NV_Occlusion_Query Example

I have coded a small postprocessor used to display results of fluid dynamics simulations. It is using an octree decomposition on which I perform frustum culling and also occlusion culling using the HP_occlusion extension. As anybody noticed, this is a rather slow option and my not so accurate occlusion mapping implementation (Zhang paper) is faster but does not cull as much as the HP_Occlusion test. I have noticed the Nvidia extension which is supposed to alleviate the speed problem by being performed in parallel to any CPU computation. Unfortunately, I do not have much to do between the queries. It is done as follows: * Look at a cell within the octree. 1) If the cell contains sets of triangles, perform the occlusion test if they are large sets and display accordingly. 2)if this a branch, test the 8 subcells for occlusion (using bounding box). 2) retrieve the number of pixels displayed and decide to go down one level or not I am only checking every frames for the visible sets and every other frames (5 frames) for the previously hidden sets to reduce the number of test. As anyone an idea on how to implement cleverly the NV extension in such configuration. Thanks for any feedback Eric