Steven Collins. Adaptive splatting for specular to diffuse light transport. proceedings of 5. Eurographics Workshop on Rendering, pages 119--135, Darmstadt 1994.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....rays with the scene are approximated by a linear system matrix. All these approaches extend a ray to finite width, which makes intersection, reflection and refraction calculations much more difficult. The combination of physically based BRDF s with these methods is a difficult problem. Collins [5] uses standard ray tracing but the connectivity between neighboring starting rays is explicitly maintained when propagating them through the scene. The distance to neighboring rays was used to determine a filter kernel size for deposition in a caustic lightmap. Connectivity is lost, though, when ....

Steven Collins. Adaptive Splatting for Specular to Diffuse Light Transport. In Fifth Eurographics Workshop on Rendering, pages 119--135, Darmstadt, Germany, June 1994.

....tracing [11] all extend a ray to a finite width. Lighting calculations can be done coherently over the extent of the ray, but intersection, reflection and refraction calculations are much more difficult. The combination of physically based BRDF s with these methods is a difficult problem. Collins [4] explicitly maintains connectivity between neighboring paths when they are traced through the scene. The distance to neighboring rays serves as a kernel size for splatting in a caustic lightmap. Connectivity is lost, however, when adjacent rays hit different objects leading to different ray trees. ....

Steven Collins. Adaptive Splatting for Specular to Diffuse Light Transport. In Fifth Eurographics Workshop on Rendering, pages 119--135, Darmstadt, Germany, June 1994.

.... caustics, the intensity attributed to a sampled light ray depends upon the convergence or divergence of the wavefront [13] Similarly, in illumination mapping, the flux carried by a ray from a light source must be deposited over an area on a surface s illumination map based on the density of rays [5]. Dull reflections may be modeled by filtering textures over a kernel which extends beyond the ray s actual footprint [2] In this paper, we introduce a novel approach for quickly and robustly tracking an approximation to a ray s footprint based on ray differentials. Ray tracing can be viewed ....

....in addition to tracing the ray, we can also trace the value of its derivatives with respect to the image plane. A first order Taylor approximation based on these derivatives gives an estimate of a ray s footprint. A few techniques for estimating ray density have been presented in the literature [2, 5, 13, 16], but ray differentials are faster, simpler, and more robust than these algorithms. In particular, because ray differentials are based on elementary differential calculus rather than on differential geometry or another mathematical foundation that has an understanding of the 3D world, the ....

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S. Collins. Adaptive Splatting for Specular to Diffuse Light Transport. Fifth Eurographics Workshop on Rendering, 119-135, 1994.

....is the fact that a large number of photons must be used to eliminate noise in the caustics. Heckbert [7] introduced a method that adaptively subdivided the illumination map into area elements (rexes) with a size corresponding to the local density of the photon hits. Chen et al. 3] and Collins [4] use a fixed illumination map. To eliminate noise they use different filter kernels to spread the energy from each photon onto several area elements. Jensen et al. 9] stored all photon hits explicitly in a photon map and avoided using the illumination map. Instead they introduced a new technique ....

Collins, Steven: "Adaptive Splatting for Specular to Diffuse Light Transport". In proceedings of 5. Eurographics Workshop on Rendering, pp. 119-135, Darmstadt 1994

....configurations efficiently. Some attempts have also been made for interactive display of globally illuminated scenes [29, 32] Finally, it is worth mentioning that specific methods have been developed for the rendering of caustics which are one of the more beautiful lighting phenomena (e.g. [5, 36]) However, they do not treat the entire breadth of all light transfers. 2 Overview In our new algorithm, we start by building the cluster hierarchy as in HRC. Refinement proceeds by examining each link (see Fig. 2) and deciding whether to refine based on the chosen criterion. During gather, we ....

S. Collins. Adaptive splatting for specular to diffuse light transport. 5th EG Workshop on Rendering, pages 119--135, June 1994. Darmstadt, Germany.

.... which is described mathematically by the radiance or rendering equation [9] can be roughly classified into two groups: the Monte Carlo [9, 25, 18] and the finite element approach [6, 8, 16] Of course, a number of hybrid techniques that combine aspects of both approaches are also available [26, 3]. 2.2 Stages The process of rendering can be divided into three distinct stages, which also roughly correspond to three different phases during rendering: scene description, lighting calculation, image rendering (see Figure 1) Shader Lighting Calculation Image Rendering LightSource Shader ....

....and Wavelet Radiosity [8, 7] as well as three Wavelet Radiance algorithms [16, 1] From the class of Monte Carlo algorithms simple path tracing [9] and Bidirectional Estimators [25] have been implemented. Several hybrid techniques like Irradiance Gradients [28, 27] and Backward BeamTracing [3] are also available. This collection of algorithms is the basis for much of our current work in this area. a) Monte Carlo (b) Wavelet Radiosity Fig. 3. Two example images computed with global illumination. For the left image Monte Carlo integration has been used to capture the strong specular ....

