Zatel: Sample Complexity-Aware Scale-Model Simulation for Ray Tracing

Davit Grigoryan, Yuan-Hsi Chou, Tor M. Aamodt

Abstract: Ray tracing is a computationally intensive rendering technique that simulates the behavior of light rays as they interact with objects in a scene. It is becoming increasingly popular in video games and is already the de facto standard for animated movies. However, current hardware still struggles to efficiently ray trace complex scenes and requires further research. To evaluate early-stage hardware proposals that accelerate ray tracing for G PU s, one either uses cycle-accurate simulators, which are highly accurate and flexible but slow, or other models that are an order of magnitude faster but provide limited output with high error margins. In this paper, we propose Zatel, a prediction methodology for evaluating GPU performance on ray tracing workloads. We observe that the desired metrics can be estimated with reasonable accuracy by only tracing a representative subset of pixels. Furthermore, the parallel nature of GPUs allows us to split the scene into chunks, which lets Zatel execute faster using downscaled GPU configurations. We incorporate these two optimization steps into Zatel and evaluate it on a benchmark suite for ray tracing using Vulkan-Sim, a cycle-accurate simulator. By relying on Vulkan-Sim, architectural changes are captured through the simulator, and Zatel does not need to be updated to support each change. Zatel records less than 1 % error with 10 x simulation time speedup for measuring simulation cycles on a mobile G PU.