Lightning

GL_POSITION

If [3] != 0, x,y,z is the punctual position, and attenuation is calculated.

Otherwise, light is at infinity (like the sun, the source is a plane) and x,y,z is the incoming direction, and attenuation is ignored.

Attenuation

TODO formulas.

GL_LIGHTNING

GL_COLOR_MATERIAL

glColorMaterial

http://stackoverflow.com/questions/8494942/why-does-my-color-go-away-when-i-enable-lighting-in-opengl

https://sjbaker.org/steve/omniv/opengl_lighting.html

Summary:

without glEnable(GL_COLOR_MATERIAL), color is determined by glMaterial*
otherwise, color is determined by glColor* (like when lightning is off) sjbakr.org recommends this. We use it most of the time.