Showing papers by "Charles R. Dyer published in 1993"

The scale space aspect graph

Abstract: Currently the aspect graph is computed from the theoretical standpoint of perfect resolution in object shape, the viewpoint and the projected image. This means that the aspect graph may include details that an observer could never see in practice. Introducing the notion of scale into the aspect graph framework provides a mechanism for selecting a level of detail that is "large enough" to merit explicit representation. This effectively allows control over the number of nodes retained in the aspect graph. This paper introduces the concept of the scale space aspect graph, defines three different interpretations of the scale dimension, and presents a detailed example for a simple class of objects, with scale defined in terms of the spatial extent of features in the image. >

Vision-guided exploration: a step toward general motion planning in three dimensions

Abstract: An approach to solving the path planning problem for a mobile robot operating in an unknown, three dimensional environment containing obstacles of arbitrary shape is presented. The main contributions are an analysis of the type of sensing information that is necessary and sufficient for solving the path planning problem in such environments, and the development of a framework for designing a provably correct algorithm to solve this problem. Working from first principles, without any assumptions about the environment of the robot or its sensing capabilities, the analysis shows that the ability to explore the obstacle surfaces (i.e., to make all their points visible) is intrinsically linked to the ability to plan the motion of the robot. It is argued that current approaches to the path planning problem with incomplete information simply do not extend to the general three-dimensional case, and that qualitatively different algorithms are needed. >

Computing spatiotemporal relations for dynamic perceptual organization

Abstract: To date, the overwhelming use of motion in computational vision has been to recover the three-dimensional structure of the scene. We propose that there are other, more powerful, uses for motion. Toward this end, we define dynamic perceptual organization as an extension of the traditional (static) perceptual organization approach. Just as static perceptual organization groups coherent features in an image, dynamic perceptual organization groups coherent motions through an image sequence. Using dynamic perceptual organization, we propose a new paradigm for motion understanding and show why it can be done independently of the recovery of scene structure and scene motion. The paradigm starts with a spatiotemporal cube of image data and organizes the paths of points so that interactions between the paths, and perceptual motions such as common , relative , and cyclic are made explicit. The results of this can then be used for high-level motion recognition tasks.

Dynamic shading, motion parallax and qualitative shape

Abstract: The authors address the problem of qualitative shape recovery from moving surfaces. The analysis is unique in that they consider specular interreflections and explore the effects of both motion parallax and changes in shading. To study this situation they define an image flow field called the reflection flow field, which describes the motion of reflection points and the motion of the surface. From a kinematic analysis, they show that the reflection flow is qualitatively different from the motion parallax because it is discontinuous at or near parabolic curves. They also show that when the gradient of the reflected image is strong, gradient-based flow measurement techniques approximate the reflection flow field and not the motion parallax. They conclude that reliable qualitative shape information is generally available only at discontinuities in the image flow field. >

The VIS-AD Data Model: Integrating Metadata and Polymorphic Display with a Scientific Programming Language

Abstract: The VIS-AD data model integrates metadata about the precision of values, including missing data indicators and the way that arrays sample continuous functions, with the data objects of a scientific programming language The data objects of this data model form a lattice, ordered by the precision with which they approximate mathematical objects We define a similar lattice of displays and study visualization processes as functions from data lattices to display lattices Such functions can be applied to visualize data objects of all data types and are thus polymorphic

Toward global surface reconstruction by purposive viewpoint adjustment

Abstract: The following problem is considered: how should an observer change viewpoint in order to generate a dense image sequence of an arbitrary smooth surface so that it can be incrementally reconstructed using the occluding contour and the epipolar parameterization? A collection of qualitative behaviors is presented that, when integrated appropriately, purposefully control viewpoint based on the appearance of the surface in order to provably solve this problem. >

Building global surface models by purposive and qualitative viewpoint adjustment

Abstract: We present an approach for recovering a global surface model of an object from the deformation of the occluding contour using an active (i.e., mobile) observer able to control its motion. In particular, we consider two problems: (1) How can the observer's viewpoint be controlled in order to generate a dense sequence of images that allows incremental reconstruction of an unknown surface? And (2) how can we construct a global surface model from the generated image sequence? We achieve the first goal by purposefully and qualitatively controlling the observer's instantaneous direction of motion in order to control the motion of the visible rim over the surface. We achieve the second goal by using a stationary calibrated trinocular camera rig and a mechanism for controlling the relative position and orientation of the viewed surface with respect to the trinocular rig. Unlike previous shape-from-motion approaches which derive quantitative shape information from an arbitrarily generated sequence of images, we develop a collection of simple and efficient viewing strategies that allow the observer to achieve the global reconstruction goal by maintaining specific geometric relationships with the viewed surface. These relationships depend only on tangent computations on the occluding contour. To demonstrate the feasibility and effectiveness of our approach we apply the developed algorithms to synthetic and real scenes.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.