D3d vertex normal

Explanation
The normal vector of a polygon is the angle pointing away from the surface.

Example
//Draw a slanted rectangle with the correct normal vector d3d_primitive_begin(pr_trianglelist); d3d_vertex_normal(-128,0,-48,  0,0.5,-0.5); d3d_vertex_normal(-128,96,48,  0,0.5,-0.5); d3d_vertex_normal(128,0,-48,  0,0.5,-0.5); d3d_vertex_normal(128,0,-48  0,0.5,-0.5); d3d_vertex_normal(-128,96,48,  0,0.5,-0.5); d3d_vertex_normal(128,96,48,  0,0.5,-0.5); d3d_primitive_end;