A ray tracer has been developed that synthesizes images directly into the frequency domain. This makes it possible to use a simple vision model to control where rays are cast into a scene and to decide how rays should...
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A ray tracer has been developed that synthesizes images directly into the frequency domain. This makes it possible to use a simple vision model to control where rays are cast into a scene and to decide how rays should be spawned once an object is intersected. In this manner the most visible artifacts can be removed first and noise can be channeled into those areas of an image where it is least noticeable. The resulting image is produced in a format that is consistent with many image compression and transmission schemes.
This paper presents a hybrid model for animation of soft inelastic substance which undergo topological changes, e.g. separation and fusion and which fit with the objects they are in contact with. The model uses a part...
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ISBN:
(纸本)9780897917018
This paper presents a hybrid model for animation of soft inelastic substance which undergo topological changes, e.g. separation and fusion and which fit with the objects they are in contact with. The model uses a particle system coated with a smooth iso-surface that is used for performing collision detection, precise contact modeling and integration of response forces. The animation technique solves three problems inherent in implicit modeling. Firstly, local volume controllers are defined to insure constant volume deformation, even during highly inelastic processes such as splitting or fusion. Secondly, we avoid unwanted distance blending between disconnected pieces of the same substance. Finally, we simulate both collisions and progressive merging under compression between implicit surfaces that do not blend together. Parameter tuning is facilitated by the layered model and animation is generated at interactive rates.
We describe an extension of B-splines to surfaces of arbitrary topology, including arbitrary boundaries. The technique inherits many of the properties of B-splines: local control, a compact representation, and guarant...
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ISBN:
(纸本)9780897917018
We describe an extension of B-splines to surfaces of arbitrary topology, including arbitrary boundaries. The technique inherits many of the properties of B-splines: local control, a compact representation, and guaranteed continuity of arbitrary degree. The surface is specified using a polyhedral control mesh instead of a rectangular one;the resulting surface approximates the polyhedral mesh much as a B-spline approximates its rectangular control mesh. Like a B-spline, the surface is a single, continuous object. This is achieved by modeling the domain of the surface with a manifold whose topology matches that of the polyhedral mesh, then embedding this domain into 3-space using a basis-function/control-point formulation. We provide a constructive approach to building a manifold.
We present techniques for constructing approximate stochastic models of complicated dynamical systems for applications in interactivecomputergraphics. The models are designed to produce realistic interaction at low ...
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We present techniques for constructing approximate stochastic models of complicated dynamical systems for applications in interactivecomputergraphics. The models are designed to produce realistic interaction at low cost. We describe two kinds of stochastic models: continuous state (ARX) models and discrete state (Markov chains) models. System identification techniques are used for learning the input-output dynamics automatically, from either measurements of a real system or from an accurate simulation. The synthesis of behavior in this manner is several orders of magnitude faster than physical simulation. We demonstrate the techniques with two examples: (1) the dynamics of candle flame in the wind, modeled using data from a real candle and (2) the motion of a falling leaf, modeled using data from a complex simulation. We have implemented an interactive Java program which demonstrates real-time interaction with a realistically behaving simulation of a cartoon candle flame. The user makes the flame animation flicker by blowing into a microphone.
This paper presents new solutions to the following three problems in image morphing: feature specification, warp generation, and transition control. To reduce the burden of feature specification, we first adopt a comp...
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ISBN:
(纸本)9780897917018
This paper presents new solutions to the following three problems in image morphing: feature specification, warp generation, and transition control. To reduce the burden of feature specification, we first adopt a computer vision technique called snakes. We next propose the use of multilevel free-form deformations (MFFD) to achieve C2-continuous and one-to-one warps among feature point pairs. The resulting technique, based on B-spline approximation, is simpler and faster than previous warp generation methods. Finally, we simplify the MFFD method to construct C2-continuous surfaces for deriving transition functions to control geometry and color blending.
