Fast GPU bounding boxes on tree-structured scenes

TL;DR

This paper introduces a fast GPU algorithm for computing bounding boxes in tree-structured scenes, significantly accelerating high-performance rendering tasks by leveraging a novel parentheses matching approach.

Contribution

It presents a new parallel GPU algorithm for bounding box computation in tree-structured scenes, based on a core parentheses matching problem, with practical implementation and performance validation.

Findings

Dramatic speedup over CPU implementation

Achieves a significant fraction of GPU theoretical throughput

Algorithm generalizes to other domains like parsing

Abstract

Computation of bounding boxes is a fundamental problem in high performance rendering, as it is an input to visibility culling and binning operations. In a scene description structured as a tree, clip nodes and blend nodes entail intersection and union of bounding boxes, respectively. These are straightforward to compute on the CPU using a sequential algorithm, but an efficient, parallel GPU algorithm is more elusive. This paper presents a fast and practical solution, with a new algorithm for the classic parentheses matching problem at its core. The core algorithm is presented abstractly (in terms of a PRAM abstraction), then with a concrete mapping to the thread, workgroup, and dispatch levels of real GPU hardware. The algorithm is implemented portably using compute shaders, and performance results show a dramatic speedup over a sequential CPU version, and indeed a reasonable fraction of maximum theoretical throughput of the GPU hardware. The immediate motivating application is 2D rendering, but the algorithms generalize to other domains, and the core parentheses matching problem has other applications including parsing.