J. Stewart. Hierarchical visibility in terrains. Eurographics Rendering Workshop, pages 217--228, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....respect to a view cell is the region of space from where no point of the view cell can be seen, whereas the penumbra is the region of space from where some, but not all points of the view cell can be seen. become quite costly with respect to time and memory, but for certain scenes, like terrains [20] or building interiors [22] it is possible to use the a priori knowledge about the scene structure for visibility calculation. Cohen Or et al. 2] show an algorithm for densely occluded scenes that does not make use of occluder fusion. Several view cell visibility methods with occluder fusion ....

A. Stewart. Hierarchical Visibility in Terrains. Eurographics Rendering Workshop 1997.

....regions [7] or by exploiting vertical ray coherence for ray casting [27] Several methods incorporate level of detail (LOD) techniques to speed up rendering. Such LOD techniques can be embedded in multiresolution BSP trees [43] or combined with hierarchical visibility for culling occluded regions [42]. However, changing the LOD during an animation might result in visual discontinuities. This problem has led to the development of continuous LOD techniques [17, 29, 15] In [29] a continuous LOD rendering is obtained through on line simplification of the original mesh data while maintaining ....

A. J. Stewart. Hierarchical Visibility in Terrains. In Rendering Techniques '97 (Proc. 8th EG Workshop on Rendering), pp. 217--228, 1997.

....(e.g. Fun95, Fun96] Applications to global lighting simulation have also been demonstrated, e.g. TH93] Unfortunately these methods rely heavily on the properties of indoor scenes, and no direct generalization has been presented. Visibility for terrain models has also been treated (e.g. [Ste97]) Preprocessing algorithms capable of treating more general scenes have recently begun to emerge (e.g. COFHZ98, COZ98, WBP98] Nonetheless, they are currently restricted to occlusions caused by a single convex occluder at a time. Since they cannot Figure 1: Top: A 7.8 M poly forest scene ....

A. James Stewart. Hierarchical visibility in terrains. Eurographics Workshop on Rendering 1997, June 1997.

....information for each regions. Teller et al. 15, 16] partition indoor scenes into cells connected by portals and compute cell to cell visibility. Cohen Or et al.: 3] provide a modeling method for densely occluded city data sets and pre compute hidden buildings for each view cell. Stewart [14] presents a visibility algorithm for the case of terrain. Some other work are focusing on more general scenes [4, 17] However, occluders fusion is inherently difficult to be computed for a view cell and Shaufle et al.: 13] provide a solution by extending the blockers defined in their algorithm, ....

J. Stewart. Hierarchical visibility in terrains. Eurographics Rendering Workshop, pages 217--228, 1997.

....book [4] for a discussion and references. Wimmer et al. 8] render all geometry within a certain radius without occlusion culling. Then, image caching and ray casting is used for the distant geometry, resulting in complexity proportional to the number of pixels of the rendering window. Stewart [6] computes accurate horizons at all vertices in a terrain in a preprocessing step. Coorg and Teller [2] present a cell based technique that selects a small set of large occluders, and determines via supporting planes whether a bounding box of an object is hidden behind, i.e. in the shadow of, a ....

A. James Stewart. Hierarchical visibility in terrains. Eurographics Rendering Workshop 1997, pages 217--228, June 1997.

....corresponds to visibility determination from a point in infinity. Another application of VFP in global illumination techniques was studied by Sillion and Drettakis [155, 56] A lot of research has been devoted to visibility from point in 2D and 2 1 2 D dimensional environments such as terrains [128, 170, 43]. A recent algorithm for visibility determination in urban environments was described by Wonka and Schmalstieg [206] These problems can be usually thought of as involving one dimensional line space and so they are simpler to solve than the general VFP problems. Further in this chapter we ....

A. J. Stewart. Hierarchical visibility in terrains. In J. Dorsey and P. Slusallek, editors, Eurographics Rendering Workshop 1997, pages 217--228, New York City, NY, June 1997. Eurographics, Springer Wein. ISBN 3-211-83001-4.

....problems. It is generally easier to conservatively overestimate the set of potentially visible objects (PVS [1, 26] for a certain region of space (referred to as a viewcell throughout this paper) While effective methods exist to detect occlusions in indoor scenes [1, 26] and terrain models [24], in more general types of complex scenes previous approaches [4, 6, 21] consider single convex occluders only to determine objects, or portions of space, that are completely hidden from the viewcell. This is known as volume visibility. In many cases, objects are hidden due to the combination of ....

....Airey To appear in the SIGGRAPH 2000 conference proceedings et al. 1] and Teller et al. 26, 28] propose visibility preprocessing for indoor scenes. They identify objects that are visible through sequences of portals. Yagel et al. 31] apply similar ideas in 2D for visibility in caves. Stewart [24] provides a solution for the case of terrain. Unfortunately, these algorithms do not generalize to volume visibility for more general types of complex scenes. Conservative, but accurate, volume visibility computations for general scenes are limited to considering one convex occluder at a time for ....

Stewart, James, "Hierarchical Visibility in Terrains," Eurographics Rendering Workshop, June 1997, pp 217-228.

....a so called horizon map . This horizon map describes the horizon for a small number of directions (8 in the original paper) at each point in the height field. During rendering, the shadow test then simply determines whether the light direction is above or below the (interpolated) horizon. Stewart [26, 27] introduced a hierarchical approach to determine the visibility in terrains both for occlusion culling and shading. More recently, Stewart used a similar idea to simulate the shadowing in cloth [28] For the shadowing part of our paper, we use a concept similar to the original horizon map, but in ....

J. Stewart. Hierarchical visibility in terrains. In Rendering Techniques '97 (Proc. of Eurographics Workshop on Rendering) , pages 217--228, June 1997.

....of all the points horizons. Then the entire group is hidden if the viewpoint lies beyond and below this lower envelope in all directions in which it is visible from the group. Thus, a large area of the terrain can be classified with a single visibility test. Details are found in another paper [11], which describes hierarchical visibility testing in terrains. That paper uses horizons to eliminate from rendering almost all hidden parts of the terrain. As shown in Fig. 2, this can be quite effective, greatly reducing the number of rendered polygons. a) Rendered terrain (b) Overhead view ....

A. James Stewart, "Hierarchical visibility in terrains", in Eurographics Rendering Workshop, June 1997, pp. 217--228.

No context found.

J. Stewart. Hierarchical visibility in terrains. Eurographics Rendering Workshop, pages 217--228, 1997.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC