2. Remove or remesh: - Delete collinear faces manually - Make sure to check for any resulting holes or boundary edges