Browsing by Author "Wyvill, Brian"
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- ItemOpen AccessA framework for rule based behavioural simulation in voxel space(1996) Zhang, Hongwen; Wyvill, Brian
- ItemOpen AccessADAPTIVE VOXEL SUBDIVISION FOR RAY TRACING(1988-11-01) Jevans, David; Wyvill, BrianAlthough regular subdivision has been shown to be efficient at ray tracing scenes where objects are evenly distributed, such algorithms perform poorly when objects are concentrated in a small number of voxels. In this paper, a method is presented where voxels in a regular grid are examined and recursively subdivided depending on object density. This integration of regular and adaptive spatial subdivision methods allows images consisting of large regularly distributed objects and small dense objects to be ray traced efficiently. The parameters controlling the coarseness of the voxel grid, depth of adaptive subdivision trees, and maximum number of polygons per voxel are varied and their effects on execution time, subdivision time, and memory use are measured.
- ItemOpen AccessAn Integrated kernel for computer animation(1990) Chmilar, Michael; Wyvill, Brian
- ItemOpen AccessAnimating implicit surfaces(2002) Nur, Mai Ali; Wyvill, Brian
- ItemOpen AccessANIMATING SPEECH: AN AUTOMATED APPROACH .brUSING SPEECH SYNTHESISED BY RULES(1987-08-01) Hill, David. R.; Pearce, Andrew; Wyvill, BrianThis paper is concerned with the problem of animating computer drawn images of speaking human characters, and particularly with the problem of reducing the cost of adequate lip synchronisation. Since the method is based upon the use of speech synthesis by rules, extended to manipulate facial parameters, and there is also a need to gather generalised data about facial expressions associated with speech, these problems are touched upon as well. Useful parallels can be drawn between the problems of speech synthesis and those of facial expression synthesis. The paper outlines the background to the work, as well as the problems and some approaches to solution, and goes on to describe work in progress in the authors' laboratories that has resulted in one apparently successful approach to low-cost animated speaking faces. Outstanding problems are noted, the chief ones being the difficulty of selecting and controlling appropriate facial expression categories; the lack of naturalness of the synthetic speech; and the need to consider the body movements and speech of all characters in an animated sequence during the animation process.
- ItemOpen AccessANIMATING THE ESCAPE RESPONSE OF STOMPHIA COCCINEA FROM DERMASTERIAS IMBRICATA MODELED USING IMPLICIT SURFACES(2001-02-02) Nur, Mai; Liang, Xikun; Wyvill, Brian; Bourne, GeorgeMany of the most interesting behaviors in the biological world have to do with interactions between species. The predator-prey interactions among aquatic organisms is an interesting part of the natural world which has not been seen much in computer animation. This paper explores the interaction between various sea anemones and the starfish Dermasterias imbricata. Although a simulation between a specific sea anemone, Stomphia coccinea to Dermasterias imbricata was created, an approach was taken such that different anemones can with minor parameter changes be used to replace S. coccinea. The animation was created using a parametric keyframe approach of procedural models. The anemone and starfish were modeled using the Blob Tree. The implicit model within the system is defined as a hierarchical composition of multiple objects. Using a hierarchical construction of the model, we can refine the model locally and deform it globally while maintaining the integrity of surface details.
- ItemOpen AccessANIMATION IN WARPED SPACE(1993-10-01) van Overveld, Kees; Wyvill, BrianFree form deformations are useful for describing a class of complex motions within an animation system. Such deformations have been described using a generalization of parametric surfaces and their application to modeling is well documented. In this paper we present a method that can be applied to implicit surfaces which are defined as an iso-surface around a set of skeletal elements, contributing to a scalar field. The resulting surface is approximated by a polygon mesh. Shape distortions, such as "squash and stretch" are applied automatically to models in motion by warping the space in which the models exist. A model will change its shape as the function defining the warped space can change over time or, the model will deform as it moves through the warped space. Sophisticated, possibly non-linear deformations can be achieved on arbitrarily complex surfaces. Several examples are given including a running wave simulation and a slug like creature. The interesting, non-linear motion obtained, from space warping would be difficult to reproduce using other techniques.
- ItemOpen AccessApplication of implicit methods to the interactive modeling of trees(2010) Kochhar, Vishal; Prusinkiewicz, Przemyslaw; Wyvill, Brian
- ItemOpen AccessBehavioural animation of monarch butterflies(2004) Dorosh, Shane Cory; Wyvill, BrianAn example of the behavioural animation of Monarch butterflies is presented. An attempt is made to demonstrate that realistic Monarch motion can be reproduced using a structurally valid behavioural model, i.e. a model based on the steering behaviour of real Monarchs. A three-dimensional simulation of Monarch flight is used, in which the role of wing-flapping in locomotion is prioritized. The position, orientation, and wing articulation of a number of Monarchs are advanced one step at a time to recreate the process of flight and thereby produce the animation. Changes in position are physically-based, i.e. the mathematics are based on a "particle" representation for each of the simulated Monarchs. The simulation terrain includes gravity, and the behavioural algorithms are physically grounded, meaning that they function in terms of literal features of Monarch flight. Realistic and robust behaviour is obtained with a compact set of routines.
