Revision as of 11:44, 17 August 2014

Vertex Alpha

Each vertex in a mesh can optionally store an Alpha value, called vertex alpha. This is typically used for multitexturing or for transparency.

Because vertex alpha is simply a monochrome set of values it can be used for other purposes, like providing per-vertex sound effects in response to collisions, controlling foliage bend amount for a tree's animated vertex shader, etc.

Depending on the game engine and mesh format, a single vertex can be assigned multiple vertex alpha values. This duplicates the vertex, once for each alpha value, which allows the alpha to change suddenly from one triangle to the next, creating a hard alpha edge.

Vertices can also store VertexColor, which is typically multiplied with the DiffuseMap.