Fast and exact direct illumination

Mora, Fernando Cobos; Aveneau, Lilian

doi:10.1109/cgi.2005.1500414

Cited by 6 publications

(10 citation statements)

References 12 publications

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“…Using our visibility framework, the soft shadows quality is optimal, whatever the zooming is, since the visibility queries are exact. It is worth underlying that we were not able to precompute correctly the visibility on the Panther scene using a non-minimal polytope like in [13] or [10]: Because of numerical instabilities, errors occur in the visibility data, leading to visual artifacts in soft shadows. Using the minimal polytope, we avoid to perform useless CSG operations, improving robustness.…”

Section: Resultsmentioning

confidence: 99%

“…Thanks to this formalism, we prove a major theorem on the representation of a set of lines by a convex polytope. Next, we propose a generalization of Mora's work [10], into a ndimensional visibility framework. Finally, as an application, we explain how it can be used to compute very high quality soft shadows.…”

Section: Toward a Global Visibility Frameworkmentioning

confidence: 99%

“…As a consequence it is used during the rendering step to query the visibility of L for each point on T visible from the camera. A simple algorithm to perform such a query is presented in [10]. It provides an exact polygonal subdivision of the visible parts of L from a given point.…”

Section: Application Overviewmentioning

confidence: 99%

“…This property is used by Teller [18] for computing visibility through a sequence of portals, or convex transparent polygons. Nirenstein [13] and Bittner [3] take into account occlusion to compute from-region visibility, further improved by Haumont [8] and Mora [11,10].…”

Section: The Dimension Problemmentioning

confidence: 99%

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A Framework for n-Dimensional Visibility Computations

Aveneau

Charneau

Fuchs

et al. 2011

Guide to Geometric Algebra in Practice

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This chapter introduces global visibility computation using Grassmann Algebra. Visibility computation is a fundamental task in computer graphics, as in many other scientific domains. While it is well understood in two dimensions, this does not remain true in higher dimensional spaces.Grassmann Algebra allows to think about visibility at a high level of abstraction, and to design a framework for solving visibility problems in any n-dimensional space, for n ≥ 2. Contrary to Stolfi's framework which allows only the representation of real lines, it's algebraic nature dealt naturally without any particular cases.This chapter shows how the space of lines can be defined as a projective space over the bivector vector space. Then line classification, a key point for the visibility computation, is achieved using the exterior product. Actually, line classification turns out to be equivalent to point vs. hyperplane classification relatively to a nondegenerate bilinear form. This ensures well-defined property and computationally robustness.Using the previous result, the lines stabbing a n-dimensional convex face are characterized. This set of lines appears to be the intersection of the decomposable bivectors set (i.e. bivectors that represent a line) and a convex polytope. Moreover, this convex polytope is proved to be minimal. This property allows useful algorithmic improvements.To illustrate the use of our framework in practice, we present the computation of soft shadows for 3-dimensional illuminated scene.

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Section: Resultsmentioning

confidence: 99%

Section: Toward a Global Visibility Frameworkmentioning

confidence: 99%

Section: Application Overviewmentioning

confidence: 99%

Section: The Dimension Problemmentioning

confidence: 99%

See 2 more Smart Citations

A Framework for n-Dimensional Visibility Computations

Aveneau

Charneau

Fuchs

et al. 2011

Guide to Geometric Algebra in Practice

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“…The two first practicable algorithms are provided by Nirenstein et al [25] and Bittner [26] (see [27] for details about the differences between the two solutions), and further improved by Haumont et al [28] and Mora et al [29] respectively.…”

Section: Exact From Polygon Visibilitymentioning

confidence: 99%

Analytic ambient occlusion using exact from-polygon visibility

Apostu¹,

Mora²,

Ghazanfarpour³

et al. 2012

Computers & Graphics

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This paper presents a new method to compute exact from-polygon visibility, as well as a possible application to the calculation of high quality ambient occlusion. The starting point of this work is a theoretical framework which allows to group lines together according to the geometry they intersect. By applying this study in the context of from-polygon visibility, we derive an analytical definition which permits us to group the view rays according to the first geometry they encounter. Our new algorithm encodes lazily the visibility from a polygon. Contrary to previous works on frompolygon visibility, our approach is very robust. For each point in the scene, the algorithm efficiently calculates the exact fragments of visible geometry. By combining this information with a analytical definition of ambient occlusion, we achieve results that are not sensitive to noise or other visual imperfections, contrary to ambient occlusion methods which are based either on sampling or visibility approximations.

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Generate Accurate Soft Shadows Using Complete Occluder Buffer

Cai

et al. 2015

2015 14th International Conference on Computer-Aided Design and Computer Graphics (CAD/Graphics)

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In this paper, we propose a novel approach to generate accurate soft shadows for complex virtual scenes in real time. A Multi-Layer Occluder buffer (MLO-buffer) is used in our algorithm, and it is determined by rendering the scene from the center of area light source. MLO-buffer records all the potential occluders in the scene. When calculating shadow factors, area light source is represented by a set of point samples, and MLO-buffer is traversed to figure out the visibility relations between an occludee and each light sample. Finally, the accurate soft shadows can be produced. The experimental results show that our algorithm can generate high-quality soft shadows in real time without making any assumption, like shape orientation or density distribution, on the area light source.

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Fast and exact direct illumination

Cited by 6 publications

References 12 publications

A Framework for n-Dimensional Visibility Computations

A Framework for n-Dimensional Visibility Computations

Analytic ambient occlusion using exact from-polygon visibility

Generate Accurate Soft Shadows Using Complete Occluder Buffer

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