This paper describes the use of a World-in-Miniature (WIM) as a navigation and locomotion device in immersive virtual environments. The WIM is a hand-held miniature graphical representation of the virtual environment,...
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ISBN:
(纸本)9780897917018
This paper describes the use of a World-in-Miniature (WIM) as a navigation and locomotion device in immersive virtual environments. The WIM is a hand-held miniature graphical representation of the virtual environment, similar to a map cube. When the user moves an object in the WIM, the object simultaneously moves in the surrounding virtual environment. When the user moves an iconic representation of himself, he moves (flies) in the virtual environment. Flying the user in the full scale virtual world is confusing, because the user's focus of attention is in the miniature, not in the full scale virtual world. We present the novel technique of flying the user into the miniature, providing perceptual and cognitive constancy when updating the viewpoint.
Rendering 3D models from 3D-ultrasonic data is a complicated task due to the noisy, fuzzy nature of ultrasound imaging containing a lot of artifacts, speckle etc. In the method presented in this paper we first apply s...
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ISBN:
(纸本)9780897917018
Rendering 3D models from 3D-ultrasonic data is a complicated task due to the noisy, fuzzy nature of ultrasound imaging containing a lot of artifacts, speckle etc. In the method presented in this paper we first apply several filtering techniques (low-pass, mathematical morphology, multi-resolution analysis) to separate the areas of low coherency containing mostly noise and speckle from those of useful information. Our novel BLTP filtering can be applied at interactive times on-the-fly under user control & feed-back. Goal of this processing is to create a 'region-of-interest' (ROI) mask, whereas the data itself remains unaltered. Secondly, we examine several alternatives to the original Levoy contouring method. Finally we introduce an improved surface-extraction volume rendering procedure, applied on the original data within the ROI areas for visualizing high quality images within a few seconds on a normal workstation, or even on a PC, thus making the complete system suitable for routine clinical applications.
A method is presented to broaded implicit surface modeling. The implicit surfaces usually employed in computergraphics are two dimensional manifolds because they are defined by real-valued functions that impose a bin...
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ISBN:
(纸本)9780897917018
A method is presented to broaded implicit surface modeling. The implicit surfaces usually employed in computergraphics are two dimensional manifolds because they are defined by real-valued functions that impose a binary regionalization of space (i.e., an inside and an outside). When tiled, these surfaces yield edges of degree two. The new method allows the definition of implicit surfaces with boundaries (i.e., edges of degree one) and intersections (i.e., edges of degree three or more). These non-manifold implicit surfaces are defined by a multiple regionalization of space. The definition includes a list of those pairs of regions whose separating surface is of interest. Also presented is an implementation that converts a non-manifold implicit surface definition into a collection of polygons. Although following conventional implicit surface polygonization, there are significant differences that are described in detail. Several example surfaces are defined and polygonized.
We present actively procedural multiresolution paint textures. Texture elements may be linearly combined to create complex composite textures that continue to refine themselves when viewed at successively greater magn...
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We present actively procedural multiresolution paint textures. Texture elements may be linearly combined to create complex composite textures that continue to refine themselves when viewed at successively greater magnification. Actively procedural textures constitute a powerful drawing tool that can be used in a multiresolution paint system. They provide a mechanism to generate an infinite amount of detail with a simple and compact representation. We give several examples of procedural textures and show how to create different painting effects with them.
This paper describes a method for synthesizing images that match the texture appearance of a given digitized sample. This synthesis is completely automatic and requires only the 'target' texture as input. It a...
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ISBN:
(纸本)9780897917018
This paper describes a method for synthesizing images that match the texture appearance of a given digitized sample. This synthesis is completely automatic and requires only the 'target' texture as input. It allows generation of as much texture as desired so that any object can be covered. It can be used to produce solid textures for creating textured 3-d objects without the distortions inherent in texture mapping. It can also be used to synthesize texture mixtures, images that look a bit like each of several digitized samples. The approach is based on a model of human texture perception, and has potential to be a practically useful tool for graphics applications.
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