Is there a way to achieve transparency in a specified region of the screen other than using overlay planes. I am looking for an alternative due to the rumored spotty hardware support for overlays. Any help suggestions would be greatly appreciated.
Sorry to be so vague. I am rendering 3D models over an animated 2D background and I need to be able so specify a tranparency value for a region of the screen (as opposed to transparency tied to either the individual models or backgrounds).
-render to the alpha buffer where you wish to have transparency and enable blending and us glBlendFuncSeparate(GL_ZERO,GL_ONE,GL_ONE,GL_ZERO);this copies just the alpha part of the incoming geometry to the framebuffer and leaves the rgb values untouched. of course you need GL 1.4 headers and a decent video card for top performance
-alternantively cou can render clear alpha to 0.0, render you 2d stuff and then black geometry with proper alpha and use glBlendEquation(GL_ADD); to update just the alpha channel
-when rendering the 3d models enable blending and us glBlendFunc(GL_DST_ALPHA,GL_ONE_MINUS_DST_ALPHA);
-pay attention to backfaces!
[This message has been edited by ScottManDeath (edited 12-02-2003).]