34-Issue 4

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https://diglib.eg.org/handle/10.2312/12634

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Browsing 34-Issue 4 by Subject "Ray tracing"

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    Consistent Scene Editing by Progressive Difference Images
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Günther, Tobias; Grosch, Thorsten; Jaakko Lehtinen and Derek Nowrouzezahrai
    Even though much research was dedicated to the acceleration of consistent, progressive light transport simulations, the computation of fully converged images is still very time-consuming. This is problematic, as for the practical use in production pipelines, the rapid editing of lighting effects is important. While previous approaches restart the simulation with every scene manipulation, we make use of the coherence between frames before and after a modification in order to accelerate convergence of the context that remained similar. This is especially beneficial if a scene is edited that has already been converging for a long time, because much of the previous result can be reused, e.g., sharp caustics cast or received by the unedited scene parts. In its essence, our method performs the scene modification stochastically by predicting and accounting for the difference image. In addition, we employ two heuristics to handle cases in which stochastic removal is likely to lead to strong noise. Typical scene interactions can be broken down into object adding and removal, material substitution, camera movement and light editing, which we all examine in a number of test scenes both qualitatively and quantitatively. As we focus on caustics, we chose stochastic progressive photon mapping as the underlying light transport algorithm. Further, we show preliminary results of bidirectional path tracing and vertex connection and merging.
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    Illumination-driven Mesh Reduction for Accelerating Light Transport Simulations
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Reich, Andreas; Günther, Tobias; Grosch, Thorsten; Jaakko Lehtinen and Derek Nowrouzezahrai
    Progressive light transport simulations aspire a physically-based, consistent rendering to obtain visually appealing illumination effects, depth and realism. Thereby, the handling of large scenes is a difficult problem, as in typical scene subdivision approaches the parallel processing requires frequent synchronization due to the bouncing of light throughout the scene. In practice, however, only few object parts noticeably contribute to the radiance observable in the image, whereas large areas play only a minor role. In fact, a mesh simplification of the latter can go unnoticed by the human eye. This particular importance to the visible radiance in the image calls for an output-sensitive mesh reduction that allows to render originally out-of-core scenes on a single machine without swapping of memory. Thus, in this paper, we present a preprocessing step that reduces the scene size under the constraint of radiance preservation with focus on high-frequency effects such as caustics. For this, we perform a small number of preliminary light transport simulation iterations. Thereby, we identify mesh parts that contribute significantly to the visible radiance in the scene, and which we thus preserve during mesh reduction.