Visibility Map determination using Angle preprocessing (original) (raw)

Visibility preprocessing for interactive walkthroughs

ACM SIGGRAPH Computer Graphics, 1991

The number of polygons comprising interesting architectural models is many more than can be rendered at interactive frame rates. However, due to occlusion by opaque surfaces (e.g., walls), only a small fraction of atypical model is visible from most viewpoints.

Accurate scene display by using visibility maps

1999

A tool permitting to improve various steps of the visualisation process is presented in this paper. More precisely, this tool should concern the phase of preparing visualisation and also the visualisation phase itself. The tool presented in the paper, named visibility map, is based on the use of planar maps containing information on visibility and lighting, together with adjacency information inherent to planar maps. The proposed structure should permit to simplify the user's work, to accelerate some phases of visualisation and to improve the quality of produced images. In particular, this method permits to display a scene with ray tracing-like quality images, with very efficient antialiasing.

Conservative visibility preprocessing for walkthroughs of complex urban scenes

Proceedings of the ACM symposium on Virtual reality software and technology - VRST '00, 2000

Visibility preprocessing is a useful method to reduce the complexity of scenes to be processed in real-time, and so enhances the overall rendering performance for interactive visualization of virtual environments. In this paper, we propose an efficient visibility preprocessing method. The proposed method is able to handle more general environments, like urban environments , and remove invisible polygons jointly blocked by multiple occluders. The proposed method requires O(nm) time and O(n+m) space. By selecting a suitable value for m, user can select a suitable level of trade-off between the preprocessing time and the quality of the computational result. In the proposed method, we assume that navigatable areas in virtual environments are partitioned into rectangular parallelepiped cells or sub-worlds. To preprocess the visibility of each polygon for a given partitioned cell, we should determine at least the area-to-area visibility. That is inherently a four-dimensional problem. In the proposed method, we efficiently express four-dimensional visibility information on two-dimensional spaces and keep it within a ternary tree, which is conceptually similar to a BSP(Binary Space Partitioning) tree, by exploiting the characteristics of conservative visibility.

Visibility Computations for Real-Time Rendering in General 3D Environments

Sichtbarkeitsberechnungen sind essentielle Verfahren im Bereich der Computergrafik, notwendig für verschnellerte Darstellung in der Form von Visibility Culling, wie auch für realistische Beleuchtung. Visibility Culling, das den Hauptfokus dieser Arbeit darstellt, ist eine Technik die Ouput-Sensitivität erreichen will, indem nur die sichtbaren Primitive zur Grafikkarte gesandt werden. Trotz der rasanten Entwicklung der Grafikkarten ist Visibility Culling von großer Bedeutung für viele Applikationen, wie Spieleprogrammierung oder Architektur-Design, weil auch die Szenekomplexität entsprechend anwächst. Das Lösen des Sichtbarkeitsproblems war über viele Jahre hinweg ein wichtiges Thema, und unzählige Methoden wurden vorgeschlagen. Interessanterweise gibt es trotzdem immer noch offene Probleme wissenschaftlicher Art, und viele Algorithmen sind entweder unpraktisch oder nur verwendbar für bestimmte Szenenkonfigurationen, wodurch ihre weitläufige Verbreitung verhindert wurde. Sichtbarkeitsberechnungen werden auch benötigt um komplexe Lichtinteraktionen in der Szene zu lösen, von weichen und harten Schatten bis zu Ambient Occlusion und voller Globalen Beleuchtung. Es ist eine riesige Herausforderung, hunderte bis tausende Visibilityanfragen im Bruchteil einer Sekunde zu beantworten um Echtzeit-Laufzeiten zu erreichen. Jenes zu schaffen ist ein Ziel dieser Arbeit.

Visibility Preprocessing for Complex 3D Scenes Using Hardware-Visibility Queries

International Journal of Image and Graphics, 2006

In cases of densely occluded urban scenes, it is useful to determine the visibility of scenes, since only small parts of the scene are visible from a given cell. In this paper, we introduce a new visibility preprocessing method that efficiently computes potentially visible objects for volumetric cells. The proposed method deals with general 3D polygonal models and invisible objects jointly blocked by multiple occluders. The proposed approach decomposes volume visibility into a set of point visibilities, and then computes point visibility using hardware-visibility queries. We carry out experiments on various large-scale scenes, and show the performance of our algorithm. Our performance analysis approach estimates the exact solution of volume visibility. From differences between the estimated solution and the proposed algorithms solution, we show that our algorithm seeks a tight overestimate of the potentially visible set (PVS).

