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214
Efficient ray tracing of volume data
 ACM Transactions on Graphics
, 1990
"... Volume rendering is a technique for visualizing sampled scalar or vector fields of three spatial dimensions without fitting geometric primitives to the data. A subset of these techniques generates images by computing 2D projections of a colored semitransparent volume, where the color and opacity at ..."
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Cited by 392 (5 self)
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Volume rendering is a technique for visualizing sampled scalar or vector fields of three spatial dimensions without fitting geometric primitives to the data. A subset of these techniques generates images by computing 2D projections of a colored semitransparent volume, where the color and opacity at each point are derived from the data using local operators. Since all voxels participate in the generation of each image, rendering time grows linearly with the size of the dataset. This paper presents a fronttoback imageorder volumerendering algorithm and discusses two techniques for improving its performance. The first technique employs a pyramid of binary volumes to encode spatial coherence present in the data, and the second technique uses an opacity threshold to adaptively terminate ray tracing. Although the actual time saved depends on the data, speedups of an order of magnitude have been observed for datasets of useful size and complexity. Examples from two applications are given: medical imaging and molecular graphics.
A progressive refinement approach to fast radiosity image generation
 Computer Graphics
, 1988
"... A reformulated radiosity algorithm is presented that produces initial images in time linear to the number of patches. The enormous memory costs of the radiosity algorithm are also eliminated by computing formfactors onthefly. The technique is based on the approach of rendering by progressive ref ..."
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Cited by 266 (5 self)
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A reformulated radiosity algorithm is presented that produces initial images in time linear to the number of patches. The enormous memory costs of the radiosity algorithm are also eliminated by computing formfactors onthefly. The technique is based on the approach of rendering by progressive refinement. The algorithm provides a useful solution almost immediately which progresses gracefully and continuously to the complete radiosity solution. In this way the competing demands of realism and interactivity are accommodated. The technique brings the use of radiosity for interactive rendering within reach and has implications for the use and development of current and future graphics workstations.
Interactive ray tracing
 In Symposium on interactive 3D graphics
, 1999
"... University of Utah, We examine a rendering system that interactively ray traces an image on a conventional multiprocessor. The implementation is “brute force ” in that it explicitly traces rays through every screen pixel, yet pays careful attention to system resources for acceleration. The design of ..."
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Cited by 176 (28 self)
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University of Utah, We examine a rendering system that interactively ray traces an image on a conventional multiprocessor. The implementation is “brute force ” in that it explicitly traces rays through every screen pixel, yet pays careful attention to system resources for acceleration. The design of the system is described, along with issues related to material models, lighting and shadows, and frameless rendering. The system is demonstrated for several different types of input scenes.
Multilevel ray tracing algorithm
"... We propose new approaches to ray tracing that greatly reduce the required number of operations while strictly preserving the geometrical correctness of the solution. A hierarchical “beam” structure serves as a proxy for a collection of rays. It is tested against a kdtree representing the overall sc ..."
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Cited by 164 (2 self)
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We propose new approaches to ray tracing that greatly reduce the required number of operations while strictly preserving the geometrical correctness of the solution. A hierarchical “beam” structure serves as a proxy for a collection of rays. It is tested against a kdtree representing the overall scene in order to discard from consideration the subset of the kdtree (and hence the scene) that is guaranteed not to intersect with any possible ray inside the beam. This allows for all the rays inside the beam to start traversing the tree from some node deep inside thus eliminating unnecessary operations. The original beam can be further subdivided, and we can either continue looking for new optimal entry points for the subbeams, or we can decompose the beam into individual rays. This is a hierarchical process that can be adapted to the geometrical complexity of a particular view direction allowing for efficient geometric antialiasing. By amortizing the cost of partially traversing the tree for all the rays in a beam, up to an order of magnitude performance improvement can be achieved enabling interactivity for complex scenes on ordinary desktop machines.
A survey of shadow algorithms
 IEEE Computer Graphics and Applications
, 1990
"... Essential to realistic and visually appealing images, shadows are difficult ta compute in most display environments. This survey characterizes the various types of shadows. It also describes most existing shadow algorithms and discusses their complexities, advantages, and shommings. We examine herd ..."
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Cited by 147 (3 self)
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Essential to realistic and visually appealing images, shadows are difficult ta compute in most display environments. This survey characterizes the various types of shadows. It also describes most existing shadow algorithms and discusses their complexities, advantages, and shommings. We examine herd shadows, soft shadbws, shadows of transparent objects, and shadows for complex modeling primitives. For each type, we examine shadow algorithms within various rendswing techniques. This survey attempts to provide readem with enough background and insight on the various rmthods to dow them to choose the algorithm best wpuited to their W. We also hope that our analysis will h&p identify the a m that need more research and point bo possible sotutkms. A shadowa region of relative darkness within an not necessarily attenuate the light it occludes. In fact, illuminated regionoccurs when an object totally or it can concentrate light. However, as is traditional in partially occludes the light. A transparent object does image synthesis, lve will consider a region to be in
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 108 (14 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...
Ray Tracing Animated Scenes Using Coherent Grid Traversal
 Proceedings of ACM SIGGRAPH
"... model (78K triangles). c) Animated windup toys (11K triangles) walking and jumping incoherently around each other. d) A rigidbody dynamics simulation of marbles (8.8K triangles). e) A complex scene of 174K animated triangles, where a fairy and a dragonfly dance through an animated forest. Scenes a ..."
