This function will add surface normal data to the vertex currently being defined for the custom primitive. You supply the buffer to write the data into as well as the x, y and z component parts of the normal.
vertex_normal(buffer, nx, ny, nz);
|buffer||The buffer to write the information to.|
|nx||The x component of the surface normal.|
|ny||The y component of the surface normal.|
|nz||The z component of the surface normal.|
vertex_normal(buff, 0, 1, 1);
The above code will set the surface normal of the vertex being defined.