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ABSTRACT: The interaction of light and matter in the world surrounding us is of striking complexity and beauty. Since the very beginning of computer graphics, adequate modelling of these processes and efficient computation is an intensively studied research topic and still not a solved problem. The inherent complexity stems from the underlying physical processes as well as the global nature of the interactions that let light travel within a scene. This paper reviews the state of the art in interactive global illumination (GI) computation, i.e., methods that generate an image of a virtual scene in less than 1 s with an as exact as possible, or plausible, solution to the light transport. Additionally, the theoretical background and attempts to classify the broad field of methods are described. The strengths and weaknesses of different approaches, when applied to the different visual phenomena, arising from light interaction are compared and discussed. Finally, the paper concludes by highlighting design patterns for interactive GI and a list of open problems.
Computer Graphics Forum 01/2012; 31(1):160 - 188. · 1.63 Impact Factor
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Proceedings of the 2010 Symposium on Interactive 3D Graphics, SI3D 2010, February 19-21, 2010, Washington, DC, USA; 01/2010
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Proceedings of the ACM Symposium on Virtual Reality Software and Technology, VRST 2007, Newport Beach, California, USA, November 5-7, 2007; 01/2007
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Proceedings of the Eurographics Symposium on Rendering Techniques, Grenoble, France, 2007; 01/2007
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Shaw, Chris; Bartram, Lyn: Graphics Interface 2008 : proceedings, ACM, 185-192 (2008).
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Hart, John c.: ACM SIGGRAPH Asia 2008 papers, ACM, Art.129.1-8 (2008).
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ABSTRACT: Visibility computation is often the bottleneck when rendering indirect illumination. However, recent methods based on instant radiosity have demonstrated that accurate visibility is not required for indirect illumination. To exploit this insight, we cluster a large number of virtual point lights -- which represent the indirect illumination when using instant radiosity -- into a small number of virtual area lights. This allows us to compute visibility using recent real-time soft shadow algorithms. Such approximate and fractional from-area visibility is faster to compute and avoids banding when compared to exact binary from-point visibility. Our results show, that the perceptual error of this approximation is negligible and that we achieve real-time frame-rates for large and dynamic scenes.
Vision, Modeling, and Visualization Workshop (VMV), --- (2009).
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ABSTRACT: In this paper we evaluate the use of approximate visibility for efficient global illumination. Traditionally, accurate visibility is used in light transport. However, the indirect illumination we perceive on a daily basis is rarely of high frequency nature, as the most significant aspect of light transport in real-world scenes is diffuse, and thus displays a smooth gradation. This raises the question of whether accurate visibility is perceptually necessary in this case. To answer this question, we conduct a psychophysical study on the perceptual influence of approximate visibility on indirect illumination. This study reveals that accurate visibility is not required and that certain approximations may be introduced.
Symposium on Applied Perception in Graphics and Visualization (APGV), ACM (2009).
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Turk, Greg: Proceedings of ACM SIGGRAPH 2008, ACM, Art.90.1-8 (2008).
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ABSTRACT: Much research has gone into developing methods for enhancing the contrast of displayed 3D scenes. In the current study, we investigated the perceptual impact of an algorithm recently proposed by Ritschel et al.1 that provides a general technique for enhancing the perceived contrast in synthesized scenes. Their algorithm extends traditional image-based Unsharp Masking to a 3D scene, achieving a scene-coherent enhancement. We conducted a standardized perceptual experiment to test the proposition that a 3D unsharp enhanced scene was superior to the original scene in terms of perceived contrast and preference. Furthermore, the impact of different settings of the algorithm’s main parameters enhancement-strength (¸) and gradient size (¾) were studied in order to provide an estimate of a reasonable parameter space for the method. All participants preferred a clearly visible enhancement over the original, non-enhanced scenes and the setting for objectionable enhancement was far above the preferred settings. The effect of the gradient size ¾ was negligible. The general pattern found for the parameters provides a useful guideline for designers when making use of 3D Unsharp Masking: as a rule of thumb they can easily determine the strength for which they start to perceive an enhancement and use twice this value for a good effect. Since the value for objectionable results was twice as large again, artifacts should not impose restrictions on the applicability of this rule.
Rogowitz, Bernice E.; Pappas, Thrasyvoulos N.: Human Vision and Electronic Imaging XIV, IS\&T/SPIE's 21st Annual Symposium on Electronic Imaging, SPIE, 72400R-1-12 (2009).
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ABSTRACT: Physically plausible illumination at real-time framerates is often achieved using approximations. One popular example is ambient occlusion (AO), for which very simple and efficient implementations are used extensively in production. Recent methods approximate AO between nearby geometry in screen space (SSAO). The key observation described in this paper is, that screen-space occlusion methods can be used to compute many more types of effects than just occlusion, such as directional shadows and indirect color bleeding. The proposed generalization has only a small overhead compared to classic SSAO, approximates direct and one-bounce light transport in screen space, can be combined with other methods that simulate transport for macro structures and is visually equivalent to SSAO in the worst case without introducing new artifacts. Since our method works in screen space, it does not depend on the geometric complexity. Plausible directional occlusion and indirect lighting effects can be displayed for large and fully dynamic scenes at real-time frame rates.
ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, ACM, 75-82 (2009).
