Enables fogging.
Use CoglSnippet shader api for fog
Fogging causes vertices that are further away from the eye to be rendered with a different color. The color is determined according to
the chosen fog mode; at it's simplest the color is linearly interpolated so that vertices at z_near are drawn fully with
their original color and vertices at z_far are drawn fully with fog_color. Fogging will remain enabled until you
call disable_fog.
The fogging functions only work correctly when primitives use unmultiplied alpha colors. By default Cogl will premultiply textures and set_source_color will premultiply colors, so unless you explicitly load your textures requesting an unmultiplied internal format and use set_color you can only use fogging with fully opaque primitives. This might improve in the future when we can depend on fragment shaders.
| fog_color |
The color of the fog |
| mode |
A FogMode that determines the equation used to calculate the fogging blend factor. |
| density |
Used by EXPONENTIAL and by EXPONENTIAL_SQUARED equations. |
| z_near |
Position along Z axis where no fogging should be applied |
| z_far |
Position along Z axis where full fogging should be applied |