S. Collins. Adaptive splatting for specular to diffuse light transport. In S. Haas, S. Muller, G. Sakas, and P. Shirley, editors, Fifth EUROGRAPHICS Workshop on Rendering, pages 119--135, Darmstadt, June 1994.

....density estimation technique to deal with caustic maps, and our density estimation work can be considered an extension of their caustic map techniques to account for all illumination effects in a scene. Collins has one of the most sophisticated density estimation techniques for global illumination [5], but his method does not account for multiple diffuse reflections. Our strategy is similar to Heckbert s and Collins , but differs in that the meshing is delayed until all Monte Carlo particle tracing has been completed. This allows us to use all the information collected while estimating surface ....

.... Gamma x i ) where k 1 has unit volume. This generates a smoother estimate for f . An example kernel estimate is shown in Figure 2. Using kernel functions on the hit points is analogous to the idea of splatting in volume rendering [20] and is similar to the illumination ray tracing of Collins [5]. Silverman [16] notes that whatever properties the derivatives of k 1 have will be shared by f , so we can ensure a smooth estimate for f by choosing a smooth k 1 . Good choices for k 1 are similar to the choices used for splatting or pixel filtering. As in those applications the kernels should ....

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Steven Collins. Adaptive splatting for specular to diffuse light transport. In Proceedings of the Fifth Eurographics Workshop on Rendering, pages 119--135, June 1994.

....of luminaires and mirrors can cause an arbitrarily large number of virtual luminaires. This makes any method that preferentially treats areas covered by luminaires suspect because real and virtual luminaires are treated differently. Working backwards from the luminaires can be effective (e.g. [1, 15, 6]) but this method usually stores some information on the primitives which is problematic if the geometry is procedural. We could also use the image method[13] to account for specular transfer, but this is difficult when mirrors are not planar. Virtual luminaires are often not important. However, ....

Steven Collins. Adaptive splatting for specular to diffuse light transport. In Proceedings of the Fifth Eurographics Workshop on Rendering, pages 119--135, June 1994.

....at the light sources in the scene and record the interactions of these rays and the surfaces in the scene, depositing power on diffuse surfaces along the rays paths. In order to record this power, illumination maps (in the spirit of Arvo [Arvo86] are used. For details of the algorithm see [Collins94]. 3.1.1 Light Ray Distribution Light Source 3D Item Buffer Specular Object Figure 2: Item Buffer Construction. In order to determine the solid angle, about the light sources within the scene, which must be sampled, we use a technique similar to the item buffer of [Weghorst84] and the hemicube of ....

Collins S., "Adaptive Splatting for Specular to Diffuse Light Transport", Proceedings of the 5th Eurographics Workshop on Rendering, pp. 119-135, June 1994.

....estimation techniques (in a manner similar to that proposed here) and records illumination as particle hit points with the surfaces. The method proposed in this paper borrows from previous work; pencil tracing [STN87] and Ray Casting for Radiosity Shadows [Ase92] We extend our earlier efforts [Col94] which tracked the wavefront from a point light source to allow for wavefront tracking from area sources. Rays are sent from the area source (initially approximating the area source as a point source) and having determined a point of intersection, the intersected object acts as a shadow caustic ....

.... determination either (a) by using view dependent information and setting the resolution proportion to the projected area of the surface on the viewing plane [Hec90] or (b) using a view independent scheme where resolution is adaptively chosen according to the illuminance gradients on the surface [Col94]. In our current implementation we adopt a view dependent approach, and choose a resolution R x = R y = 2 n where n is chosen so that Amap Apix 2 where Amap is the area of an illumination map pixel projected into screen space and A pix the area of a pixel in screen space. a) b) c) ....

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Collins S., Adaptive Splatting for Specular to Diffuse Light Transport, Proceedings of the 5th Eurographics Workshop on Rendering, pp:119-135, June 1994.

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Steven Collins. Adaptive splatting for specular to diffuse light transport. proceedings of 5. Eurographics Workshop on Rendering, pages 119--135, Darmstadt 1994.

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S. Collins. Adaptive splatting for specular to diffuse light transport. In Fifth Eurographics Workshop on Rendering, pages 119--135, June 1994.

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Steven Collins. Adaptive splatting for specular to diffuse light transport. In Proceedings of the Fifth Eurographics Workshop on Rendering, pages 119--135, June 1994.

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Collins, S.: Adaptive Splatting for Specular to Diffuse Light Transport, Proceedings of the Fifth Eurographics Workshop on Rendering, 119-135, 1992.

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Collins, Steven: "Adaptive Splatting for Specular to Diffuse Light Transport". In proceedings of 5. Eurographics Workshop on Rendering, pp. 119-135, Darmstadt 1994.

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