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Michbeck

Portals

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I have a question: Is there any way to tell if a polygon which is chucked at the rasterizer affects the depth buffer or color buffer? I mean is there any way to see whether the polygon i just gave to the graphics hardware is clipped away either because it''s not in the view frustum or because it''s completely behind the z-buffer contents? I think it should be very easy for the hardware to track that: Just manually clear a flag at the beginning, and whenever the graphics card actually sets a pixel, it sets the flag. Easy as that. If you could do that, then it would be very cool for a portal engine, you could draw all the current sector''s polygons first. Then the portals and each time check whether it affected the buffers. If yes, draw the sector on the other side... and so on. I know that normally I just would have to perform frustum culling on the portal polygons myself... just wanted to know whether that is possible. Thank you.

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Weeee I found out for myself!

for everyone who cares:

there a GL_HP_occlusion_test and based on it, a GL_NV_occlusion_query extension.

:]

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