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David M. Chelberg

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3 papers

2 author rows

ICRA Conference 1987 Conference Paper

Finding the limbs and cusps of generalized cylinders

Jean Ponce
David M. Chelberg

This paper addresses the problem of finding analytically the limbs and cusps of generalized cylinders. Orthographic projections of generalized cylinders whose axis is straight and whose axis is an arbitrary 3D curve are considered in turn. In both cases, the general equations of the limbs and cusps are given. They are solved for three classes of generalized cylinders: solids of revolution, straight homogeneous generalized cylinders whose scaling sweeping rule is a polynomial of degree less than or equal to 5 and generalized cylinders whose axis is an arbitrary 3D curve but the cross section is circular and constant. Examples of limbs and cusps found for each class are given. Extensions and applications of the results presented are discussed.

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ICRA Conference 1987 Conference Paper

Localized intersections computation for solid modelling with straight homogenous generalized cylinders

Jean Ponce
David M. Chelberg

This paper reports progress in the development of a solid modelling system combining straight homogeneous generalized cylinders through set operations. Two basic components of this system are the modules which compute the set operations between primitives and display the resulting solids using ray tracing. These two modules are also very computationally intensive as they involve a large number of surface-surface and ray-surface intersections computations. We introduce a novel hierarchical representation for straight homogeneous cylinders called Box Tree. The Box Tree is analogous to a Quadtree in parameter space. It is an exact boundary representation which describes the surface of the associated generalized cylinder by a hierarchy of enclosing boxes. We use the Box Tree to efficiently compute the set operations and ray tracing algorithms by localizing the search for intersections to the regions where they may occur. We discuss complexity issues and illustrate the performances of our modelling system on a variety of examples.

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AAAI Conference 1987 Conference Paper

Qualitative Landmark-Based Path Planning and Following

Tod S. Levitt
David M. Chelberg

This paper develops a theory for path planning and following using visual landmark recognition for the representation of environmental locations. It encodes local perceptual knowledge in structures called viewframes and orientation regions. Rigorous representations of places as visual events are developed in a uniform framework that smoothly integrates a qualitative version of path planning with inference over traditional metric representations. Paths in the world are represented as sequences of sets of landmarks, viewframes, orientation boundary crossings, and other distinctive visual events. Approximate headings are computed between viewframes that have lines of sight to common landmarks. Orientation regions are range-free, topological descriptions of place that are rigorously abstracted from viewframes. They yield a coordinate-free model of visual landmark memory that can also be used for path planning and following. With this approach, a robot can opportunistically observe and execute visually cued "shortcuts".

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