Browsing by Author "Liang, Xikun"

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    ANIMATING THE ESCAPE RESPONSE OF STOMPHIA COCCINEA FROM DERMASTERIAS IMBRICATA MODELED USING IMPLICIT SURFACES
    (2001-02-02) Nur, Mai; Liang, Xikun; Wyvill, Brian; Bourne, George
    Many 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.
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    A GENERAL FRAMEWORK FOR IMPLICIT MODELING
    (2002-03-15) Liang, Xikun; Wyvill, Brian
    A new implicit modeling method is introduced which represents a complex object as a hierarchy of implicit surfaces, in which each level is constrained by its parent. The method can be used in a variety of applications in modeling and animation. Novel aspects of the method are its ability to progressively refine the model, to create complex implicit objects through the composition of blending, controlled blending, CSG Boolean operations, and precise contact modeling, and to change the overall shape of the model while maintaining the integrity of the object. Most implicit modeling techniques build models that are collections of globally defined primitives or hierarchies in which each level is unconstrained by its parent. Our method builds a hierarchy of implicit surfaces progressively as new local details are introduced. As in H-Splines, local details are added to constrained areas and maintained during large scale shape changes. The method is well suited for both interactive and procedural implicit modeling. In addition, we describe a new methodology for the composition of implicit surfaces. We illustrate the intuitiveness and effectiveness of the new method in a number of examples of biological and engineering modeling and animation.
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    Hierarchical implicit surface refinement
    (2002) Liang, Xikun; Wyvill, Brian
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    HIERARCHICAL MODELING OF BLOB TREE WITH PRIMITIVE BASED LOCAL REFINEMENT
    (2000-12-06) Liang, Xikun; Wyvill, Brian
    This paper presents a novel method for implicit modeling of Blob Tree. Instead of modeling the implicit surface with shape transformations, refinement of the polygonization mesh or implicit particles, we introduce a method which builds a dynamic hierarchy of implicit surfaces and directly manipulates the surfaces and primitives. Based on the implicit primitives, the model is gradually refined by introducing appropriate new primitives at the specified surface areas. Refinement constraints such as local area and level of primitive hierarchy are designed to be applied on the implicit surfaces so as to achieve finer control over the local surface. The method can be used not only in modeling complex implicit objects, but also in animating the implicit surfaces and simulating the deformations of various objects.
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    MODELING THE STRUCTURE OF THE SEA ANEMONE, STOMPHIA COCCINEA AND THE SEA STAR, DERMASTERIAS IMBRICATA USING IMPLICIT SURFACES
    (2000-12-05) Liang, Xikun; Nur, Mai; Wyvill, Brian
    The Blob Tree provides a hierarchical data structure for the definition of complex models built from implicit surfaces, CSG Boolean operations and space warping functions. The implicit model within the system is defined as a hierarchical composition of multiple objects. In this paper, we describe an application of the Blob Tree to create visually accurate models of two invertebrates, the sea anemone, Stomphia Coccinea, and the sea star, Dermasterias Imbricata. The sea star was created using a variety of parameters that could be modified to create different variations of the Dermasterias Imbricata species. We use the phyllotactic method to obtain an accurate and visually pleasing arrangement of the sea anemone's tentacles. Using a hierarchical construction of the model, we can refine the model locally and deform it globally while maintaining the integrity of surface details. Taking advantage of the hierarchical representation of the object, we can easily adjust the model by simply changing some parameters of the surface or by performing global deformations on the anemone or local refinements on the tentacles.