Research

Filtering Distributions of Normals for Shading Antialiasing

"Filtering Distributions of Normals for Shading Antialiasing"
Anton Kaplanyan (NVIDIA), Stephen Hill (Ubisoft Montreal), Anjul Patney (NVIDIA), Aaron Lefohn (NVIDIA), in High-Performance Graphics (best paper), June 2016
Research Area: 3D Graphics
Author(s): Anton Kaplanyan (NVIDIA), Stephen Hill (Ubisoft Montreal), Anjul Patney (NVIDIA), Aaron Lefohn (NVIDIA)
Date: June 2016
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Abstract: High-frequency illumination effects, such as highly glossy highlights on curved surfaces, are challenging to render in a stable manner. Such features can be much smaller than the area of a pixel and carry a high amount of energy due to high reflectance. These highlights are challenging to render in both offline rendering, where they require many samples and an outliers filter, and in real-time graphics, where they cause a significant amount of aliasing given the small budget of shading samples per pixel. In this paper, we propose a method for filtering the main source of highly glossy highlights in microfacet materials: the Normal Distribution Function (NDF). We provide a practical solution applicable for real-time rendering by employing recent advances in light transport for estimating the filtering region from various effects (such as pixel footprint) directly in the parallel-plane half-vector domain (also known as the slope domain), followed by filtering the NDF over this region. Our real-time method is GPU-friendly, temporally stable, and compatible with deferred shading, normal maps, as well as with filtering methods for normal maps.