   Hardware Occlusion Queries - openGL 2.0
  Hi,I am interested in using the NV occlusion query calls to determine visibility in indoor scenes.  After rendering every wall, I want to do something like the following:Gluint queries[N];GLuint pixelCount;glGenOcclusionQueriesNV(N, queries);for (i=0; i<N; i++) {   glBeginOcclusionQueryNV(queries); // render bounding box for i'th geometry   glEndOcclusionQueryNV();   }for (i=0; i<N; i++) {   glGetOcclusionQueryuivNV(queries, GL_PIXEL_COUNT_NV, &pixelCount);   if (pixelCount > MAX_COUNT)  // render geometry   }http://developer.nvidia.com/object/gdc_occlusion.html The link above is to a presentation given by Ashu Rege at GDC 2002.  My question is this:  Is there an updated way to achieve this result without using the NV extensions?  Does this work on ATI cards?  Should these same function calls be used on an openGL 2.0 card?Thanks.   
  GL_NV_occlusion_query apparently does work on ATI cards, but I recommend using the ARB version, GL_ARB_occlusion_query.  There are some differences between the NV and ARB versions.   