Real-Time Occlusion Culling with a Lazy Occlusion Grid

Abstract

We present a new conservative image-space occlusion culling method to increase the rendering speed of very large general scenes on today's available hardware without time-expensive preprocessing. The method is based on a low-resolution grid upon a conventional z-buffer. The occlusion information in the grid is updated in a lazy manner. In comparison to related methods this significantly reduces the number of pixels that have to be read from the z-buffer. The grid allows fast decisions if an object is occluded or potentially visible. It is used together with a bounding volume hierarchy that is traversed in a front-to-back order and which allows to cull large parts of the scene at once. A special front-to-back traversal is used if no pixel-level query for the furthest z-value of an image area is available. We show that the method works efficiently on today's available hardware and we compare it with related methods.