Browsing by Author "van Overveld, Kees"

Now showing 1 - 3 of 3
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    ANIMATION IN WARPED SPACE
    (1993-10-01) van Overveld, Kees; Wyvill, Brian
    Free 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.
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    CONSTRUCTIVE SOFT GEOMETRY: THE UNIFICATIONS OF CSG AND IMPLICIT SURFACES
    (1995-04-01) Wyvill, Brian; van Overveld, Kees
    A 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.
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    Visualizing Batik
    (2003-01-28) Wyvill, Brian; van Overveld, Kees; Carpendale, Sheelagh
    We present an algorithm for simulating the Batik wax painting and dyeing technique used to make images on cloth. The algorithm produces cracks similar to those found in Batik due to the wax cracking in the dyeing process. The method is unlike earlier simulation techniques used in computer graphics, in that it is based on the Distance Transform algorithm rather than on a physically based simulation such as using spring mass meshes or finite element methods. Such methods can be difficult to implement and computationally costly due to large numbers of equations that need to be solved. In contrast, our method is simple to implement and takes only a few seconds to produce convincing patterns that capture many of the characteristics of the crack patterns found in real Batik cloth.