The 3D Handbook
Part 1 — Foundations
Chapter

Anatomy of a mesh

Read these pages in order, or jump to the one you need.

  1. Anatomy of a polygon meshTopicWhat a polygon mesh is made of, how a game engine stores it, and why the vertex count in the engine is higher than in your modeling tool.
  2. VertexKey termA single point in 3D space; the corner of every face. In a game engine it also carries normals, UVs and colours, which is why engine vertex counts run higher.
  3. EdgeKey termA straight line between two vertices. Edges outline faces, form loops, and decide where shading and UVs break.
  4. Face (polygon)Key termThe flat area enclosed by three or more vertices; the only part of a mesh that actually renders.
  5. TriangleKey termA face with three vertices. The only polygon a GPU draws, always flat, and the unit game budgets are measured in.
  6. QuadKey termA face with four vertices. The preferred face for subdivision and deformation, and the centre of the long "all quads" debate.
  7. N-gonKey termA face with more than four vertices. Handy while modeling and harmless on flat static surfaces, but unpredictable when triangulated, subdivided or deformed.
  8. Normals (face and vertex)Key termDirections perpendicular to a surface that tell the renderer which way it faces. Face normals decide front and back; vertex normals decide how light shades across the surface.
  9. Winding order and backface cullingKey termThe order of a triangle's vertices decides which side is its front; renderers skip back faces to save work, which is why flipped faces, mirrored meshes and single-sided planes can vanish in the engine.
  10. Vertex coloursKey termA colour value stored on each vertex (or face corner) of a mesh; rarely shown as colour in games, mostly used as masks for blending materials, wear, wind and tint.
  11. Manifold and non-manifold geometryKey termA manifold mesh is a clean surface where every edge joins exactly two faces. Non-manifold geometry (extra faces on an edge, holes, loose bits, zero-area faces) confuses booleans, subdivision, 3D printing and cleanup tools.
  12. Degenerate geometryKey termFaces with no area and edges with no length, usually from stacked or collapsed vertices; invisible in the viewport but a cause of shading, baking, boolean and import problems. How to find and remove them.
  13. TriangulationKey termSplitting quads and n-gons into triangles. Every mesh is triangulated before the GPU draws it; doing it yourself, before baking, keeps shading and normal maps consistent.