Abstract This paper describes Menv, an environment for the development of interactive three‐dimensional modelling and animation systems. Menv supports both interactive and procedural techniques. Systems built upon Menv are implemented as a set of independent, co‐operating tools operating upon a shared workspace. Models are defined in a high‐level procedural language with calls to graphical primitives. Animation data is bound to the model through the use of time‐varying articulated variables.

We present a solution to the aliasing problem for shadow algorithms that use depth maps. The solution is based on a new filtering technique called percentage closer filtering. In addition to antialiasing, the improved algorithm provides soft shadow boundaries that resemble penumbrae. We describe the new algorithm in detail, demonstrate the effects of its parameters, and analyze its performance.

Detail enhances the visual richness and realism of computer-generated images. Our stochastic modelling approach, called particle systems, builds complex pictures from sets of simple, volume-filling primitives. For example, structured particle systems have been used to generate trees and a grass-covered forest floor. Particle systems can produce so much irregular, three-dimensional detail that exact shading and visible surface calculations become infeasible. We describe approximate and probabilistic algorithms for shading and the visible surface problem. Because particle systems algorithms generate richly-detailed images, it is hard to detect any deviation from an exact rendering. Recent work in stochastic modelling also enables us to model complex motions with random variation, such as a field of grass blowing in the breeze. We analyze the performance of our current algorithms to understand the costs of our stochastic modelling approach.

This panel will discuss the issues and the problems associated with the simulation of natural phenomena. This is a difficult area of research since it generally involves complex data bases and in many instances time variant phenomena. The computational loads can become enormous as one considers the physics or the mathematical modeling of structures.

article Free Access Share on Particle systems—a technique for modeling a class of fuzzy objects Author: William T. Reeves Lucasfilm Ltd Lucasfilm LtdView Profile Authors Info & Claims ACM SIGGRAPH Computer GraphicsVolume 17Issue 3July 1983 pp 359–375https://doi.org/10.1145/964967.801167Published:01 July 1983Publication History 456citation4,113DownloadsMetricsTotal Citations456Total Downloads4,113Last 12 Months51Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

This paper introduces particle systems--a method for modeling fuzzy objects such as fire, clouds, and water.Particle systems model an object as a cloud of primitive particles that define its volume.Over a period of time, particles are generated into the system, move and change form within the system, and die from the system.The resulting model is able to represent motion, changes of form, and dynamics that are not possible with classical surface-based representations.The particles can easily be motion blurred, and therefore do not exhibit temporal aliasing or strobing.Stochastic processes are used to generate and control the many particles within a particle system.The application of particle systems to the wall of fire element from the Genesis Demo sequence of the film Star Trek H: The Wrath of Khan [10] is presented.

Motion analysis is the systematic and usually quantitative study of the movements of humans, animals, organisms, cells, or other entities as recorded on movie film or video tape. Despite the utility of computer-aided motion analysis to many biological, social, and physical sciences, its role has been limited because it is so time-consuming and so expensive. Automated techniques can only be used on real images in very special cases; interactive techniques have involved laborious frame by frame operations.In recent years, Futrelle and Potel have revolutionized the process of interactive motion analysis by demonstrating how to digitize entire motions with a single sketch rather than with a sequence of operations on each constituent frame. However, their GALA-TEA system is applicable only to film and not to video tape records, and consists of equipment which cannot easily be engineered into a reliable and mass-producible laboratory instrument.The paper describes a prototype laboratory instrument for the interactive motion analysis of video tape records. The prototype includes a host PDP 11/45 computer, an experimental display processor called SPIWRIT, and a microprocessor-controlled video disk. SPIWRIT generates a computer-animated video representation of the phenomenon being analysed, and superimposes it on the actual video record being streamed from the video disk. SPIWRIT's bit-slice microprogrammable display processor produces true animation on a colour raster display by decoding segmented display file images into alternate halves of a double frame buffer.

This paper presents an approach to computerized inbetweening which allows the animator more control over an interpolation sequence than existing keyframe techniques. In our approach, the animator specifies in addition to a set of keyframe constraints, a set of new constraints called moving points. Moving points are curves in space and time which constrain both the trajectory and dynamics of certain points on the keyframes. The sets of keyframes and moving points form a constraint or patch network specification of the desired dynamics. Several algorithms are presented for inbetweening or completing such a patch network. By measuring these algorithms with respect to a set of evaluation criteria, the algorithm which best meets our interpolation needs is selected.