The light will create
a new light or rewrite the existing light on this index. The specular light is directed
light by the vector of sun. And the light of textures is a calculated by pixel.
The color of pixel is calculated for his texture by a non linear formula, but the
textures is black (rgb 0,0,0) then
the color could not be non linear on this texture.
index: All lights are assigned to a index.
background: the basic color of this light
lightcolor: the reflection color of this light