View Full Version : GL_MODULATE internal working

02-25-2002, 08:39 AM
I wish to know what algorithm OpenGL uses while putting a texture in GL_MODULATE mode especially how the texture color is modulated w.r.t pixel Color.
Also details about GL_BLEND are also welcome


02-25-2002, 08:48 AM
Modulate = texture color * previous color
Blend = alpha * texture color + (1 - alpha) * primary color

Information about stuff like this can easily be found in the specs, so there isn't really a need to ask.


02-25-2002, 08:53 AM
The specifications for OpenGL 1.3 are found on this web site, in the documentation section. Get the PDF file; it even has an index in the back which makes finding things a snap. Note that there are some things the specification doesn't guarantee, such as number of bits used in internal calculation, color component rounding of intermediate results, etc.

02-26-2002, 07:49 AM
Thanks J and jwatte
Well, the formulae really sum up the essence of the algo for modulate and blending. The specific info on pixels I was looking for was there in the specification after I rescanned it on ur suggestion.