Wayne E. Carlson

Shape transformation for polyhedral objects

Techniques that transform one two-dimensionaf image into another have gained widespread use m recent yeara. Extending these techniques to transform pairs of 3D objects, as opposed to 2D images of the objects, providea several advsntagea, including the ability to snimate the objects independently of the transformation. This paper presents an algorithm for computing such transformations. The algorithm merges the topological structures of a pair of 3D polyhedral models into a common vertex/edgeJface network. This allows trsmsformations from one object to the other to be easily computed by interpolating between corresponding v@ex positions.

Anatomy-based modeling of the human musculature

Artists study anatomy to understand the relationship between exterior form and the structures responsible for creating it. In this paper we follow a similar approach in developing anatomy-based models of muscles. We consider the influence of the musculature on surface form and develop muscle models which react automatically to changes in the posture of an underlying articulated skeleton. The models are implemented in a procedural language that provides convenient facilities for defining and manipulating articulated models. To illustrate their operation, the models are applied to the torso and arm of a human figure. However, they are sufficiently general to be applied in other contexts where articulated skeletons provide the basis of modeling. CR

Simulating the structure and dynamics of human hair: Modelling, rendering and animation

We develop and present a new approach to modelling the characteristics of human hair, considering not only its structure, but also the control of its motion and a technique for rendering it in a realistic form. The approach includes a system for interactively defining the global positioning of the strands of hair on the head. Special attention is paid to the self shadowing of the hair. A mass/spring/hinge system is used to control a single strands position and orientation. We demonstrate that this approach results in a believable rendition of the hair and its dynamics.

Towards an interactive high visual complexity animation system

A computer animation system is discussed which employs interactive techniques and presents a unified approach to the graphical display of complex three dimensional data. The system facilitates the generation, manipulation and display of highly detailed data with the aid of interactive devices and a video interface to a standard color TV monitor. The system enables the animator to create a variety of objects (including texture) and to specify the necessary transformations for animation sequences. A run length processing technique combined with a brute force Z-buffer algorithm has been newly designed and implemented that can handle the intersection of several million faces, lines and points. This makes possible a full range of visual cues to simulate fire, smoke, water and complex 3-D texture such as grass, hair and bark. Basic concepts and approaches are described. The display algorithm and the procedure model to generate texture are presented and the implications of the system for computer animation are discussed. Extensions to the system are outlined which include a unique graphics display processor currently under construction that includes a partial implementation of the display algorithm in hardware.

An algorithm and data structure for 3D object synthesis using surface patch intersections

There are several successful systems that provide algorithms that allow for the intersection of polygonal objects or other primitive shapes to create more complex objects. Our intent is to provide similar algorithms for intersecting surface patches. There have been contributions to this concept at the display algorithm level, that is, computing the intersection at the time the frame is generated. In an animation environment, however, it becomes important to incorporate the intersection in the data generation routines, in order that those parts of the intersected object that never contribute to an image are not processed by the display algorithm. This only increases the complexity of the object unnecessarily, and subsequently puts an additional burden on the display algorithms. An algorithm is described which uses a modified Catmull recursive subdivision scheme to find the space curve which is the intersection of two bicubic patches. An associated data structure is discussed which incorporates this curve of intersection in the patch description in a way suitable for efficient display of the intersected object. Sample output of these intersections are shown which serve to illustrate the capabilities and limitations of the described procedures.

Solid spaces and inverse particle systems for controlling the animation of gases and fluids

This paper describes a new system for controlling the animation of gases, liquids, and volume density functions. This system is extremely powerful and flexible. It allows for the control of animation effects ranging from physically based motion of gases to the choreographed motion of gases. These techniques make extensive use of three-dimensional tables, including both flow vectors and motion functions for controlling gas animation. This new system uses aninverse particle system, where each point in three-dimensional screen space (image space discretized to pixel locations) is moved through a gas space to determine which portion of the gas occupies the current location in screen space.

Procedure models for generating three-dimensional terrain

A method for generating arbitrary terrain models, including trees, bushes, mountains, and buildings, is described. Procedure models are used to combine fundamental data elements in the creation of unified objects comprising the terrain model. As an example, a procedure model to generate arbitrary trees of various species is implementation. These are the generation of the low level data elements, specification of input parameter requirements, and a brief explanation of the algorithmic structure. Terrain images rendered by this process are included, as are diagrams and illustrations explaining the procedure model organization. Comparisons with previous work are made.

The determination of environmental accessibility and ada compliance through virtual wheelchair simulation

The widespread use of power wheelchairs has greatly increased the requirements for the accessibility of buildings and other architectural structures to handicapped persons. In addition, recent advances in microcomputer technology have made possible increasingly sophisticated power wheelchair interfaces, such as halo, puff and sip, and muscle control mechanisms, which can provide mobility for an even larger portion of the handicapped population. Finally, the ADA (the Americans with Disabilities Act of 1990) requires handicapped accessibility for (almost) all public structures. We have developed a virtual structure prototyping system that allows navigation by a person using a power wheelchair. The system is a tool for three groups of people: (1) for architects and designers, it provides structure visualization that can both improve the handicapped accessibility of building designs and test a structure for ADA compliance; (2) for wheelchair users, it provides more appropriate device fitting and training with wheelchair control mechanisms; and (3) for health care professionals, it provides evaluations of wheelchair users. The system consists of an instrumented, joystick-driven power wheelchair connected to a high-performance graphics workstation; it simulates the actual speed and maneuverability of the particular wheelchair within a virtual structure. The display generates realistic interiors containing multiple light sources and surface textures and is viewed in stereo through lightweight polarized glasses. The system maintains a hierarchical data structure which detects collisions between the virtual wheelchair and the environment. In this paper we discuss (1) the systems user interface, (2) the systems hardware and software configuration, (3) the impact of the system on the architectural design process, and (4) future system additions. In the last section we also discuss virtual manipulation for enabling technology.

A survey of computer graphics image encoding and storage formats

This paper is a survey of several storage formats used for computer generated or sampled images, both for purposes of archival storage and transmission (transfer from one location or platform to another). Various methodologies for the compression of such images are presented and discussed, Image storage standards and some of the more common commercial image storage techniques are presented in terms of the underlying compression algorithms they are based upon and the general internal data structures and formats.

3D volume visualization in remote radiation treatment planning

This paper reports a novel applications of 3D visualization in an ARPA-funded remote radiation treatment planning (RTP) experiment, utilizing supercomputer 3D volumetric modeling power and NASA ACTS (Advanced Communication Technology Satellite) communication bandwidths at the Ka-band range. The objective of radiation treatment is to deliver a tumorcidal dose of radiation to a tumor volume while minimizing doses to surrounding normal tissues. High performance graphics computers are required to allow physicians to view a 3D anatomy, specify proposed radiation beams, and evaluate the dose distribution around the tumor. Supercomputing power is needed to compute and even optimize dose distribution according to pre-specified requirements. High speed communications offer possibilities for sharing scarce and expensive computing resources (e.g., hardware, software, personnel, etc.) as well as medical expertise for 3D treatment planning among hospitals. This paper provides initial technical insights into the feasibility of such resource sharing. The overall deployment of the RTP experiment, visualization procedures, and parallel volume rendering in support of remote interactive 3D volume visualization will be described.