Offscreen transparency on ATI and Nvidia cards

Hi guys!

Im using the sraight forward, easy way to render to offscreen by render to the back buffer and grab the result using the glCopyTexImage2D command.
( Think I found it in a tutorial at NeHe production. )
If I use the GL_RGB image format, I get a solid image, and by using the GL_RGBA format I get an image with the clear color transparent.
Like this:

This works 120% on my ATI Radeon X850. BUT, when I run the program on ANY Nvidia chipset, no matter if its new or old, the texture is NOT transparent anymore!!

Is this a manufacturer issue or should I use another technique to get it transparent??
Im using shaders and stuff so I surely could find another way around but Im quite curious if any one else had this problem.

Thanx in advance!!

make sure that you have declared to want an alpha channel in your pixel format. If you left the alpha bits unspecified, it is probable that NVidia gives you a RGB back buffer and ATI a RGBA back buffer…


Yep, of course that was the problem!!

Thank you!! :stuck_out_tongue:

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