Journal of Computer Graphics Techniques

Computer Company

Philippe Weier and Laurent Belcour, Rendering Layered Materials with Anisotropic Interfaces, Journal of Computer Graphics Techniques (JCGT), vol. 9, no. 2, 37-57, 2020
Available online http://jcgt.org/published/0009/02/03/

We present a lightweight and efficient method to render layered materials with anisotropic interfaces. Our work extends the statistical framework of Belcour [2018] to handle anisotropic microfacet models. A key insight to our work is that when projected on ...the tangent plane, BRDF lobes from an anisotropic GGX distribution are well approximated by ellipsoidal distributions aligned with the tangent frame: its covariance matrix is diagonal in this space. We leverage this property and perform the adding-doubling algorithm on each anisotropy axis independently. We further update the mapping of roughness to directional variance and the evaluation of the average reflectance to account for anisotropy. We extensively tested this model against ground truth.

Theodore Kim and Tom Duff, A Massive Fractal in Days, Not Years, Journal of Computer Graphics Techniques (JCGT), vol. 9, no. 2, 26-36, 2020
Available online http://jcgt.org/published/0009/02/02/

We present a new, numerically stable algorithm that allows us to compute a previously-infeasible, fractalized Stanford Bunny composed of 10 billion triangles. Recent work [Kim 2015] showed that it is feasible to compute quaternion Julia sets that conform to any arbitrary shape. Howeve...r, the scalability of the technique was limited because it used high-order rationals requiring 80 bits of precision. We address the sources of numerical difficulty and allow the same computation to be performed using 64 bits. Crucially, this enables computation on the GPU, and computing a 10-billion-triangle model now takes 17 days instead of 10 years. We show that the resulting mesh is useful as a test case for a distributed renderer.