Rich Gossweiler

Perceiving geographical slant.

People judged the inclination of hills viewed either out-of-doors or in a computer-simulated virtual environment. Angle judgments were obtained by having people (1) provide verbal estimates, (2) adjust a representation of the hill’s cross-section, and (3) adjust a tilt board with their unseen hand. Geographical slant was greatly overestimated according to the first two measures, but not the third. Apparent slant judgments conformed to ratio scales, thereby enhancing sensitivity to the small inclines that must actually be traversed in everyday experience. It is proposed that the perceived exaggeration of geographical slant preserves the relationship between distal inclination and people’s behavioral potential. Hills are harder to traverse as people become tired; hence, apparent slant increased with fatigue. Visually guided actions must be accommodated to the actual distal properties of the environment; consequently, the tilt board adjustments did not reflect apparent slant overestimations, nor were they influenced by fatigue. Consistent with the fact that steep hills are more difficult to descend than to ascend, these hills appeared steeper when viewed from the top.

An introductory tutorial for developing multiuser virtual environments

This paper is an introductory level tutorial describing how to implement a distributed multiparticipant virtual environment (VE). This tutorial is intended for students who are competent programmers and who now wish to implement a distributed multiparticipant application. We describe the fundamental concepts of distributed computing for multiplayer simulations and provide a concrete example, including C source code available via the Internet. The template program demonstrates a simple multiplayer, distributed application, where each player controls the position of a space ship, and communicates the ships position data over the network. The template uses broadcast communication and a technique called dead-reckoning to improve performance. We give detailed instructions on how to obtain and modify the template, so that students can quickly create their own distributed applications. We conclude by briefly discussing advanced issues that are important when constructing more sophisticated multiparticipant VEs.

Alice: a rapid prototyping system for building virtual environments

Alice is a rapid prototyping system used to create three dimensional graphics simulations like those seen in virtual reality applications. Alice uses an interpreted language called Python to implement the semantics of user actions. This interactive development environment allows users to explore many more design options than is possible in a compiled language environment.

DIVER: A Distributed Virtual Environment Research platform

DIVER is the Virtual Environment software architecture library developed at the University of Virginia. It is similar to SGIs Inventor, but was developed specifically as a toolkit for creating Virtual Environments rather than for mouse-based applications. Like Inventor, DIVER was implemented on top of the SGIs GL library and provides a powerful hierarchical graphics database. Unlike Inventor, DIVER is distributed, divorcing the application computations from the rendering computations. DIVER runs the application on a remote CPU and transparently spawns asynchronous rendering processes onto one or more SGIs. DIVER extends the graphics database hierarchy by allowing programmers to perform graphics transformations in any other objects nested coordinate system, and by allowing the programmer to nest the virtual camera (viewpoint) anywhere in the hierarchy. DIVER has been active use for over a year by more than twenty researchers.<<ETX>>

Eviza: A Natural Language Interface for Visual Analysis

Natural language interfaces for visualizations have emerged as a promising new way of interacting with data and performing analytics. Many of these systems have fundamental limitations. Most return minimally interactive visualizations in response to queries and often require experts to perform modeling for a set of predicted user queries before the systems are effective. Eviza provides a natural language interface for an interactive query dialog with an existing visualization rather than starting from a blank sheet and asking closed-ended questions that return a single text answer or static visualization. The system employs a probabilistic grammar based approach with predefined rules that are dynamically updated based on the data from the visualization, as opposed to computationally intensive deep learning or knowledge based approaches. The result of an interaction is a change to the view (e.g., filtering, navigation, selection) providing graphical answers and ambiguity widgets to handle ambiguous queries and system defaults. There is also rich domain awareness of time, space, and quantitative reasoning built in, and linking into existing knowledge bases for additional semantics. Eviza also supports pragmatics and exploring multi-modal interactions to help enhance the expressiveness of how users can ask questions about their data during the flow of visual analysis.

Amortizing 3D graphics optimization across multiple frames

Abstract : This paper describes a mechanism for improving rendering rates dynamically during runtime in an interactive three-dimensional graphics application. Well-known techniques such as transforming hierarchical geometry into a flat list and removing redundant graphics primitives are often performed off-line on static databases, or continuously every rendering frame. In addition, these optimizations are usually performed over the whole database. We observe that much of the database remains static for a fixed period of time, while other portions are modified continuously (e.g. the camera position), or are repeatedly modified during some finite interval (e.g. during user interaction). We have implemented a runtime optimization mechanism which is sensitive to repeated, local database changes. This mechanism employs timing strategies which optimize only when the cost of optimization will be amortized over a sufficient number of frames. Using this optimization scheme, we observe a rendering speedup of roughly 2.5 in existing applications. We discuss our initial implementation of this mechanism, the improved timing measurements, the issues and assumptions we made, and future improvements.

Alice and DIVER: a software architecture for building environments

We are developing a rapid prototyping system built on an objeet-onented, interpreted language which allows small interdisciplinary teams to quickly create and modify threedimensional interactive simulations. Like other systems, we separate the simulation and presentation frame rates, but unlike existing systems, we do so in such a way that the application-level programmer need not understand the multi-process architecture. The system has been used for building perceptual psychology experiments, for replicating techniques developed by other researchers, and for experimenting with novel three-dimensional interaction techniques.