   question to occlusion culling
  Hello,at the moment my volume rendering is without any performance improvements.So I want to use an octree. The knots hold information about the alpha value. If its zero then this knot is not visible and the texcoordsof the vertices of this non-visible knot wont be send to the shader. But there is one problem. There will be sub-boxes in the octree that are visible but theyare occluded by visible boxes infront of them. At this time, the vertices ofall visible boxes will be send to the shader. So I need a way to find outwhat are the front boxes and what boxes are occluded.Somewhere I read that the octree has to be sorted front to back each time theview direction changes. But I dont understand why to sort front to back.When I've created the octree and sampled the knots with the transfer functioni set each sub-box to visible or non-visible. They have their position.And when I sort front to back, that would mix it al up. And parts will be rendered that are not visible and visible parts will be not rendered.regards,c-mos   
  I think what you heard about are BSP trees, which are not the same thing. They draw the scene back to front. Why send the alpha value to the shader, when it`s easier and a lot faster to simply not draw the content of those boxes.Octrees are used for frustrum culling, not for occlusion culling. You would have to use a more sophisticated algorithm for that:)   ;  It is used for volume rendering (gpu raycasting). So the volume is divided into smaller sub volumes. They have to be sorted in a front to back manner. the alpha value decides wether the sob volume will be raycasted or not. I dont understand why to sort the octree.regards,c-mos   