Blending operation with frame buffer

[Arath]

Hi,

I work on commercial project using (of course unfortunately) DirectX (there is only "that" on the XBOX), but I am a huge
fan of OpenGL (as you may have guessed) and my home engine is written with this API. I just can't find in the OpenGL API
a function very usefull which exists in DirectX : the blending operation. I'm not talking about the blending sources (I mean glBlendfunc)
, it seems like in openGL the blending equation is fixed (result = fragment * sfactor + framebuffer * dfactor) and not in D3D (very weird?). With
this renderstate D3DBLENDOP we can substract or add (usefull to do substractive blending). Is there a similar function/renderstate in OpenGL?

Cheers
Arath

[Asgard]

Yes, OpenGL is capabable of doing all that. Look at the EXT_blend_subtract, EXT_blend_minmax, EXT_blend_func_separate, and EXT_blend_color extensions, which I believe are all part of core OpenGL 1.4 now.

[roffe]

http://wwws.sun.com/software/graphic...uationEXT.html

[Arath]

Thanks a lot,
eventually my faith in opengl is not gone ;-)

Arath

[V-man]

Hey, that is sweet. I didn't know that sun had such nice looking man pages.

I've spent all this time reading crappy ASCII text.