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85
Adaptive Display Algorithm for Interactive Frame Rates During Visualization of Complex Virtual Environments
, 1993
"... We describe an adaptive display algorithm for interactive frame rates during visualization of very complex virtual environments. The algorithm relies upon a hierarchical model representation in which objects are described at multiple levels of detail and can be drawn with various rendering algorithm ..."
Abstract

Cited by 397 (10 self)
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We describe an adaptive display algorithm for interactive frame rates during visualization of very complex virtual environments. The algorithm relies upon a hierarchical model representation in which objects are described at multiple levels of detail and can be drawn with various rendering algorithms. The idea behind the algorithm is to adjust image quality adaptively to maintain a uniform, userspecified target frame rate. We perform a constrained optimization to choose a level of detail and rendering algorithm for each potentially visible object in order to generate the "best" image possible within the target frame time. Tests show that the algorithm generates more uniform frame rates than other previously described detail elision algorithms with little noticeable difference in image quality during visualization of complex models. CR Categories and Subject Descriptors: [Computer Graphics]: I.3.3 Picture/Image Generation  viewing algorithms; I.3.5 Computational Geometry and Object...
Hierarchical Image Caching for Accelerated Walkthroughs of Complex Environments
, 1996
"... We present a new method that utilizes path coherence to accelerate walkthroughs of geometrically complex static scenes. As a preprocessing step, our method constructs a BSPtree that hierarchically partitions the geometric primitives in the scene. In the course of a walkthrough, images of nodes at v ..."
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Cited by 157 (8 self)
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We present a new method that utilizes path coherence to accelerate walkthroughs of geometrically complex static scenes. As a preprocessing step, our method constructs a BSPtree that hierarchically partitions the geometric primitives in the scene. In the course of a walkthrough, images of nodes at various levels of the hierarchy are cached for reuse in subsequent frames. A cached image is reused by texturemapping it onto a single quadrilateral that is drawn instead of the geometry contained in the corresponding node. Visual artifacts are kept under control by using an error metric that quantifies the discrepancy between the appearance of the geometry contained in a node and the cached image. The new method is shown to achieve speedups of an order of magnitude for walkthroughs of a complex outdoor scene, with little or no loss in rendering quality. CR Categories and Subject Descriptors: I.3.3 [Computer Graphics ]: Picture/Image Generation  Display algorithms; I.3.7 [Computer Graphi...
Portals and Mirrors: Simple, Fast Evaluation of Potentially Visible Sets
 Symposium on Interactive 3D Graphics
, 1995
"... We describe an approach for determining potentially visible sets in dynamic architectural models. Our scheme divides the models into cells and portals, computing a conservative estimate of which cells are visible at render time. The technique is simple to implement and can be easily integrated into ..."
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Cited by 133 (0 self)
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We describe an approach for determining potentially visible sets in dynamic architectural models. Our scheme divides the models into cells and portals, computing a conservative estimate of which cells are visible at render time. The technique is simple to implement and can be easily integrated into existing systems, providing increased interactive performance on large architectural models.
Multiresolution Modeling for Fast Rendering
 PROCEEDINGS OF GRAPHICS INTERFACE
, 1994
"... Three dimensional scenes are typically modeled using a single, fixed resolution model of each geometric object. Renderings of such a model are often either slow or crude, however: slow for distant objects, where the chosen detail level is excessive, and crude for nearby objects, where the detail lev ..."
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Cited by 103 (5 self)
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Three dimensional scenes are typically modeled using a single, fixed resolution model of each geometric object. Renderings of such a model are often either slow or crude, however: slow for distant objects, where the chosen detail level is excessive, and crude for nearby objects, where the detail level is insufficient. What is needed is a multiresolution model that represents objects at multiple levels of detail. With a multiresolution model, a rendering program can choose the level of detail appropriate for the object's screen size so that less time is wasted drawing insignificant detail. The principal challenge is the development of algorithms that take a detailed model as input and automatically simplify it, while preserving appearance. Multiresolution techniques can be used to speed many applications, including real time rendering for architectural and terrain simulators, and slower, higher quality rendering for entertainment and radiosity. This paper surveys existing multiresolutio...
RING: A ClientServer System for MultiUser Virtual Environments
 Symposium on Interactive 3D Graphics
, 1995
"... This paper describes the clientserver design, implementation and experimental results for a system that supports realtime visual interaction between a large number of users in a shared 3D virtual environment. The key feature of the system is that serverbased visibility algorithms compute potentia ..."
