Animation of deformable models

Although kinematic modelling methods are adequate for describing the shapes of static objects, they are insufficient when it comes to producing realistic animation. Physically based modelling remedies this problem by including forces, masses, strain energies and other physical quantities. The paper describes a system for the animation of deformable models. The system uses physically based modelling methods and approaches from elasticity theory for animating the models. Two different formulations, namely the primal formulation and the hybrid formulation, are implemented so that the user can select the one most suitable for an animation depending on the rigidity of the models. Collision of the models with impenetrable obstacles and constraining of the model points to fixed positions in space are implemented for use in the animations. © 1994

A spring force formulation for elastically deformable models

Cataloged from PDF version of article.Continuous deformable models are generally represented using a grid of control points. The elastic properties are then modeled using the interactions between these points. The formulations based on elasticity theory express these interactions using stiffness matrices. These matrices store the elastic properties of the models and they should be evolved in time according to changing elastic properties of the models. However, forming the stiffness matrices at any step of an animation is very difficult and sometimes the differential equations that should be solved to produce animation become ill-conditioned. Instead of modeling the elasticities using stiffness matrices, the interactions between model points could be expressed in terms of external spring forces. In this paper, a spring force formulation for animating elastically deformable models is presented. In this formulation, elastic properties of the materials are represented as external spring forces as opposed to forming complicated stiffness matrices. (C) 1997 Elsevier Science Ltd

Fast generation of 3D deformable moving surfaces

Dynamic surface modeling is an important subject of geometric modeling due to their extensive applications in engineering design, entertainment and medical visualization. Many deformable objects in the real world are dynamic objects as their shapes change over time. Traditional geometric modeling methods are mainly concerned with static problems, therefore unsuitable for the representation of dynamic objects. Apart from the definition of a dynamic modeling problem, another key issue is how to solve the problem. Because of the complexity of the representations, currently the finite element method or finite difference method is usually used. Their major shortcoming is the excessive computational cost, hence not ideal for applications requiring real-time performance. We propose a representation of dynamic surface modeling with a set of fourth order dynamic partial differential equations (PDEs). To solve these dynamic PDEs accurately and efficiently, we also develop an effective resolution method. This method is further extended to achieve local deformation and produce n-sided patches. It is demonstrated that this new method is almost as fast and accurate as the analytical closed form resolution method and much more efficient and accurate than the numerical methods

Implicit Representations of the Human Intestines for Surgery Simulation

International audienceIn this paper, we propose a modeling of the intestines by implicit surfaces for abdominal surgery simulation. The difficulty of such a simulation comes from the animation of the intestines. As a matter of fact, the intestines are a very long tube that is not isotropically elastic, and that bends over itself at various spots, creating multiple self-contacts. We use a multiple component model for the intestines: The first component is a mechanical model of their axis; the second component is a specific sphere-based model to manage collisions and self-collisions; and the third component is a skinning model to define their volume. This paper focuses on the better representation for skinning the intestines. We compare two implicit models: Surfaces defined by point-skeletons and convolution surfaces. A direct application of this simulation is the training of a typical surgical gesture to move apart the intestines in order to reach certain areas of the abdomen

Physically-based animation of elastically deformable models

Ankara : Depatment of Computer Engineering and Information Science and Institute of Engineering and Science, Bilkent Univ., 1994.Thesis (Ph.D.) -- Bilkent University, 1994.Includes bibliographical references leaves66-71Although kinematic modeling methods are adequate for describing the shapes of static objects, they are insufficient when it comes to producing realistic animation. Physically-based modeling remedies this problem by including forces, masses, strain energies, and other physical quantities. The behavior of physicallybased models is governed by the laws of rigid and nonrigid dynamics expressed through a set of equations of motion. In this thesis, we describe a system for the animation of deformable models. A spring force formulation for animating deformable models is also presented. The animation system uses the physicallybased modeling methods and the approaches from elasticity theory for animating the models. Three different formulations, namely the primal, hrjhrid, and the spring force formulations, are implemented so that the user could select the suitable one for an animation, considering the advantages and disadvantages of each formulation. Collision of the models with impenetrable obstacles and constraining model points to fixed positions iii space are implemented.Güdükbay, UğurPh.D

Developing a virtual reality environment for petrous bone surgery: a state-of-the-art review

The increasing power of computers has led to the development of sophisticated systems that aim to immerse the user in a virtual environment. The benefits of this type of approach to the training of physicians and surgeons are immediately apparent. Unfortunately the implementation of “virtual reality” (VR) surgical simulators has been restricted by both cost and technical limitations. The few successful systems use standardized scenarios, often derived from typical clinical data, to allow the rehearsal of procedures. In reality we would choose a system that allows us not only to practice typical cases but also to enter our own patient data and use it to define the virtual environment. In effect we want to re-write the scenario every time we use the environment and to ensure that its behavior exactly duplicates the behavior of the real tissue. If this can be achieved then VR systems can be used not only to train surgeons but also to rehearse individual procedures where variations in anatomy or pathology present specific surgical problems. The European Union has recently funded a multinational 3-year project (IERAPSI, Integrated Environment for Rehearsal and Planning of Surgical Interventions) to produce a virtual reality system for surgical training and for rehearsing individual procedures. Building the IERAPSI system will bring together a wide range of experts and combine the latest technologies to produce a true, patient specific virtual reality surgical simulator for petrous/temporal bone procedures. This article presents a review of the “state of the art” technologies currently available to construct a system of this type and an overview of the functionality and specifications such a system requires

Incorporación de fuerzas de presión al modelado de cuerpos blandos

Se presenta un sistema de manejo de objetos flexibles 3D basado en leyes físicas, con fin de realizar diversas técnicas de modelado interactivo, a partir de una interfaz 2D. Se utiliza como motor un sistema de Mass-Spring-Damper extendido, con la incorporación de una fuerza interna adicional para representar el comportamiento de objetos de materiales blandos; el modelado puede desenvolverse ya sea aplicando fuerzas externas como controlando la interna, este método es lo suficientemente simple para dar buenos resultados en tiempos interactivosIII Workshop de Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI

Incorporación de fuerzas de presión al modelado de cuerpos blandos

Se presenta un sistema de manejo de objetos flexibles 3D basado en leyes físicas, con fin de realizar diversas técnicas de modelado interactivo, a partir de una interfaz 2D. Se utiliza como motor un sistema de Mass-Spring-Damper extendido, con la incorporación de una fuerza interna adicional para representar el comportamiento de objetos de materiales blandos; el modelado puede desenvolverse ya sea aplicando fuerzas externas como controlando la interna, este método es lo suficientemente simple para dar buenos resultados en tiempos interactivosIII Workshop de Computación Gráfica, Imágenes y Visualización (WCGIV)Red de Universidades con Carreras en Informática (RedUNCI