61 lines
2.0 KiB
Markdown
61 lines
2.0 KiB
Markdown
# Glossary
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## -C-
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<a name="coincident"></a>
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### Coincident
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_Coincident_ vertices share the same coordinate space, but are [incident](#incident) to two separate edges.
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## -D-
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<a name="degenerate"></a>
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### Degenerate triangles
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A degenerate triangle does not have any area.
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## -I-
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<a name="incident"></a>
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### Incident
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When an edge connects two vertices, those vertices are both _incident_ to the edge.
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## -M-
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<a name="manifold"></a>
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### Manifold and non-manifold geometry
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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:
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* Inner faces (faces enclosed inside another set of faces)
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* Overlapping faces (occupying the same space)
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* Faces that bisect another mesh
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* Self-intersecting faces
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## -Q-
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<a name="quad"></a>
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### Quad (quadrangle)
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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".
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## -W-
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<a name="winding"></a>
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### Winding order
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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 .
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<a name="winged-edge"></a>
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### Winged edge
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When three or more faces meet at a boundary, the vertex where they meet is _coincident_ with multiple faces and edges. The [WingedEdge](xref:UnityEngine.ProBuilder.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](xref:UnityEngine.ProBuilder.EdgeLookup) to access information about them through scripting.
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