Directional Lights

Is there any way to create a directional light in OpenGL? This is not a point light or a spot light. A directional light has no position, and just calculates light intensity by the light direction and vertex normal. No matter where the polygon is positioned in space, a directional light will light it the same way.

How about a luminosity map? Example

Set the w component of the light position to 0 to make it a directional light. This is covered in the red book if you happen to have a copy.

Excellent. The x, y, and z components then become the directional vector.

Thanks, it works perfectly.