This function will set the texture coordinates to use for the vertex currently being defined for the custom primitive. You supply the buffer to write the data into as well as the UV position within the texture to use.
vertex_texcoord(buffer, u, v);
|buffer||The buffer to write the information to.|
|u||The first texture coordinate to use (0 - 1).|
|v||The second texture coordinate to use (0 - 1).|
vertex_texcoord(buff, 0, 0);
The above code will set the UV values of the vertex being defined.