photoshop blending mode


I think it would be a great idee to add the way to use photoshop blending mode … they are more and more popular … or perhaps a blending programmable pipeline… It seems to be a very usefull things…
any comments ?


Photoshop blending mode, no, it would be to complicated to implement.
Besides you can already implement most of it save for a few of them using glBlendFunc and glBlendEquation

programmable blending pipeline stage, yes please.

with glBlendFunc and glBlendEquation you can only implement a small number of photoshop mode… at the moment it seems that the only way to implement it is to use FBO to read the framebuffer and a pixel shader to blend the incoming fragment with the framebuffer… trolltech use this way for example to add more blending mode … (you can see that at……)
but it’s quite a lot of overhead just for a simple things !!! just add the needed glblendfunc to support all the common mode !!

elezaza - this is a hardware-feature so don’t expect it to be added to OpenGL until hardware supports it.

The FBO-way does add overhead, but for a lot of applications utilizing strange blendmodes you would want to do it this way anyway.