OpenGL Programming Guide

Appendix AOrder of Operations

Geometric Operations

Per-Vertex Operations

In the per-vertex operations stage of processing, each vertex's spatial coordinates are transformed by the modelview matrix, while the normal vector is transformed by that matrix's inverse and renormalized if specified. If automatic texture generation is enabled, new texture coordinates are generated from the transformed vertex coordinates, and they replace the vertex's old texture coordinates. The texture coordinates are then transformed by the current texture matrix and passed on to the primitive assembly step.

Meanwhile, the lighting calculations, if enabled, are performed using the transformed vertex and normal vector coordinates, and the current material, lights, and lighting model. These calculations generate new colors or indices that are clamped or masked to the appropriate range and passed on to the primitive assembly step.

OpenGL Programming Guide