A nuclear can ruin your whole day

Concept 3.3 : Diffuse Lighting
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Idea:
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The diffuse componenet is the light that comes
from one direction, so its brighter if it comes
squarely down on a surface than if it barely 
glances off the surface.  Once it hits the surface
however, it's scattered equally in all directions.
Use:
GLfloat light_diffuse[] = {R, G, B, A};
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
to set the diffuse component of light0.