Accessibility analysis using computer graphics hardware

Spitz, Steven; Requicha, Aristides A. G.

doi:10.1109/2945.879783

Cited by 32 publications

(11 citation statements)

References 24 publications

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“…Ambient occlusion, also known as accessibility mapping (e.g., Miller 1994, Zhukov et al 1998, Spitz and Requicha 2000, Iones et al 2003, is an approach which computes, for each point of the surface, the solid angle of directions in which the outside environment is locally visible. This solid angle gives an approximation of the amount of light arriving at the point from the outside environment and permits shadowing from extended light sources to be estimated, much like the sky view factor of Dubayah and Rich (1995).…”

Section: Horizon-based Illuminationmentioning

confidence: 99%

General sky models for illuminating terrains

Kennelly¹,

Stewart

2013

International Journal of Geographical Information Science

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Sky models are quantitative representations of natural luminance of the sky under various atmospheric conditions. They have been used extensively in studies of architectural design for nearly a century, and more recently for rendering objects in the field of computer graphics. The objectives of this paper are to (1) describe sky models, (2) demonstrate how map designers can render terrain under various sky models in a typical geographic information system (GIS), (3) illustrate potential enhancements to terrain renderings using sky models, and (4) discuss how sky models, with their well-established standards from a different discipline, might contribute to a virtual geographic environment (VGE).Current GIS hill-shading tools use the Lambertian assumption which can be related to a simple point light source at an infinite distance to render terrain. General sky models allow the map designer to choose from a gamut of sky models standardized by the International Commission on Illumination (CIE). We present a computer application that allows the map designer to select a general sky model and to use existing GIS tools to illuminate any terrain under that model. The application determines the orientations and weights of many discrete point light sources that, in the aggregate, approximate the illumination provided by the chosen sky model. We discuss specific enhancements to terrains that are shaded and shadowed with these general sky models, including additional detail of secondary landforms with soft shadows and more realistic shading contrasts. We also illustrate how non-directional illumination models result in renderings that lack the perceptual relief effect. Additionally, we argue that this process of creating hill-shaded visualizations of terrain with sky models shows parallels to other geo-simulations, and that basing such work on standards from the computer graphics industry shows potential for its use in VGE.

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Section: Horizon-based Illuminationmentioning

confidence: 99%

General sky models for illuminating terrains

Kennelly¹,

Stewart

2013

International Journal of Geographical Information Science

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“…A GAC is used to represent feasible angles of attack toward an object. The concept of GACs has been extensively investigated, and leads to promising results for the accessibility analysis of tools in many applications such as multi-axis machining, laser scanning and coordinate measuring machine (CMM) [12][13][14][15].…”

Section: Fast Assembly-tool Feasibility Analysismentioning

confidence: 99%

“…In particular, based on the concept of discrete GACs [14,15], a modified GAC is proposed in this research, named the global accessibility cone with depth (GAC d ). The GAC d consists of 180×360 pixels to make total 64,800 directions on a sphere.…”

Section: Fast Assembly-tool Feasibility Analysismentioning

confidence: 99%

Tool Selection-Embedded Optimal Assembly Planning

Chung¹,

Peng²

2011

PCEEA

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“…Raster visibility methods for computing the visible set for 3D object were targeting the building of a visibility matrix based on the discretized approximation of the solution space [Tarbox and Gottschlich 1996;Balasubramanian et al 2000;Spitz and Requicha 2000;Khardekar et al 2006]. The elements of the visibility matrix encode the visibility of discrete object surface entities from each sampled point in a quantized viewing sphere.…”

Section: A Set Of Triangular Facets For Each Facet Find the Set Of mentioning

confidence: 99%

Computing an exact spherical visibility map for meshed polyhedra

Liu

Ramani

2007

Proceedings of the 2007 ACM Symposium on Solid and Physical Modeling

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This paper considers computation of the exact visibility range (or the spherical visibility map) for a closed polyhedron whose boundary is represented as a triangle mesh. For each facet on the mesh, we calculate the set of view directions from which all the points on the facet can be seen from the exterior. The projection of those visible directions onto the unit sphere forms the visibility map for the facet. We show that the exact visibility map is a spherical arrangement of closed 0-cells, 1-cells, and 2-cells embedded on the surface of the unit sphere. Based on a provable method for calculating the potential occlusion regions of a facet, a vector visibility algorithm is developed for computing the exact solution of the spherical visibility map for a facet. Examples are given to illustrate our algorithm.

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Accessibility analysis using computer graphics hardware

Cited by 32 publications

References 24 publications

General sky models for illuminating terrains

General sky models for illuminating terrains

Tool Selection-Embedded Optimal Assembly Planning

Computing an exact spherical visibility map for meshed polyhedra

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