Hi Josef,
Josef Grunig wrote:
> Hi all,
>
> I've a cubeTextureChunk defined as:
>
> beginEditCP(cubetex);
> cubetex->setImage( inegz );
> cubetex->setPosZImage( iposz );
> cubetex->setPosYImage( iposy );
> cubetex->setNegYImage( inegy );
> cubetex->setPosXImage( iposx );
> cubetex->setNegXImage( inegx );
> cubetex->setMinFilter( GL_LINEAR );
> cubetex->setMagFilter( GL_NEAREST );
> cubetex->setWrapS( GL_CLAMP_TO_EDGE );
> cubetex->setWrapT( GL_CLAMP_TO_EDGE );
> cubetex->setEnvMode( GL_DECAL );
> endEditCP(cubetex);
>
> images are RGBA with ALPHA = 1;
>
> I would like to blend colors using the OpenGL Decal texture Function
> (C=Cf(1-At)+CtAt where C=RGB color, A = alpha, t = texture, f =
> fragment), but instead of using the texture's alpha I would like to
> use a custom value. A computational heavy solutions is to modify the
> whole image's alpha channel. Is there a better way for doing this?
These days the default answer to a question like is 'shader'. ;) That would
probably be the most efficient way of doing this kind of pixel math. The
problem
with shaders is having to handle all cases, which can make them a little
unwieldy.
If you don't want to or can't use shaders, the COMBINE texture environment can
probably do the same thing, by allowing you to feed constants into the blending
equation. I haven't used that in a long time, so I don't have an immediate
recipe on how to do it, but it should be possible.
Hope it helps
Dirk
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