In this paper we propose two real-time models for simulating subsurface scattering for a large variety of translucent materials, which need under 0.5 milliseconds per frame to execute. This makes them a practical option for realtime production scenarios. Current state-of-the-art, real-time approaches simulate subsurface light transport by approximating the radially symmetric non-separable diffusion kernel with a sum of separable Gaussians, which requires multiple (up to twelve) 1D convolutions. In this work we relax the requirement of radial symmetry to approximate a 2D diffuse reflectance profile by a single separable kernel. We first show that low-rank approximations based on matrix factorization outperform previous approaches, but they still need several passes to get good results. To solve this, we present two different separable models: the first one yields a high-quality diffusion simulation, while the second one offers an attractive trade-off between physical accuracy and artistic control. Both allow rendering subsurface scattering using only two 1D convolutions, reducing both execution time and memory consumption, while delivering results comparable to techniques with higher cost. Using our importance-sampling and jittering strategies, only seven samples per pixel are required. Our methods can be implemented as simple post-processing steps without intrusive changes to existing rendering pipelines.



IMPORTANT: the movie, the demo and the code are not updated to the latest version of the paper, but rather corresponds to an earlier technical report. They do not feature the new artist-friendly interface, the importance sampled kernel nor the per-pixel jittering.


    author = {Jorge Jimenez and Károly Zsolnai and Adrian Jarabo and Christian Freude and Thomas Auzinger and
              Xian-Chun Wu and Javier von der Pahlen and Michael Wimmer and Diego Gutierrez},
    title = {Separable Subsurface Scattering},
    journal = {Computer Graphics Forum},
    year = {2015},
    author = {Jorge Jimenez and Veronica Sundstedt and Diego Gutierrez},
    title = {Screen-space perceptual rendering of human skin},
    journal = {ACM Transactions on Applied Perception},
    volume = {6},
    number = {4},
    year = {2009},
    pages = {23:1--23:15},
    author = {Jorge Jimenez and Diego Gutierrez},
    editor = {Wolfgang Engel},
    title = {GPU Pro: Advanced Rendering Techniques},
    chapter = {Screen-Space Subsurface Scattering},
    publisher = {{AK} Peters Ltd.},
    year = {2010},
    pages = {335--351},
    author = {Jorge Jimenez and David Whelan and Veronica Sundstedt and Diego Gutierrez},
    title = {Real-Time Realistic Skin Translucency},
    journal = {IEEE Computer Graphics and Applications},
    volume = {30},
    number = {4},
    year = {2010},
    pages = {32--41},
    author = {Jorge Jimenez and Timothy Scully and Nuno Barbosa and Craig Donner and Xenxo Alvarez and
              Teresa Vieira and Paul Matts and Verónica Orvalho and Diego Gutierrez and Tim Weyrich},
    title = {A practical appearance model for dynamic facial color},
    journal = {ACM Transactions on Graphics (Proc. SIGGRAPH Asia)},
    year = {2010},
    volume = {29},
    number = {6},
    pages = {141:1--141:10},
    author = {Jorge Jimenez and Jose I. Echevarria and Christopher Oat and Diego Gutierrez},
    editor = {Wolfgang Engel},
    title = {{GPU} Pro 2},
    chapter = {Practical and Realistic Facial Wrinkles Animation},
    publisher = {{AK} Peters Ltd.},
    year = {2011},
    author = {Jose A. Iglesias-Guitian and Carlos Aliaga and Adrian Jarabo and Diego Gutierrez},
    title = {A Biophysically-Based Model of the Optical Properties of Skin Aging},
    journal = {Computer Graphics Forum (EUROGRAPHICS 2015)},
    volume = {34},
    number = {2},
    year = {2015},