The 3D visibility complex : a new approach to the problems of accurate visibility

Eurographics, 1996

Visibility computations are central in any computer graphics application. The most common way to reduce this expense is the use of approximate approaches using spatial subdivision. More recently analytic approaches efficiently encoding visibility have appeared for 2D (the visibility complex) and for certain limited cases in 3D (aspect graph, discontinuity meshes). In this paper we propose a new way of describing and studying the visibility of 3D space by a dual space of the 3D lines, such that all the visibility events are described. A new data-structure is defined, called the 3D visibility complex, which encapsulates all visibility events. This structure is global and complete since it encodes all visibility relations in 3D, and is spatially coherent allowing efficient visibility queries such as view extraction, aspect graph, discontinuity mesh, or form factor computation. A construction algorithm and suitable data structures are sketched.

Predetermining visibility priority in 3-D scenes (Preliminary Report)

ACM SIGGRAPH Computer Graphics, 1979

The principal calculation performed by all visible surface algorithms is the determination of the visible polygon at each pixel in the image. Of the many possible speedups and efficiencies found for this problem, only one published algorithm (developed almost a decade ago by a group at General Electric) took advantage of an observation that many visibility calculations could be performed without knowledge of the eventual viewing position and orientation— once for all possible images . The method is based on a “potential obscuration” relation between polygons in the simulated environment. Unfortunately, the method worked only for certain objects; unmanagable objects had to be manually (and expertly!) subdivided into managable pieces. Described in this paper is a solution to this problem which allows substantial a priori visibility determination for all possible objects without any manual intervention. The method also identifies the ( hopefully, few) visibility calculations which rema...

Analysis and visualization of visibility surfaces

Proceedings of the …, 2003

Visibility analysis has traditionally been restricted to point-to-point lineof-sight profiling or point-to-area viewshed analysis. This constrained view of visibility necessarily limits our ability to understand the visibility surface characteristics of the terrain. Recent research by the University of Edinburgh has resulted in the development of a Complete Intervisibility Database (CID), where viewsheds are stored for every point in a Digital Elevation Model (DEM). This paper builds on the CID concept and presents an exploratory examination of visibility surfaces. Two types of products are described: Descriptive Metrics and Tactical Decision Aids (TDAs). Descriptive Metrics characterize the visibility surface and include measures of cumulative visibility, slope of cumulative visibility, fragmentation, core area visibility, and ratio of cumulative visibility to core area visibility. These basic metrics can be combined and analysed to form TDAs, which represent higher level processing to support decisionmaking. TDAs include percent target visible and least/most visible route. This research represents a first step toward the longer-term goal of understanding the relationship between elevation and visibility.

Conservative visibility preprocessing using extended projections

Proceedings of the 27th annual conference on Computer graphics and interactive techniques - SIGGRAPH '00, 2000

Visualization of very complex scenes can be significantly accelerated using occlusion culling. In this paper we present a visibility preprocessing method which efficiently computes potentially visible geometry for volumetric viewing cells. We introduce novel extended projection operators, which permits efficient and conservative occlusion culling with respect to all viewpoints within a cell, and takes into account the combined occlusion effect of multiple occluders. We use extended projection of occluders onto a set of projection planes to create extended occlusion maps; we show how to efficiently test occludees against these occlusion maps to determine occlusion with respect to the entire cell. We also present an improved projection operator for certain specific but important configurations. An important advantage of our approach is that we can re-project extended projections onto a series of projection planes (via an occlusion sweep), and accumulate occlusion information from multiple blockers. This new approach allows the creation of effective occlusion maps for previously hard-to-treat scenes such as leaves of trees in a forest. Graphics hardware is used to accelerate both the extended projection and reprojection operations. We present a complete implementation demonstrating significant speedup with respect to view-frustum culling only, without the computational overhead of on-line occlusion culling.