Glossary

-C-

Coincident

Coincident vertices share the same coordinate space, but are incident to two separate edges.

-D-

Degenerate triangles

A degenerate triangle does not have any area.

-I-

Incident

When an edge connects two vertices, those vertices are both incident to the edge.

-M-

Manifold and non-manifold geometry

Manifold geometry is well-formed and could exist in the real world. Non-manifold geometry can cause errors and could de-stabilize your project. The following are examples of non-manifold geometry:

• Inner faces (faces enclosed inside another set of faces)
• Overlapping faces (occupying the same space)
• Faces that bisect another mesh
• Self-intersecting faces

-Q-

Quad (quadrangle)

Most polygons are "triangulated", or divided into faces with three edges. However, ProBuilder supports four-sided faces, or "quadrangles" in many cases. "Quad" is the abbreviation for "quadrangle".

-W-

Winding order

Winding order determines how a polygon's vertices are rendered (clockwise vs. counter-clockwise). A clockwise winding order is sometimes called "right-handed" and a counter-clockwise winding order is sometimes called "left-handed". In left-handed coordinate systems like Unity, where the y-axis is "up", counter-clockwise winding is front-facing. For right-handed systems, the rendering order is opposite .

Winged edge

When three or more faces meet at a boundary, the vertex where they meet is coincident with multiple faces and edges. The WingedEdge is a structure that holds information about a face, an edge, and a vertex at that boundary. It also provides a list of coincident edges so you can use the EdgeLookup to access information about them through scripting.