N-Buffers for efficient depth map query

We introduce the N-buffer as a tool for multiresolution depth map representation. This neighborhood buffer encodes the value and position of local depth extrema at different scales in an image cube, in contrast to the image pyramid. The resulting increase in storage space is largely compensated by the following benefits: objects of any size can be culled in constant time against an occlusion map using four depth lookups; visibility-like queries can be performed in vertex and fragment programs; N-buffers can be computed very efficiently with graphics hardware. We present three applications of this datastructure, and in particular a novel approach for shadow volume acceleration