Rendering - Experimental Ideas & Implementations 2015

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https://diglib.eg.org/handle/10.2312/12636

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    High Performance Non-linear Motion Blur
    (The Eurographics Association, 2015) Guertin, Jean-Philippe; Nowrouzezahrai, Derek; Jaakko Lehtinen and Derek Nowrouzezahrai
    Motion blur is becoming more common in interactive applications such as games and previsualization tools. Here, a common strategy is to approximate motion blur with an image-space post-process, and many recent approaches demonstrate very efficient and high-quality results [Sou13,GMN14]. Unfortunately, all such approaches assume underlying linear motion, and so they cannot approximate non-linear motion blur effects without significant visual artifacts.We present a new motion blur post-process that correctly treats the case of non-linear motion (in addition to linear motion) using an efficient curve-sampling scatter approach. We simulate plausible non-linear motion blur in 4ms at 1920 1080 and our approach has many desirable properties: its cost is independent of geometric complexity, it robustly estimates blurring extents to avoid typical over- and under-blurring artifacts, it supports unlimited motion magnitudes, and it is less noisy than existing techniques.
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    Practical Rendering of Thin Layered Materials with Extended Microfacet Normal Distributions
    (The Eurographics Association, 2015) Guo, Jie; Qian, Jinghui; Pan, Jingui; Jaakko Lehtinen and Derek Nowrouzezahrai
    We propose a practical reflectance model for rendering thin transparent layers with different sides varying in roughness and levels of gloss. To capture the effect of subsurface reflection, previous methods rely on importance sampling for each light-surface interaction. This soon becomes a computationally demanding task since a recursive sampling scheme is required to handle multiple internal reflections. In this paper, we first provide a comprehensive analysis of the relationship between the directional distribution of scattered light and the roughness of each layer boundary using joint spherical warping. Based on the analysis, we generalize the traditional microfacet theory for layered materials and introduce the extended normal distribution function (ENDF) to accurately model the behavior of subsurface reflection. With the ENDF, the number of sampling processes can be reduced to only once for each bounce of subsurface reflection. We demonstrate that our BSDF model based on the ENDF is easy to be implemented on top of Monte Carlo sampling based offline renderers and it incurs little computational overhead. Moreover, it can be also efficiently used in real-time applications with the help of GPU acceleration.