- ItemOpen AccessBiomechanical joint motion synthesis(1995) Thorne, Christopher D.; Wyvill, Brian
- ItemOpen AccessBlob Tree Trees(2003-12-19) Galbraith, Callum; MacMurchy, Peter; Wyvill, BrianIn recent years several methods for modelling botanical trees have been proposed. The geometry and topology of tree skeletons can be well described by L-systems, however there are several approaches to modelling smooth surfaces to represent branches, and not all of the observed phenomena can be represented by current methods. Many tree types exhibit non-smooth features such as branch bark ridges and collars. In this paper we present a botanical tree modelling approach that uses a hierarchical implicit modelling system. The BlobTree provides several techniques to control the combination of primitives, and allows both smooth and non-smooth effects to be combined in a single blend volume in an easily controlled fashion. We use the BlobTree to produce models of botanical tree branching structures that capture smooth branching, branch collars and branch bark ridges in a single model. The BlobTree is used as a procedural surface modelling system, taking input from L-system botanical tree descriptions. We show that smooth, C1 continuous blends can be obtained without noticeable bulging, using summation blending. We implement irregular effects using Precise Contact Modelling, Constructive Solid Geometry and space warping.
- ItemOpen AccessTHE BLOB TREE- WARPING, BLENDING AND BOOLEAN OPERATIONS IN AN IMPLICIT SURFACE MODELING SYSTEM(1998-03-01) Wyvill, Brian; Guy, Andrew; Galin, EricAutomatic blending has characterized the major advantage of implicit surface modeling systems. Recently, the introduction of deformations based on space warping and boolean operations between primitives has increased the usefulness of such systems. We propose a further enhancement which will greatly enhance the range of models that can be easily and intuitively defined with a skeletal implicit surface system. We describe an hierarchical method which allows arbitrary compositions of models that make use of blending, warping and boolean operations. We call this structure the BlobTree. Blending and space warping are treated in the same way as union, difference and intersection, i.e. as nodes in the BlobTree. The traversal of the BlobTree is described along with two rendering algorithms; a polygonizer and a ray tracer. We present some examples of interesting models which can be made easily using our approach that would be very difficult to represent with conventional systems.
- ItemOpen AccessBlobtree modelling(2008) de Groot, Erwin P.H.; Wyvill, Brian
- ItemMetadata onlyBLOCKAID A MODEL FOR PROGRAM EXECUTION(1984-06-01) Birtwistle, Graham; Wyvill, BrianWe illustrate a technique for picturing the dynamic behaviour of block structured programs under execution. Examples are shown using Pascal programs but the method is perfectly general. It shows how procedures are incarnated when called and deleted on exit. A clear interpretation of the binding rule is given for local and global variables and parameters; and the need for multiple copies for recursively called procedures is demonstrated.
- ItemMetadata onlyA COLLECTION OF THREE COMPUTER SCIENCE PLAYS(1984-12-01) Wyvill, BrianThis document consists of the scripts from three plays presented as a Christmas entertainment for the Department of Computer Science. The plays are as follows: 1982 - Squanderella 1983 - Digital Alice 1984 - Twenty Eighty Four
- ItemOpen AccessCOLUMBUS(1991-03-01) Wyvill, Brian; Bramwell, BobMarch 1991
- ItemMetadata onlyCOMPUTER ANIMATION AT THE UNIVERSITY OF CALGARY(1984-04-01) Wyvill, Brian; Maulsby, David; McPheeters, CraigThe computer has been used as a tool to aid animation artists in a number of ways; from controlling rostrum cameras to producing complete animation sequences from three dimensional descriptions of real objects. This paper describes Graphicsland, a suite of programs developed to explore the medium of 3D animation. Graphicsland recognizes that there is no single "correct" approach to solving the problems of design, storage, movement, rendering and production of animated film and video. Instead a variety of techniques are offered and the design of the system is such that it may easily be extended to incorporate new algorithms and graphical databases in the future.
- ItemOpen AccessCONSTRUCTIVE SOFT GEOMETRY: THE UNIFICATIONS OF CSG AND IMPLICIT SURFACES(1995-04-01) Wyvill, Brian; van Overveld, KeesA solid modeling technique is proposed which combines some essential ideas from Constructive Solid Geometry and Implicit Surface Modeling based on soft objects. The result is a surface definition (to be called Boolean Compound Soft Object, or BCSO for short) which consists of a boolean expression with union, intersection and set difference operators. The geometric primitives that form the operands are soft objects bounded by the iso-surfaces resulting from suitable potential fields. These potential fields are parameterized by configurations of so called skeletal elements. The resulting system, unlike most CSG systems, combines blended and unblended primitives. An algorithm for the boundary of a BCSO is presented which produces a mesh of triangles to facilitate fast viewing and rendering.
- ItemOpen AccessCONTROLLED BLENDING OF PROCEDURAL IMPLICIT SURFACES(1990-12-01) Kacic-Alesic, Zoran; Wyvill, BrianImplicit surfaces are becoming increasingly popular for modeling geometric objects. Procedurally defined implicit surfaces, in particular surfaces built around skeletons, provide an intuitive representation for many natural objects, and objects commonly used in geometric modeling. This paper presents a number of techniques that provide good control over the shape of the implicit surface and the way different surfaces blend together. Some extensions to these techniques provide a simple and convenient representation for "soft" surfaces of revolution, randomly deformed surfaces, and other interesting shapes that would otherwise be difficult to model.
- ItemOpen AccessDeformation based modelling(1991) Haman, Anja; Wyvill, Brian