Adaptive Hierarchical Visibility in a Tiled Architecture

Abstract

This paper describes a method for occlusion culling in a tiled 3D graphics hardware architecture. Adaptive hierarchical visibility (AHV) is a simplified method for occlusion culling that is integrated into a tiled architecture for hardware rendering. AI-IV constructs a list of polygon bins for each tile where the bins are bucket sorted in order of increasing depth or Z. Polygon bins are rendered starting with the bin closest to the viewer. After some number of bins are rendered, a one layer, hierarchical Zbuffer (HZ) is constructed from the Z-buffer thus far accumulated for the rendered bins. Subsequent bins are rendered by first testing their polygons against the HZ to see if they are hidden. AHV is far simpler to implement in hardware and gives performance that matches or surpasses progressive hierarchical visibility (PHV) methods which update the HZ for each rendered pixel. Results show that AI-IV is superior on scenes with high depth complexity and small polygons. For tiles of widely ranging statistics, AHV competes surprisingly well with PHV. It offers dramatic performance improvement on low cost hardware for scenes of high depth complexity.