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Cited by 75 (2 self)
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This paper describes the clientserver design, implementation and experimental results for a system that supports realtime visual interaction between a large number of users in a shared 3D virtual environment. The key feature of the system is that serverbased visibility algorithms compute potential visual interactions between entities representing users in order to reduce the number of messages required to maintain consistent state among many workstations distributed across a widearea network. When an entity changes state, update messages are sent only to workstations with entities that can potentially perceive the change  i.e., ones to which the update is visible. Initial experiments show a 40x decrease in the number of messages processed by client workstations during tests with 1024 entities interacting in a large densely occluded virtual environment. CR Categories and Subject Descriptors: [Computer Graphics]: I.3.7 ThreeDimensional Graphics and Realism  Virtual Reality. Add...
A Beam Tracing Approach to Acoustic Modeling for Interactive Virtual Environments
, 1998
"... Virtual environment research has focused on interactive image generation and has largely ignored acoustic modeling for spatialization of sound. Yet, realistic auditory cues can complement and enhance visual cues to aid navigation, comprehension, and sense of presence in virtual environments. A prima ..."
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Cited by 72 (13 self)
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Virtual environment research has focused on interactive image generation and has largely ignored acoustic modeling for spatialization of sound. Yet, realistic auditory cues can complement and enhance visual cues to aid navigation, comprehension, and sense of presence in virtual environments. A primary challenge in acoustic modeling is computation of reverberation paths from sound sources fast enough for realtime auralization. We have developed a system that uses precomputed spatial subdivision and "beam tree" data structures to enable realtime acoustic modeling and auralization in interactive virtual environments. The spatial subdivision is a partition of 3D space into convex polyhedral regions (cells) represented as a cell adjacency graph. A beam tracing algorithm recursively traces pyramidal beams through the spatial subdivision to construct a beam tree data structure representing the regions of space reachable by each potential sequence of transmission and specular reflection even...
Fast Computation of Shadow Boundaries Using Spatial Coherence and Backprojections
, 1994
"... This paper describes a fast, practical algorithm to compute the shadow boundariesin a polyhedral scene illuminated by a polygonal light source. The shadow boundaries divide the faces of the scene into regions such that the structure or "aspect" of the visible area of the light source is constant wit ..."
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Cited by 69 (5 self)
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This paper describes a fast, practical algorithm to compute the shadow boundariesin a polyhedral scene illuminated by a polygonal light source. The shadow boundaries divide the faces of the scene into regions such that the structure or "aspect" of the visible area of the light source is constant within each region. The paper also describes a fast, practical algorithm to compute the structure of the visible light source in each region. Both algorithms exploit spatial coherence and are the most efficient yet developed. Given the structure of the visible light source in a region, queries of the form "What specific areas of the light source are visible?" can be answered almost instantly from any point in the region. This speeds up by several orders of magnitude the accurate computation of first level diffuse reflections due to an area light source. Furthermore, the shadow boundaries form a good initial decomposition of the scene for global illumination computations. CR category: I.3.7 [Co...
Network Topologies for Scalable MultiUser Virtual Environments
, 1996
"... This paper investigates tradeoffs of different network topologies and messaging protocols for multiuservirtual environment systems. We present message distribution techniques appropriate for constructing scalable multiuser systems for a variety of network characteristics. Hierarchical system desi ..."
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Cited by 68 (0 self)
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This paper investigates tradeoffs of different network topologies and messaging protocols for multiuservirtual environment systems. We present message distribution techniques appropriate for constructing scalable multiuser systems for a variety of network characteristics. Hierarchical system designs utilizing servers that manage message distribution for entities in separate regions of a virtual environment are described that scale to arbitrary numbers of simultaneous users. Experimental results show that the rate of messages processed by server workstations in this system design are less than using previously described approaches. 1. Introduction With the recent increases in network bandwidth and graphics performance in desktop computers, there is a growing interest in distributed visual simulation systems that allow multiple users to interact in a shared 3D virtual environment. Users on workstations connnected by a widearea network run an interactive 3D graphics interface program...
Conservative Visibility Preprocessing using Extended Projections
, 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 perm ..."
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Cited by 64 (1 self)
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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 reproject 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 hardtotreat 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 viewfrustum culling only, without the computational overhead of online occlusion culling.
Hellytype theorems and generalized linear programming
 DISCRETE COMPUT. GEOM
, 1994
"... This thesis establishes a connection between the Helly theorems, a collection of results from combinatorial geometry, and the class of problems which we call Generalized Linear Programming, or GLP, which can be solved by combinatorial linear programming algorithms like the simplex method. We use the ..."
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Cited by 60 (0 self)
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This thesis establishes a connection between the Helly theorems, a collection of results from combinatorial geometry, and the class of problems which we call Generalized Linear Programming, or GLP, which can be solved by combinatorial linear programming algorithms like the simplex method. We use these results to explore the class GLP and show new applications to geometric optimization, and also to prove Helly theorems. In general, a GLP is a set...