David Meyers

Surfaces from contours

This paper is concerned with the problem of reconstructing the surfaces of three-dimensional objects, given a collection of planar contours representing cross-sections through the objects. This problem has important aplications in biomedical research and instruction, solid modeling, and industrial inspection. The method we describe produces a triangulated mesh from the data points of the contours which is then used in conjunction with a piecewise parametric surface-fitting algorithm to produce a reconstructed surface. The problem can be broken into four subproblems: the correspondence problem (which contours should be connected by the surface?), the tiling problem (how should the contours be connected?), the branching problem (what do we do when there are branches in the surface?), and the surface-fitting problem (what is the precise geometry of the reconstructed surface?) We describe our system for surface reconstruction from sets of contours with respect to each of these subproblems. Special attention is given to the correspondence and branching problems. We present a method that can handle sets of contours in which adjacent contours share a very contorted boundary, and we describe a new approach to solving the correspondence problem using a Minimum Spanning Tree generated from the contours.

Computer methods for sampling, reconstruction, display and analysis of retinal whole mounts

We are quantifying the distribution of photoreceptors and ganglion cells in human retina with the goal of establishing a reliable anatomical database which may be compared to information about visual function. We required a representation of retinal cell distributions which facilitated collection, analysis, and display of morphometric data from the entire retina of a large number of eyes. We report computer methods to (1) reconstruct the original retinal sphere from a three-piece whole mount preparation; (2) sample the retina in a manner which allowed description of approximately radially symmetrical cell distributions and avoided both undersampling (which produces interpolation artifacts) and oversampling (which wastes time); (3) interpolate between data points in order to produce plots of cell density along arbitrary meridians and maps of average cell density from several eyes; (4) specify locations on the retinal surface using a spherical coordinate system with its primary axis through the fovea; and (5) produce color-coded maps of cell distributions in a standard perimetric projection.

A Structured Approach to Developing Real-Time, Distributed Network Applications for ITS Deployment∗

This paper describes a structured approach to developing ITS applications which are instantiated as real-time, distributed computing applications that are suitable for distributing dynamic data in real time to a large but authorized group of users. The approach is based on an asynchronous, distributed, client/server architecture and relies on the creation of autonomous, reusable pieces of software. Within this approach, applications are seen not as clients, but rather as configurations of the various structured software components. The paper first presents the general development framework and then demonstrates the approach by describing several applications that have been created and deployed in the domain of Intelligent Transportation System. The paradigms presented here fit within the context of the FHWA ITS Architecture.

A self-describing data transfer model for ITS applications

The wide variety of remote sensors used in Intelligent Transportation Systems (ITS) applications (loops, probe vehicles, radar, cameras, etc.) has created a need for general methods by which data can be shared among agencies and users who own disparate computer systems. In this paper, we present a methodology that demonstrates that it is possible to create, encode, and decode a self-describing data stream using: 1) existing data description language standards; 2) parsers to enforce language compliance; 3) a simple content language that flows out of the data description language; and 4) architecture neutral encoders and decoders based on ASN.1.

Testbed for the comparison of parametric surface methods

There are currently a number of methods for solving variants of the following problem: Given a triangulated polyhedron P in three-space with or without boundary, construct a smooth surface that interpolates the vertices of P. Problems of this variety arise in numerous areas of application such as medical imaging, scattered data fitting, and geometric modeling. In general, while the techniques satisfy the continuity and interpolation requirements of the problem, they often fail to produce pleasing shapes. Our interest in studying this problem has necessitated the construction of a flexible software testbed that allows rapid implementation and testing of new surface fitting methods and analysis techniques. The testbed is written entirely in the C programming language and is highly portable. Other relevant features of the testbed are discussed, and recommendations for improving the shape characteristics of several interpolation methods are given.

A statistical model for dynamic ridematching on the World Wide Web

Seattle Smart Traveler (SST) is an application of World Wide Web (WWW) technology to test the concept of automated dynamic ride-share matching. This paper reports a new statistical model for quantifying ride-share matching and car pooling. The model is validated using the SST experimental results, and the model demonstrates that the car-pooling process is a quadratic function of the number of users participating.