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1

Image-based illumination on the GPU

Barsi A., Szirmay-Kalos L., Szécsi L.

Machine Graphics and Vision

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2005

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Vol. 14, No. 2

159-169

EN

In many computer graphics applications it is desirable to augment virtual objects with high dynamic range images representing the real environment. In order to provide an illusion that virtual objects are part of the real scene, illumination of the environment should be taken into account when rendering them. Proper calculation of the illumination from an environment map may be extremely expensive if we wish to account for occlusion, self shadowing and specular materials. In this paper we present a method that performs all the calculations on a per-frame basis, and is already real-time on non-cutting-edge hardware.

2

Generalized multiple importance sampling for Monte-Carlo global illumination

Csonka F., Szirmay-Kalos L., Antal G.

Machine Graphics and Vision

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2002

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Vol. 11, No. 1

3-20

EN

The global illumination or transport problems can be considered as a sequence of integrals, while their Monte-Carlo solutions - as different sampling techniques. Multiple importance sampling takes advantage of different sampling strategies, and combines the results obtained with them to estaglish a quasi-optimal sampling for Monte--Carlo quadratures. This offers a combination of totally different global illumination algorithms which preserves thier strengths. However, implementation of this general concept poses two problems. The solution of the global illumination problem does not contain a single integral, but a sequence of integrals that are approximated simulataneously. One objective of this paper is to generalize the fundamental theory of multiple importance sampling to sequences of integrals. The cost of the computation and the contribution of a single integral to the final result vary. On the other hand, different methods compute a sample with different computational burdens, which should also be taken into account. This paper attacks this problem and introduces the concept of computational cost in multiple importance sampling. The theoretical results are used to combine bi--directional path tracing and ray-bundle based stochastic iteration. We conclude that the combined method preserves the high initial speed of stochastic interation, but can also accurately compute the specular light paths through bi-directional path tracing.

3

Quadratic shading and its hardware implementation

Abbas A. M., Szirmay-Kalos L., Horvath T., Foris T.

Machine Graphics and Vision

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2000

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Vol. 9, No. 4

825-839

EN

Rendering systems often represent curved surfaces as a mesh of planar polygons that are shaded to restore a smooth appearance. Gouraud shading uses linear color interpolation and its hardware implementation is relatively easy, but it handles specular highlights incorrectly and introduces annoying artifacts called Mach banding over the edges of the polygon mesh. In software rendering, Phong shading has been more popular, because it can realistically handle specular materials. Since it requires the rendering equation to be evaluated for each pioxel, its hardware support poses problems. This paper presents a nonlinear, i.e. quadratic interpilation scheme which is in between Gouraud shading and Phong shading. It can also be implemented by hardware means as Gouraud shading, but its shading quality is comparable with that of the Phong shading. A software simulation and VHDL description of the shading hardware are also presented.

4

Reflectance models by pumping up the albedo function

Neumann L., Neumann A., Szirmay-Kalos L.

Machine Graphics and Vision

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1999

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Vol. 8, No. 1

3-17

EN

The paper introduces a method, called the albedo pumping-up, to derive new, physically plausible BRDFs from an axisting one or from any symmetric function. This operation can be applied recursively arbitrary number of times. An important application of this operation is the transformation of the Phong and Blinn models in order to make them produce metallic effects. The paper also examines the albedo function of reflectance models and comes to the conclusion that widely used models violate energy balance at grazing angles.

5

Non-diffuse, random-walk radiosity algorithm with linear basis functions

Szirmay-Kalos L., Foris T., Purgathofer W.

Machine Graphics and Vision

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1998

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Vol. 7, No. 1/2

475-484

EN

This paper presents an efficient method to solve the general rendering equation, using a combined finite element and quasi-random walk approach. Applying point collocation method, the surfaces are decomosed into planar patches where the directional distribution of the radiance is assumed to be a linear combination of the disrtibutions at the vertices. The direction dependet radiance function of the vertces is then computed by random of quasi-random walk.

6

Interactive volume rotation

Csebfalvi B., Szirmay-Kalos L.

Machine Graphics and Vision

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1998

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Vol. 7, No. 4

793-806

EN

In this paper a new volume rendering method is presented which provides real-time rotation without using any acceleration hardware. The algorithm is based on the efficient handling of empty voxels, where according to the opacity values a 3D binary mask is generated indicating the locations of the non-transparent voxels. Ray casting is performed on this binary mask which is rotated rapidly by shear-warp factorization and an incremential aligment technique. The location of non-zero bit hit by a ray is mapped onto the corresponding voxel location in the orginal classified volume, in order to get the opacity and color values in the given samples point. The technique proposed for rotating and sampling the binary mask exploits only the standard ALU operations providing interactive frame rates even on low cost machines.