Arthur D. Gregory

Six degree-of-freedom haptic display of polygonal models

We present an algorithm for haptic display of moderately complex polygonal models with a six degree of freedom (DOF) force feedback device. We make use of incremental algorithms for contact determination between convex primitives. The resulting contact information is used for calculating the restoring forces and torques and thereby used to generate a sense of virtual touch. To speed up the computation, our approach exploits a combination of geometric locality, temporal coherence, and predictive methods to compute object-object contacts at kHz rates. The algorithm has been implemented and interfaced with a 6-DOF PHANToM Premium 1.5. We demonstrate its performance on force display of the mechanical interaction between moderately complex geometric structures that can be decomposed into convex primitives.

inTouch: interactive multiresolution modeling and 3D painting with a haptic interface

We present an intuitive 3D interface for interactively editing and painting a polygonal mesh using a force feedback device. An artist or a designer can use the system to create and refine a three-dimensional multiresolution polygonal mesh. Its appearance can be further enhanced by directly painting onto its surface. The system allows users to naturally create complex forms and patterns not only aided by visual feedback, but also by their sense of touch.

Interactive surface decomposition for polyhedral morphing

We present a new approach for establishing correspondence for morphing between two homeomorphic polyhedral models. The user can specify corresponding feature pairs on the polyhedra with a simple and intuitive interface. Based on these features, our algorithm decomposes the boundary of each polyhedron into the same number of morphing patches. A 2D mapping for each morphing patch is computed in order to merge the topologies of the polyhedra one patch at a time. We create a morph by defining morphing trajectories between the feature pairs and by interpolating them across the merged polyhedron. The user interface provides high-level control, as well as local refinement to improve the morph. The implementation has been applied to several polyhedra composed of thousands of polygons. The system can also handle homeomorphic non-simple polyhedra that are not genuszero (or have holes).

Feature-based surface decomposition for correspondence and morphing between polyhedra

Presents a new approach for establishing correspondence between two homeomorphic 3D polyhedral models. The user can specify corresponding feature pairs on the polyhedra with a simple and intuitive interface. Based on these features, our algorithm decomposes the boundary of each polyhedron into the same number of morphing patches. A 2D mapping for each morphing patch is computed in order to merge the topologies of the polyhedra one patch at a time. We create a morph by defining morphing trajectories between the feature pairs and by interpolating them across the merged polyhedron. The user interface provides high-level control as well as local refinement to improve the morph. The implementation has been applied to several complex polyhedra composed of thousands of polygons. The system can also handle non-simple polyhedra that have holes.

A framework for fast and accurate collision detection for haptic interaction

We present a framework for fast and accurate collision detection for haptic interaction with polygonal models. Given a model, we pre-compute a hybrid hierarchical representation, consisting of uniform grids and trees of tight-fitting oriented bounding box trees (OBB-Trees). At run time, we use hybrid hierarchical representations and exploit frame-to-frame coherence for fast proximity queries. We describe a new overlap test, which is specialized for intersection of a line segment with an oriented bounding box for haptic simulation and takes 6-36 operations excluding transformation costs. The algorithms have been implemented as part of H-COLLIDE and interfaced with a PHANToM arm and its haptic toolkit, GHOST, and applied to a number of models. As compared to the commercial implementation, we are able to achieve up to 20 times speedup in our experiments and sustain update rates over 1000 Hz on a 400 MHz Pentium II.

Fast and accurate collision detection for haptic interaction using a three degree-of-freedom force-feedback device

Abstract We present a fast and accurate collision detection algorithm for haptic interaction with polygonal models. Given a model, we precompute a hybrid hierarchical representation, consisting of uniform grids (represented using a hash table) and trees of tight-fitting oriented bounding box trees (OBBTrees). At run time, we use hybrid hierarchical representations and exploit frame-to-frame coherence for fast proximity queries. We describe a new overlap test, which is specialized for intersection of a line segment with an oriented bounding box for haptic simulation and takes 42–72 operations including transformation costs. The algorithms have been implemented as part of H-COLLIDE and interfaced with a PHANToM arm and its haptic toolkit, GHOST, and applied to a number of models. As compared to the commercial implementation, we are able to achieve up to 20 times speedup in our experiments and sustain update rates over 1000 Hz on a 400 MHz Pentium II. In practice, our prototype implementation can accurately and efficiently detect contacts between a virtual probe guided by a force-feedback arm and large complex geometries composed of tens of thousands of polygons, with substained KHz rates.

A touch‐enabled system for multi‐resolution modeling and 3D painting‡

We present an intuitive system, inTouch, for interactively editing and painting a polygonal mesh using a force-feedback device. An artist or a designer can use this system to create and refine a three-dimensional multi-resolution polygonal mesh. The appearance can be further enhanced by directly painting onto its surface. The system allows users to naturally create complex forms and patterns aided not only by visual feedback but also by their sense of touch. Copyright

Offset curve deformation from skeletal animation

Skin deformation based on an underlying skeleton is a critical part of the modern animation pipeline. Linear blend skinning is fast but suffers volume loss at a bend and “candy wrapper” pinching under twist. More complex methods using dual quaternions [Kavan et al. 2007] and bind-point offset from intermediate curves [Singh and Fiume 1998] are nearly as fast and reduce these artifacts, but dual quaternions are limited only to rigid transformations and bind-point techniques continue to suffer from offset distortion, which increases with distance from the bind point, causing uneven stretching and self-intersection on the inside of a bend when offsets exceed the radius of curvature.

Camera control in three dimensions with a two-dimensional input device

Abstract We implement a variety of operations to control a virtual camera using a two-dimensional modal input device, such as a standard three-button mouse. The operations offer control of position, orientation, zoom, and a separate scaling parameter for the view of the world. All operations are designed to be easy to use for the end user, but we also designed for ease of implementation for the programmer.