D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE CG&A, 12(6):25--39, November 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....hierarchical methods with hierarchical base functions have been introduced. Nevertheless, these Galerkin algorithms need to store the kernel and solution discretization of the integral equation. In addition to the high complexity of accurate mesh generation for shadow representation [LTG92] such projections introduce a discretization error. From the domain of Monte Carlo simulation, algorithms without kernel discretization are available, using the random integration scheme for only projecting the solution onto a finite base. Similar to the random approaches, a deterministic ....

D. Lischinski, F. Tampieri, and D. Greenberg. Discontinuity Meshing for Accurate Radiosity. IEEE Computer Graphics & Applications, 12(6):25--39, 1992. 1

....be accurately represented by any given set of basis functions. This limitation manifests itself in the form of projection errors, commonly referred to as shadow leaks and light leaks in computer graphics. These errors can be reduced by using very expensive algorithms such as discontinuity meshing [LTG92] to choose a good set of basis functions. More often, the brute force approach of simply increasing the number of basis functions is used. However, this results in a linear increase in the number of equations and therefore a quadratic increase in the time complexity of the algorithms mentioned ....

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics & Applications, 12(6):25--39, November 1992.

....for efficient shadow volume calculations in dynamic scenes. Brotman and Badler [3] came up with a soft shadow version of Crow s algorithm where they generated shadow volumes for a number of light source samples and computed the overlap using a depth buffer algorithm. Discontinuity Meshing, e.g. [12], is another exact way for computing soft shadows in object space. Here surfaces are subdivided in order to determine areas where the visible part of the area light source is constant. William s shadow map algorithm [18] is the fundamental idea of most methods working on sampled representations ....

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics & Applications, 12(6):25--39, November 1992.

....for efficient shadow volume calculations in dynamic scenes. Brotman and Badler [3] came up with a soft shadow version of Crow s algorithm where they generated shadow volumes for a number of light source samples and computed the overlap using a depth buffer algorithm. Discontinuity Meshing, e.g. [14], is another exact way for computing soft shadows in object space. Here surfaces are subdivided in order to determine areas where the visible part of the area light source is constant. William s shadow map algorithm [20] is the fundamental idea of most methods working on sampled representations of ....

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics & Applications, 12(6):25--39, November 1992.

....the viewcell. For this reason we periodically dump some of the intermediate virtual occluders into the dense set. This aggregate umbra algorithm bears some conceptual similarity to algorithms that compute shadow volumes from an area light source [4, 5] or even to discontinuity meshing methods [9, 15]. However, here we have two important advantages. First, the aggregate umbra does not necessarily have to be accurate, but conservative, and can thus be calculated significantly faster than area shadow algorithms. The other advantage lies in the effectiveness of the aggregation. While shadow ....

D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics & Applications, 12(6):25--39, November 1992.

....part of computational effort is spent on visibility. Although discrete approximations or sampling such as the z buffer or ray casting are often used in practice, analytic methods in which a continuous and precise solution is computed, can be very useful. In particular, for shadow calculations [16, 21, 6], or global illumination [10] the importance and utility of analytic visibility methods has been demonstrated. For virtual environments or games, graphics engines can now handle large polygon counts, even for low end platforms. In certain cases, for games engines or virtual reality, texture ....

....in such models and cannot always be reconstructed, and intersecting polygons are often present in the models. All of these properties can lead to robustness problems for geometric algorithms. 1. 1 Motivation To create shadow meshes, in particular for soft shadows, discontinuity meshing approaches [13, 6, 16] intersect shadow boundary surfaces, or swaths, with scene geometry. This approach is inevitably unrobust for large and degenerate scenes, since numerical problems quickly lead to loss of connectivity in the shadow mesh, or result in geometrical errors due to small features. We can observe ....

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D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE CGA, 12(6):25--39, November 1992.