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Cited by 104 (25 self)
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model (78K triangles). c) Animated windup toys (11K triangles) walking and jumping incoherently around each other. d) A rigidbody dynamics simulation of marbles (8.8K triangles). e) A complex scene of 174K animated triangles, where a fairy and a dragonfly dance through an animated forest. Scenes are rebuilt from scratch every frame, allowing fully dynamic animation. Including shading, texturing, and hard shadows, as used in the above images, we can render these scenes at 1024 × 1024 pixels with 15.3, 7.8, 10.2, 26.2, and 1.4 frames per second on a dual 3.2 GHz Xeon. Excluding shading, texturing, and shadows, we achieve 34.5, 15.8, 29.3, 57.1, and 3.4 frames per second. We present a new approach to interactive ray tracing of moderatesized animated scenes based on traversing frustumbounded packets of coherent rays through uniform grids. By incrementally computing the overlap of the frustum with a slice of grid cells, we accelerate grid traversal by more than a factor of 10, and achieve ray tracing performance competitive with the fastest known packetbased kdtree ray tracers. The ability to efficiently rebuild the grid on every frame enables this performance even for fully dynamic scenes that typically challenge interactive ray tracing systems. 1 Introduction and Related
Backward Ray Tracing
 In ACM SIGGRAPH ’86 Course Notes  Developments in Ray Tracing
, 1986
"... Introduction Ray tracing has become a very popular method for image synthesis due to its unparalleled flexibility and its ability the generate images of high quality and realism. Simulation of effects such as reflection and refraction have been the hallmarks of ray tracing since its introduction [5 ..."
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Cited by 99 (1 self)
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Introduction Ray tracing has become a very popular method for image synthesis due to its unparalleled flexibility and its ability the generate images of high quality and realism. Simulation of effects such as reflection and refraction have been the hallmarks of ray tracing since its introduction [5]. With the advent of stochastic ray tracing [2], the range of effects expanded to include motion blur, soft shadows, depth of field, and both blurry reflections and translucency. A notable omission from the repertoire of ray tracing, however, is diffuse reflection of indirect light. Though several new algorithms have been introduced which simulate multiple diffuse reflections of light in polygonal environments [1, 4], ray tracing continues to neglect these higher order effects, and consequently falls short of a truly global model of illumination. These notes describe a simple extension to ray tracing which takes a first step toward alleviating this deficiency. The problem addressed
RealTime Acoustic Modeling for Distributed Virtual Environments
, 1999
"... Realistic acoustic modeling is essential for spatializing sound in distributed virtual environments where multiple networked users move around and interact visually and aurally in a shared virtual world. Unfortunately, current methods for computing accurate acoustical models are not fast enough for ..."
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Cited by 77 (11 self)
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Realistic acoustic modeling is essential for spatializing sound in distributed virtual environments where multiple networked users move around and interact visually and aurally in a shared virtual world. Unfortunately, current methods for computing accurate acoustical models are not fast enough for realtime auralization of sounds for simultaneously moving sources and receivers. In this paper, we present three new beam tracing algorithms that greatly accelerate computation of reverberation paths in a distributed virtual environment by taking advantage of the fact that sounds can only be generated or heard at the positions of "avatars" representing the users. The prioritydriven beam tracing algorithm performs a bestfirst search of a cell adjacency graph, and thus enables new termination criteria with which all early reflection paths can be found very efficiently. The bidirectional beam tracing algorithm combines sets of beams traced from pairs of avatar locations to find reverberation paths between them while requiring significantly less computation than previous unidirectional algorithms. The amortized beam tracing algorithm computes beams emanating from boxshaped regions of space containing predicted avatar locations and reuses those beams multiple times to compute reflections paths as each avatar moves inside the box. Cumulatively, these algorithms enable speedups of approximately two orders of magnitude over previous methods. They are incorporated into a timecritical multiprocessing system that allocates its computational resources dynamically in order to compute the highest priority reverberation paths between moving avatar locations in realtime with graceful degradation and adaptive refinement.
Modeling acoustics in virtual environments using the uniform theory of diffraction
 ACM Computer Graphics, SIGGRAPH’01 Proceedings
, 2001
"... Realistic modeling of reverberant sound in 3D virtual worlds provides users with important cues for localizing sound sources and understanding spatial properties of the environment. Unfortunately, current geometric acoustic modeling systems do not accurately simulate reverberant sound. Instead, they ..."
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Cited by 72 (10 self)
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Realistic modeling of reverberant sound in 3D virtual worlds provides users with important cues for localizing sound sources and understanding spatial properties of the environment. Unfortunately, current geometric acoustic modeling systems do not accurately simulate reverberant sound. Instead, they model only direct transmission and specular reflection, while diffraction is either ignored or modeled through statistical approximation. However, diffraction is important for correct interpretation of acoustic environments, especially when the direct path between sound source and receiver is occluded. The Uniform Theory of Diffraction (UTD) extends geometrical acoustics with diffraction phenomena: illuminated edges become secondary sources of diffracted rays that in turn may propagate through the environment. In this paper, we propose an efficient way for computing the acoustical effect of diffraction paths using the UTD for deriving secondary diffracted rays and associated diffraction coefficients. Our main contributions are: 1) a beam tracing method for enumerating sequences of diffracting edges efficiently and without aliasing in densely occluded polyhedral environments; 2) a practical approximation to the simulated sound field in which diffraction is considered only in shadow regions; and 3) a realtime auralization system demonstrating that diffraction dramatically improves the quality of spatialized sound in virtual environments.