Physically based shading in theory and practice

Hill, Stephen; Rayani, Farhez; Rousiers, Charles de; McAuley, Stephen; Dupuy, Jonathan; Gotanda, Yoshiharu; Heitz, Eric; Hoffman, Naty; Lagarde, Sébastien; Langlands, Anders; Megibben, Ian

doi:10.1145/2614028.2615431

Cited by 21 publications

(16 citation statements)

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“…for interactive rendering [WKB*02, SIMP06] or factorized axis‐aligned filtering [MYRD14]. A fundamental problem of this approach is that it builds upon a linear shading model, which is invalidated by most realistic shading models [HMD*14], spatial anti‐aliasing, and distribution effects such as depth‐of‐field or motion blur. We propose a generalized lighting–texture factorization that does not suffer from this problem; we demonstrate its effectiveness on depth‐of‐field and state‐of‐the‐art microfacet reflectance models.…”

Section: Related Workmentioning

confidence: 99%

Path‐space Motion Estimation and Decomposition for Robust Animation Filtering

Zimmer

Rousselle

Jakob

et al. 2015

Computer Graphics Forum

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Renderings of animation sequences with physics‐based Monte Carlo light transport simulations are exceedingly costly to generate frame‐by‐frame, yet much of this computation is highly redundant due to the strong coherence in space, time and among samples. A promising approach pursued in prior work entails subsampling the sequence in space, time, and number of samples, followed by image‐based spatio‐temporal upsampling and denoising. These methods can provide significant performance gains, though major issues remain: firstly, in a multiple scattering simulation, the final pixel color is the composite of many different light transport phenomena, and this conflicting information causes artifacts in image‐based methods. Secondly, motion vectors are needed to establish correspondence between the pixels in different frames, but it is unclear how to obtain them for most kinds of light paths (e.g. an object seen through a curved glass panel). To reduce these ambiguities, we propose a general decomposition framework, where the final pixel color is separated into components corresponding to disjoint subsets of the space of light paths. Each component is accompanied by motion vectors and other auxiliary features such as reflectance and surface normals. The motion vectors of specular paths are computed using a temporal extension of manifold exploration and the remaining components use a specialized variant of optical flow. Our experiments show that this decomposition leads to significant improvements in three image‐based applications: denoising, spatial upsampling, and temporal interpolation.

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Section: Related Workmentioning

confidence: 99%

Path‐space Motion Estimation and Decomposition for Robust Animation Filtering

Zimmer

Rousselle

Jakob

et al. 2015

Computer Graphics Forum

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“…Also, storing high quality normals requires additional bandwidth; more traditional ways of encoding the normal in 8‐bit or 16‐bit variables would lead to severe artifacts caused by the highly specular phenomenon that we are modeling. The shading pipeline used by our Tenderer follows the widely adopted principles within production real‐time Tenderers [HMD*14].…”

Section: Methodsmentioning

confidence: 99%

Real‐Time Rendering of Wave‐Optical Effects on Scratched Surfaces

Velinov

Werner

Hullin

2018

Computer Graphics Forum

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The visual appearance of real‐world materials is characterized by surface features across many scales and has received significant attention by the graphics community for decades. Yet, even the most advanced microfacet models have difficulties faithfully recreating materials like snow, sand, brushed metal or hair that feature scale‐violating glints and speckles and defy any traditional notion of filtering and level of detail. In this work, we address an important subset of such materials, namely metal and dielectric surfaces that are covered with microscopic scratches, e.g., from polishing processes or surface wear. The appearance of such surfaces features fine‐scale spatial detail and iridescent colors caused by diffraction, and has only recently been successfully recreated. We adopt the scratch iridescence model, which is known for plausible results in offline Monte Carlo settings but unsuitable for real‐time applications where extensive illumination sampling is prohibitively expensive. In this paper, we introduce an efficient technique for incoherently integrating the contributions of individual scratches, as well as closed‐form solutions for modeling spherical and polygonal area light sources, and for the first time bring scratch iridescence within reach of real‐time applications.

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“…10). Later, the same distribution was independently proposed by Walter et al [2007] and named GGX; it is nowadays widely used in microfacet BRDFs [Hill et al 2014]. However, the GGX distribution uses only the upper part of the ellipsoid according to a local frame and does not allow for filtering or interpolation when the different input distributions are not defined in the same frame.…”

Section: The Ggx Distributionmentioning

confidence: 99%

The SGGX microflake distribution

Heitz

Dupuy

Crassin³

et al. 2015

ACM Trans. Graph.

Self Cite

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Figure 1: Top-left: rendering a voxelized forest at decreasing levels of detail (left to right). Bottom-right: visualization of the voxel structure at the matching resolutions. We use the SGGX microflake distribution to represent volumetric anisotropic materials. Our representation supports downscaling and interpolation, resulting in smooth and antialiased renderings at multiple scales. AbstractWe introduce the Symmetric GGX (SGGX) distribution to represent spatially-varying properties of anisotropic microflake participating media. Our key theoretical insight is to represent a microflake distribution by the projected area of the microflakes. We use the projected area to parameterize the shape of an ellipsoid, from which we recover a distribution of normals. The representation based on the projected area allows for robust linear interpolation and prefiltering, and thanks to its geometric interpretation, we derive closed form expressions for all operations used in the microflake framework.We also incorporate microflakes with diffuse reflectance in our theoretical framework. This allows us to model the appearance of rough diffuse materials in addition to rough specular materials. Finally, we use the idea of sampling the distribution of visible normals to design a perfect importance sampling technique for our SGGX microflake phase functions. It is analytic, deterministic, simple to implement, and one order of magnitude faster than previous work.

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Physically based shading in theory and practice

Cited by 21 publications

References 0 publications

Path‐space Motion Estimation and Decomposition for Robust Animation Filtering

Path‐space Motion Estimation and Decomposition for Robust Animation Filtering

Real‐Time Rendering of Wave‐Optical Effects on Scratched Surfaces

The SGGX microflake distribution

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