Showing papers by "John Keyser published in 2006"

Simultaneous shape decomposition and skeletonization

Abstract: Shape decomposition and skeletonization share many common properties and applications. However, they are generally treated as independent computations. In this paper, we propose an iterative approach that simultaneously generates a hierarchical shape decomposition and a corresponding set of multi-resolution skeletons. In our method, a skeleton of a model is extracted from the components of its decomposition --- that is, both processes and the qualities of their results are interdependent. In particular, if the quality of the extracted skeleton does not meet some user specified criteria, then the model is decomposed into finer components and a new skeleton is extracted from these components. The process of simultaneous shape decomposition and skeletonization iterates until the quality of the skeleton becomes satisfactory. We provide evidence that the proposed framework is efficient and robust under perturbation and. deformation. We also demonstrate that our results can readily be used in problems including skeletal deformations and virtual reality navigation.

Visualization of Fibrous and Thread-like Data

Abstract: Thread-like structures are becoming more common in modern volumetric data sets as our ability to image vascular and neural tissue at higher resolutions improves. The thread-like structures of neurons and micro-vessels pose a unique problem in visualization since they tend to be densely packed in small volumes of tissue. This makes it difficult for an observer to interpret useful patterns from the data or trace individual fibers. In this paper we describe several methods for dealing with large amounts of thread-like data, such as data sets collected using knife-edge scanning microscopy (KESM) and serial block-face scanning electron microscopy (SBF-SEM). These methods allow us to collect volumetric data from embedded samples of whole-brain tissue. The neuronal and microvascular data that we acquire consists of thin, branching structures extending over very large regions. Traditional visualization schemes are not sufficient to make sense of the large, dense, complex structures encountered. In this paper, we address three methods to allow a user to explore a fiber network effectively. We describe interactive techniques for rendering large sets of neurons using self-orienting surfaces implemented on the GPU. We also present techniques for rendering fiber networks in a way that provides useful information about flow and orientation. Third, a global illumination framework is used to create high-quality visualizations that emphasize the underlying fiber structure. Implementation details, performance, and advantages and disadvantages of each approach are discussed

Bending burning matches and crumpling burning paper

Abstract: In this work, we present a freeform deformation guided by physically based processes to model bending of objects when burning. Specifically, we can simulate the bending of burning matches, and the folding of burning paper interactively.

Exact polynomial system solving for robust geometric computation

Abstract: I describe an exact method for computing roots of a system of multivariate polynomials with rational coefficients, called the rational univariate reduction. This method enables performance of exact algebraic computation of coordinates of the roots of polynomials. In computational geometry, curves, surfaces and points are described as polynomials and their intersections. Thus, exact computation of the roots of polynomials allows the development and implementation of robust geometric algorithms. I describe applications in robust geometric modeling. In particular, I show a new method, called numerical perturbation scheme, that can be used successfully to detect and handle degenerate configurations appearing in boundary evaluation problems. I develop a derandomized version of the algorithm for computing the rational univariate reduction for a square system of multivariate polynomials and a new algorithm for a non-square system. I show how to perform exact computation over algebraic points obtained by the rational univariate reduction. I give a formal description of numerical perturbation scheme and its implementation.

Interactive face-replacements for modeling detailed shapes

Abstract: In this paper, we present a method that allows novice users to interactively create partially self-similar manifold surfaces without relying on shape grammars or fractal methods. Moreover, the surfaces created using our method are connected. The modelers that are based on traditional fractal methods or shape grammars usually create disconnected surfaces and restrict the creative freedom of users. In most cases, the shapes are defined by hard-coded schemes that provide only a few parameters that can be adjusted by the users. We present a new approach for modeling such shapes. With this approach, novice users can interactively create a variety of unusual and interesting partially self-similar manifold surfaces.

Particle-based enhancement of terrain data

Abstract: In this work, we discuss a particle-based method for eroding terrain data. We describe a method using particles to simulate rainfall effects, the flow of water, erosion and deposition, and formation of lakes and bodies of water.

Interactive Rule-Based Design - An experimental interface for conceptual design

Abstract: In this paper, we present a method that allows designers to interactively create partially self-similar manifold surfaces without relying on shape grammars or fractal methods. The modellers that are based on traditional fractal methods or shape grammars usually create disconnected surfaces and restrict the creative freedom of users. In most cases, the shapes through conventional fractal or shape grammar methods are defined by hard coded schemes that allow limited interactivity for the design process. We present a new approach for modelling such shapes. With this approach, we have developed a simple generative tool with given adjustable parameters to achieve variety of conceptual forms. Using this tool, designers can interactively create a variety of partially self-similar manifold surfaces.