Fast and Lazy Build of Acceleration Structures from Scene Hierarchies

In this paper we show how to use structural information about a scene such as is contained in a scene graph to build SAH-based acceleration structures more efficiently. We provide a general method for doing so together with asymptotic analyses for both standard and lazy variants of our method. In particular, we show bounds of O(n) for full k-d tree builds over n primitives and O(v + log n) for lazy k-d tree builds over v visible primitives. We provide experimental results showing that these asymptotic properties translate into real-world speedups. In fact, without a method like ours, it is impossible to achieve better than O(n) for even the first split of a lazy build. We also show that under certain (realistic) assumptions on the scene structure, our method produces provably good acceleration structures. Finally, we provide experimental results demonstrating that our acceleration structures are of nearly indistinguishable quality to those produced with a full SAH build.