Differentiable Monte Carlo Ray Tracing Through Edge Sampling

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2018
Major/Subject
Mcode
Degree programme
Language
en
Pages
1-11
Series
ACM Transactions on Graphics, Volume 37, issue 6
Abstract
Gradient-based methods are becoming increasingly important for computer graphics, machine learning, and computer vision. The ability to compute gradients is crucial to optimization, inverse problems, and deep learning. In rendering, the gradient is required with respect to variables such as camera parameters, light sources, scene geometry, or material appearance. However, computing the gradient of rendering is challenging because the rendering integral includes visibility terms that are not differentiable. Previous work on differentiable rendering has focused on approximate solutions. They often do not handle secondary effects such as shadows or global illumination, or they do not provide the gradient with respect to variables other than pixel coordinates. We introduce a general-purpose differentiable ray tracer, which, to our knowledge, is the first comprehensive solution that is able to compute derivatives of scalar functions over a rendered image with respect to arbitrary scene parameters such as camerapose, scene geometry, materials, and lighting parameters. The key to our method is a novel edge sampling algorithm that directly samples the Dirac delta functions introduced by the derivatives of the discontinuous integrand. We also develop efficient importance sampling methods based on spatial hierarchies. Our method can generate gradients in times running from seconds to minutes depending on scene complexity and desired precision. We interface our differentiable ray tracer with the deep learning library PyTorch and show prototype applications in inverse rendering and the generation of adversarial examples for neural networks.
Description
Keywords
computer graphics, inverse rendering, ray tracing
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Citation
Li , T-M , Aittala , M , Durand , F & Lehtinen , J 2018 , ' Differentiable Monte Carlo Ray Tracing Through Edge Sampling ' , ACM Transactions on Graphics , vol. 37 , no. 6 , 222 , pp. 1-11 . https://doi.org/10.1145/3272127.3275109