Xavier Chermain, Frédéric Claux and Stéphane Mérillou

EGSR 2019, CGF Track

Our 2019 EGSR, CGF Track, paper

Abstract

Rendering materials such as metallic paints, scratched metals and rough plastics requires glint integrators that can capture all micro-specular highlights falling into a pixel footprint, faithfully replicating surface appearance. Specular normal maps can be used to represent a wide range of arbitrary micro-structures. The use of normal maps comes with important drawbacks though: the appearance is dark overall due to back-facing normals and importance sampling is suboptimal, especially when the micro-surface is very rough. We propose a new glint integrator for specular surfaces relying on a multiple-scattering patch-based BRDF addressing these issues. To do so, our method uses a modified version of microfacet-based normal mapping [Schüssler et al. 2017] designed for glint rendering, leveraging symmetric microfacets. To model multiple-scattering, we re-introduce the lost energy caused by a perfectly specular, single-scattering formulation instead of using expensive random walks. This reflectance model is the basis of our patch-based BRDF, enabling robust sampling and artifact-free rendering with a natural appearance. Additional calculation costs amount to about 40% in the worst cases compared to previous methods [Yan et al. 2016, Chermain et al. 2018].

Post-peer-review, pre-copyedit version

Post-peer-review, pre-copyedit version file

Video

Video file

Code

code