Rendering - Experimental Ideas & Implementations 2016

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https://diglib.eg.org/handle/10.2312/15442

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Browsing Rendering - Experimental Ideas & Implementations 2016 by Subject "shading"

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    4D-rasterization for Fast Soft Shadow Rendering
    (The Eurographics Association, 2016) Wang, Lili; Zhao, Qi; Meng, Chunlei; Popescu, Voicu; Elmar Eisemann and Eugene Fiume
    This paper describes an algorithm for rendering soft shadows efficiently by generalizing conventional triangle projection and rasterization from 2D to 4D. The rectangular area light source is modeled with a point light source that translates with two degrees of freedom. This generalizes the projection of triangles and of output image samples, as seen from the light, to the locus of projections as the light translates. The generalized projections are rasterized to determine a conservative set of sample/ triangle pairs, which are then examined to derive light occlusion masks for each sample. The algorithm is exact in the sense that each element of the occlusion mask of a sample is computed accurately by considering all potentially blocking triangles. The algorithm does not require any type of precomputation so it supports fully dynamic scenes. We have tested our algorithm on several scenes to render complex soft shadows accurately at interactive rates.
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    Deep Partitioned Shadow Volumes Using Stackless and Hybrid Traversals
    (The Eurographics Association, 2016) Mora, Frédéric; Gerhards, Julien; Aveneau, Lilian; Ghazanfarpour, Djamchid; Elmar Eisemann and Eugene Fiume
    Computing accurate hard shadows is a difficult problem in interactive rendering. Previous methods rely either on Shadow Maps or Shadow Volumes. Recently Partitioned Shadow Volumes (PSV) has been introduced. It revisits the old Shadow Volumes Binary Tree Space Partitioning algorithm, leading to a practicable and efficient technique. In this article, we analyze the PSV query algorithm and identify two main drawbacks: First, it uses a stack which is not GPU friendly; its size must be small enough to reduce the register pressure, but large enough to avoid stack overflow. Second, PSV struggles with configurations involving significant depth complexity, especially for lit points. We solve these problems by adding a depth information to the PSV data structure, and by designing a stackless query. In addition, we show how to combine the former PSV query with our stackless solution, leading to a hybrid technique taking advantage of both. This eliminates any risk of stack overflow, and our experiments demonstrate that these improvements accelerate the rendering time up to a factor of 3.
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    Fast Shadow Map Rendering for Many-Lights Settings
    (The Eurographics Association, 2016) Selgrad, Kai; Müller, Jonas; Reintges, Christian; Stamminger, Marc; Elmar Eisemann and Eugene Fiume
    In this paper we present a method to efficiently cull large parts of a scene prior to shadow map computations for many-lights settings. Our method is agnostic to how the light sources are generated and thus works with any method of light distribution. Our approach is based on previous work in culling for ray traversal to speed up area light sampling. Applied to shadow mapping our method works for high- and low-resolution shadow maps and, in contrast to previous work on many-lights rendering, does neither entail scene approximations nor imposes limits on light range, while still providing significant gains in performance. In contrast to standard culling methods shadow map rendering itself is sped up by a factor of 1.5 to 8.6 while the speedup of shadow map rendering, lookup and shading together ranges from 1.1 to 4.2.
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    A General Micro-flake Model for Predicting the Appearance of Car Paint
    (The Eurographics Association, 2016) Ergun, Serkan; Önel, Sermet; Ozturk, Aydin; Elmar Eisemann and Eugene Fiume
    We present an approximate model for predicting the appearance of car paint from its paint composition. Representing the appearance of car paint is not trivial because of its layered structure which is composed of anisotropic scattering media. The Radiative Transfer Equation (RTE) is commonly used to represent the multiple scattering for the underlying structures. A number of techniques including the Monte Carlo approach, the discrete ordinates, the adding-doubling method, the Eddington approximation, as well as the 2-stream and diffusion approximations have been proposed so far to improve visualization accuracy. Each of these techniques hold advantages over the others when their appropriate conditions are met. The adding-doubling method, in particular, is recognized to be computationally simple and accurate. Jakob et al. [JAM 10] has generalized the RTE for anisotropic scattering structures and proposed to use a micro-flake model based on double-sided specularly reflecting flakes. They also developed an anisotropic diffusion approximation to solve the corresponding RTE. In this paper, considering the translucent micro-flakes we proposed to use a modified version of the model which was developed by Jakob et al. We utilized the adding-doubling method instead of the diffusion-approximation for the new micro-flake model. The proposed approach also provided a good ground for data compression used in the evaluation of RTE. Empirical comparisons have been made to assess the accuracy and computational efficiency of the proposed model. Based on the sample data, we showed that our model provides visually satisfactory results for the appearance of multi-layered car paint.
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    Shape Depiction for Transparent Objects with Bucketed k-Buffer
    (The Eurographics Association, 2016) Murray, David; Baril, Jerome; Granier, Xavier; Elmar Eisemann and Eugene Fiume
    Shading techniques are useful to deliver a better understanding of object shapes. When transparent objects are involved, depicting the shape characteristics of each surface is even more relevant. In this paper, we propose a method for rendering transparent scenes or objects using classical tools for shape depiction in real time. Our method provides an efficient way to compute screen space curvature on transparent objects by using a novel screen space representation of a scene derived from Order Independent Transparency techniques. Moreover, we propose a customizable stylization that modulates the transparency per fragment, according to its curvature and its depth, which can be adapted for various kinds of applications.