**Microfacet BSDFs Generated from NDFs and Explicit Microgeometry** [Mickaël Ribardière](https://mribar03.bitbucket.io)[^univP], [Benjamin Bringier](http://www.sic.sp2mi.univ-poitiers.fr/bringier)[^univP], [Lionel Simonot](https://www.researchgate.net/profile/Lionel_Simonot)[^pprim], [Daniel Meneveaux](http://d-meneveaux.blogspot.fr/)[^univP] ![Example of microfacet-based BSDFs, with very different appearances created from four configurations of Normal Distribution Functions (illustrated in insets). Microfacet properties are: Lambertian floor, perfect reflector elephant, gold conductor sphere, glass dielectric vase, and copper conductor cup. For each configuration: First row provides a rendering with multiple scattering estimated from our surface generation process; Second row provides a rendering without multiple scattering and a *CIE* $\Delta E_{00}$ color-difference image illustrating appearance changes between single and multiple scattering images](./teaser.png) [^univP]: Université de Poitiers - XLIM research institute UMR CNRS 7252 [^pprim]: Université de Poitiers - PPRIME research institute CNRS UPR 3346 Abstract ============================================ Microfacet distributions are considered nowadays as a reference for physically plausible BSDF representations. Many authors have focused on their physical and mathematical correctness, while introducing means to enlarge the range of possible appearances. This paper is dedicated to Normal Distribution Functions (NDFs), and the influence of their shape on the rendered material aspect. We provide a complete framework for studying the impact of NDFs on the observed Bidirectional Scattering Distribution Functions (BSDFs). In order to explore very general NDFs, manually controlled by the user, and including anisotropic materials, we propose to use a piecewise continuous representation. It is derived with its associated Smith shadowing-masking function and importance sampling formulations for ensuring efficient global illumination computations. A new procedure is also proposed in this paper for generating an explicit geometric micro-surface, used to evaluate the validity of analytic models and multiple scattering effects. The results are produced with a computer-generated process using path tracing. They show that this generation procedure is suitable with any NDF model, independently from its shape complexity. Publication ============================================= **Microfacet BSDFs Generated from NDFs and Explicit Microgeometry**
*M. Ribardiere, B. Bringier, L. Simonot, D. Meneveaux*
In ACM Transactions on Graphics - Volume 38, Issue 5, June 2019
[Publisher link](https://dl.acm.org/citation.cfm?id=3338697 target="_blank") Downloads ============================================= | Paper
(author's submitted version) | Additional results | Supplemental material
(Piecewise linear NDF) | Supplemental material
(SGTD NDF) | | :-----: | :------:| :------:| :------:| | [](paper_low.pdf)
4.8 MB pdf | [](additional.pdf)
45 MB pdf | [](supplemental_piecewise.pdf)
596KB pdf | [](supplemental_SGTD.pdf)
529KB pdf | Code ============================================= [Source code page.](https://dl.acm.org/citation.cfm?id=3338697 target="_blank")