....work was performed in [Camp91] in which the boundary between penumbral and unoccluded regions was computed. The resulting mesh was then used to build an approximation of radiance of constant radiance triangular elements. Similar work was performed by Chin and Feiner [ChFe92] Lischinski et al. [LiTG92] were the first to consider discontinuity surfaces interior to the penumbra, that signify a change in the topological view of the light source (e.g. the appearance or disappearance of a vertex or an edge in the visible portion of the source) They subsequently built a triangulation of the receiver ....

....of the source) They subsequently built a triangulation of the receiver surfaces based on the subdivision of this mesh, and constructed quadratic interpolants over these triangles. A different algorithm was presented by Heckbert [Heck92] in which a similar mesh is computed. Lischinski et al. [LiTG92] also merged the meshes from multiple sources, but no simplification was attempted. In this paper we extend the approach developed in [DrFi94, Dret94] In this approach the complete discontinuity mesh is calculated: the environment is segmented into regions (mesh faces) in which the topological ....

Lischinski D., Tampieri F., Greenberg D. P.: Discontinuity Meshing for Accurate Radiosity, IEEE Computer Graphics and Applications, November 1992.

....graphics in order to accurately, quantitively model features such as discontinuity, variations, etc. Derivative information has played an important role in mesh construction, guiding importance sampling and improving function interpolation. In previous work, Heckbert [40] and Lischinski et al. [54] identified derivative discontinuities in irradiance and used them to construct e#ective surface meshes. Irradiance gradient has been used to get higher order approximation of irradiance function. For example, Ward et al. 84] and Vedel [80, 81] estimated irradiance gradients by Monte Carlo path ....

Dani Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

.... Probabilistic methods [18] have also been presented to manage very complex scenes and lead to other animation algorithms [3] In the same time, the complexity of the function bases used to represent the illumination function in radiosity has been reduced by hierarchical and adaptive methods [4, 15, 19, 20]. Finally other function bases [1, 14, 23, 27, 29, 30] have been found to represent the illumination function but few animation methods based on these have been presented until now. Some animation algorithms [10, 11] have tried to use the benefits offered by adaptive bases, by identifying the ....

D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity Meshing for Accurate Radiosity. In IEEE Computer Graphics, volume 12(6), pages 25--39, Nov. 1992.

....solve the problem, but it raises HW requirements as well. Therefore, the original method was modied [2] and more practical ways were found [3] EOEciency of the methods depends also on a space sorting process. BSP trees [4] are frequently applied for this purpose in recently published algorithms [5, 6, 7], We show how BSP trees and hemicube algorithm can be merged to the fast and accurate computation. 2 Hemicube and BSP In the classical HC method patches in environment are projected onto the faces of a hemicube. Patches are clipped against the hemicube edges to obtain the set of pixels the patch ....

Lischinski, D., Tampieri, F. and Greenberg, D.: "Discontinuity Meshing for Accurate Radiosity.", IEEE Computer Graphics and Applications, 12:9, Nov 1992, 25-39.

....to coincide as viewed from the point of evaluation. We will use the term conjunctive vertex for this situation, in homage to ancient astronomers. Examples of conjunctive vertices include the apparent intersection of three edges, two intrinsic vertices, or an intrinsic vertex and an apparent vertex [9, 14]. Figure 3(c) shows an example of a conjunctive vertex containing three apparent vertices and one intrinsic vertex. Despite the complexity of the interaction, the local behavior is still sufficient to compute the irradiance contribution. Our method seamlessly handles conjunctive vertices of ....

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

....assumes a constant radiosity distribution across each surface patch and finite element, then the values are interpolated across each mesh element. Meshing surfaces without considering the shadow structure can lead to inaccurate solutions and shadow leaks . The discontinuity meshing approach [17, 25, 30] was developed to avoid these problems. For each source, a discontinuity mesh is created on the scenes surfaces (receivers) The mesh includes all lines where the illumination function has discontinuities, including the effects of boundaries of multiple occluders. Meshing concerns have been a ....

