Rendering - Experimental Ideas & Implementations 2017

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Browsing Rendering - Experimental Ideas & Implementations 2017 by Subject "Computing methodologies"

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    Controlling and Sampling Visibility Information on the Image Plane
    (The Eurographics Association, 2017) Lessig, Christian; Matthias Zwicker and Pedro Sander
    Anti-aliasing on the image plane is a classic problems in computer graphics. While mip-mapping provides an efficient means to pre-filter texture information, no comparable technique exists for visibility. We address visibility-induced aliasing by exploiting that the Fourier transform of a discontinuity decays slowly only in the normal direction. Pre-filtering is thus only necessary in this direction and, after a coordinate transformation, the corresponding one dimensional problem can be solved analytically or tabulated. The resulting pre-filtered signal can be reconstructed exactly from pointwise samples and we derive corresponding sampling theorems that are tailored to the pre-filtering as well as a set of irregular sampling locations. We demonstrate our methodology for the classical Shannon-Nyquist setting but also for shift-invariant spaces where exact reconstruction kernels with significantly faster decay than the sinc-function are available. Our experimental results demonstrate that our pre-filtering is highly effective and that going beyond the Shannon-Nyquist setting reduces aliasing error further.
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    Temporal Coherence for Metropolis Light Transport
    (The Eurographics Association, 2017) Woestijne, Joran Van de; Frederickx, Roald; Billen, Niels; Dutré, Philip; Matthias Zwicker and Pedro Sander
    Metropolis Light Transport is a powerful global illumination algorithm, yet it has some issues that make it less suitable for animation rendering. Due to the algorithm's local exploration of path space, difficult light paths can appear very late in the rendering process or might be missing from the final image altogether. This unpredictable convergence behaviour is especially troublesome when rendering animations, since these paths need to be rediscovered for every frame. An inability to rediscover difficult light paths across the entire animation causes unpleasant flickering artefacts. Our algorithm tackles this issue by introducing temporal mutations for Metropolis Light Transport, which perturb a light path from one point in time to another, potentially across many frames. This allows us to propagate difficult paths through the entire animation. Our technique supports multiple animation types, such as camera motion and object motion, and can robustly handle different shutter setups. The convergence speed of individual frames with motion blur is increased and convergence variations between frames are diminished, especially for specular transport and difficult indirect lighting.