How to Render the Shadow
/* Render 50% black shadow color on top of whatever
the floor appearance is. */
glBlendFunc(GL_SRC_ALPHA,
glDisable(GL_LIGHTING); /* Force the 50% black. */
glColor4f(0.0, 0.0, 0.0, 0.5);
/* Project the shadow. */
glMultMatrixf((GLfloat *) floorShadow);