Rendering glints on high-resolution normal-mapped specular surfaces

Abstract

our method binning reference time pixel intensity pixel normal distribution function Figure 1: A rendering of highly specular objects under point lighitng. A high-resolution normal map (2048 2 ) makes rendering impractical with standard techniques: the highlights are missed by naive pixel sampling. Left inset: Our solution is based on the concept of a pixel normal distribution function (P-NDF), which can be highly complex. Right inset: Our method is accurate even in a moving-light sequence. AbstractComplex specular surfaces under sharp point lighting show a fascinating glinty appearance, but rendering it is an unsolved problem. Using Monte Carlo pixel sampling for this purpose is impractical: the energy is concentrated in tiny highlights that take up a minuscule fraction of the pixel. We instead compute an accurate solution using a completely different deterministic approach. Our method considers the true distribution of normals on a surface patch seen through a single pixel, which can be highly complex. We show how to evaluate this distribution efficiently, assuming a Gaussian pixel footprint and Gaussian intrinsic roughness. We also take advantage of hierarchical pruning of position-normal space to rapidly find texels that might contribute to a given normal distribution evaluation. Our results show complex, temporally varying glints from materials such as bumpy plastics, brushed and scratched metals, metallic paint and ocean waves.

Discrete stochastic microfacet models

“…Most of these techniques assume very smooth normal distributions, such as Gaussians [Toksvig 2005;Olano and Baker 2010] or Gaussian mixture models [Han et al 2007]. The only normal-map rendering method capable of reproducing glittery appearance is our concurrent work [Yan et al 2014]. That method calculates accurate BRDF values for a normal map over arbitrary regions of the surface by using a hierarchical search to locate normals that are close to the half vector.…”

“…(a): when this is not the case, the correlations can lead to visible structure in reflections that our method does not simulate. In this case, the approach of Yan et al [2014] may be preferable.…”

Screen-Space Normal Distribution Function Caching for Consistent Multi-Resolution Rendering of Large Particle Data

“…Tan et al [29] approximate the overall reflectance instead of the normal distribution. Another recent approach represents NDFs for surfaces exhibiting high-frequency glints using triangulation [38].…”

A light transport model for mitigating multipath interference in Time-of-flight sensors

“…Light transport has been successfully applied to a variety of practical problems, including rendering of complex phenomena [16,49,50], imaging in poor visibility environments [17], and recovery of surface reflectance [26,35,28,27]. In addition, light transport techniques have been very successful for the challenging problem of 3-D scanning of translucent objects [25,20] and high quality structured light scanning [36,13,37,14].…”