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity Meshing for Accurate Radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

....shadow algorithms, which we touch on only briefly. Although a decade old, the survey by Woo et al. 32] is still an excellent reference. 2. 1 Object Based Methods Soft shadows can be computed using object space methods such as distributed ray tracing [5] and radiosity with discontinuity meshing [11, 17] or backprojection [7, 29] Stark et al. 28] describe analytic methods for computing soft shadows. These approaches are computationally intensive and are not suitable for fast soft shadow generation for complex scenes. Herf and Heckbert [12] combine a number of shadow images for each receiver ....

D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

....sources [1] or by point sampling the source itself [4, 15] This is prone to aliasing if an insufficient number of samples is used. Images of a higher quality can be achieved using algorithms that use shadow volumes and or discontinuity meshing to determine the exact vis ibility of a source [11, 10, 2, 3, 7, 5, 14, 6]. Such techniques are very expensive and have only been designed to compute exact visibility for polygonal environments. Finally, shadow maps have also been used to approximate soft shadows, most recently by convolving source and occluder images to produce a soft shadow texture[12, 13] Such ....

Lischinski, D., Tampieri, F., Greenberg, D., "Discontinuity Meshing for Accurate Radiosity", IEEE C.G. & Appl., 12(6), Nov. 1992.

....point light sources [1] or by point sampling the source itself [4, 15] This approach is subject to aliasing if too few samples are used. Images of a higher quality can be achieved using algorithms that use shadow volumes and or discontinuity meshing to determine the exact visibility of a source [2, 3, 5, 7, 9, 14]. These techniques are very expensive and have only been designed to compute exact visibility for polygonal environments. Finally, shadow maps have also been used to texture map soft shadows, either by pre calculating an approximation using multiple light source samples and combining them in an ....

Lischinski, D., Tampieri, F., Greenberg, D., "Discontinuity Meshing for Accurate Radiosity ", IEEE C.G. & Appl., 12(6), Nov. 1992.

....constructs radiance interpolants in ray space where the ray trees have the same topology. Discontinuity Meshing: Discontinuity meshing is the idea of explicitly representing function discontinuities in a mesh used to construct an approximation to the function. Heckbert [6] and Lischinski et al. [7, 8, 11] have used discontinuity meshing to drastically improve the accuracy of radiosity simulations. Salisbury et al. 12] used a discontinuity mesh containing sharp edges in an image in order to maintain the sharpness of these edges when the image is magnified. 2 Algorithm The goal of our previewer ....

Dani Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuitymeshing for accurate radiosity. IEEE Computer Graphics and Applications, 12(6):25-- 39, November 1992.

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D. Lischinski, F. Tampieri, and D. P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE CG&A, 12(6):25--39, November 1992.

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D.Lischinski, F.Tampieri and D.P.Greenberg, "Discontinuity Meshing for Accurate Radiosity," IEEE CG&A, 12(6), 1992, pp.25--39.

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D. Lischinski, F. Tampieri, and D. P. Greenberg, "Discontinuity meshing for accurate radiosity," IEEE Computer Graphics and Applications, vol. 12, no. 6, pp. 25--39, November 1992.

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Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity Meshing for Accurate Radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

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Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity Meshing for Accurate Radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

No context found.

Daniel Lischinski, Filippo Tampieri, and Donald P. Greenberg. Discontinuity meshing for accurate radiosity. IEEE Computer Graphics and Applications, 12(6):25--39, November 1992.

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Dani Lischiniski, Fillipino Tampeiri, Donald P. Greenberg, "Discontinuity meshing for accurate radiosity", IEEE Computer graphics and applications, November 1992. pp 25-39.

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D. Lischinski, F. Tampieri, and D. P. Greenberg, "Discontinuity Meshing for Accurate Radiosity", IEEE Computer Graphics and Applications, 12(6), pp. 25--39 (1992).

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D. Lischinski, F. Tampieri, and D. Greenberg (1992) Discontinuity meshing for accurate radiosity, IEEE Computer Graphics & Applications 12:6, pp. 25-39.

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