Jeremy D. Wendt

IMPaSTo: a realistic, interactive model for paint

We present a paint model for use in interactive painting systems that captures a wide range of styles similar to oils or acrylics. The model includes both a numerical simulation to recreate the physical flow of paint and an optical model to mimic the paint appearance.Our physical model for paint is based on a conservative advection scheme that simulates the basic dynamics of paint, augmented with heuristics that model the remaining key properties needed for painting. We allow one active wet layer, and an unlimited number of dry layers, with each layer being represented as a height-field.We represent paintings in terms of paint pigments rather than RGB colors, allowing us to relight paintings under any full-spectrum illuminant. We also incorporate an interactive implementation of the Kubelka-Munk diffuse reflectance model, and use a novel eight-component color space for greater color accuracy.We have integrated our paint model into a prototype painting system, with both our physical simulation and rendering algorithms running as fragment programs on the graphics hardware. The system demonstrates the models effectiveness in rendering a variety of painting styles from semi-transparent glazes, to scumbling, to thick impasto.

LLCM-WIP: Low-Latency, Continuous-Motion Walking-in-Place

Walking-in-place techniques for locomotion in virtual environments typically have two problems that impact their usability: system latency (particularly troublesome when starting and stopping locomotion), and the fact that the change in the users viewpoint may not be smooth and continuous. This paper describes a new WIP interface that improves both latency and the continuity of synthesized locomotion in the virtual environment. By basing the virtual avatar motion on the speed of the users heel motion while walking in place, we create a direct mapping from foot-motion to locomotion that is responsive, intuitive, and easy to implement. In this paper, we describe the technique, analyze its starting and stopping latency, and provide experimental results on the suppression of false steps and general usability of the system.

GUD WIP: Gait-Understanding-Driven Walking-In-Place

Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model — called Gait-Understanding-Driven Walking-In-Place (GUD WIP) — creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system — Low-Latency, Continuous-Motion (LLCM) WIP — while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency — LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

Finite volume flow simulations on arbitrary domains

We present a novel method for solving the incompressible Navier-Stokes equations that more accurately handles arbitrary boundary conditions and sharp geometric features in the fluid domain. It uses a space filling tetrahedral mesh, which can be created using many well-known methods, to represent the fluid domain. Examples of the methods strengths are illustrated by free surface fluid simulations and smoke simulations of flows around objects with complex geometry.

CC shadow volumes

We present a technique that uses culling and clamping (CC) for accelerating the performance of stencil-based shadow volume computation. Our algorithm reduces the fill requirements and rasterization cost of shadow volumes by reducing unnecessary rendering. A culling step removes shadow volumes that are themselves in shadow or do not contribute to thefinal image. Our novel clamping algorithms restrict shadow volumes to those regions actually containing shadow receivers. In this way, we avoid rasterizing shadow volumes over large regions of empty space. We utilize temporal coherence between successive frames to speed up clamping computations. Even with fairly coarse clamping we obtain substantial reduction in fill requirements and shadow rendering time in dynamic environments composed of up to a 100K triangles.

Physically based virtual painting

Tapping the compelling illusion of physical interaction with paints, brushes, surfaces, color, and light, users express the nuances of their visual and emotional imaginations.

Lessons about virtual environment software systems from 20 years of ve building

What are desirable and undesirable features of virtual environment (VE) software architectures? What should be present (and absent) from such systems if they are to be optimally useful? How should they be structured? In order to help answer these questions, we present experience from application designers, toolkit designers, and VE system architects along with examples of useful features from existing systems. Topics are organized under the major headings of 3D space management, supporting display hardware, interaction, event management, time management, computation, portability, and the observation that less can be better. Lessons learned are presented as discussion of the issues, field experiences, nuggets of knowledge, and case studies.