We present an algorithm for fast, physically accurate simulation of deformable objects suitable for real time animation and virtual environment interaction. We describe the boundary integral equation formulation of static linear elasticity as well as the related Boundary Element Method (BEM) discretization technique. In addition, we show how to exploit the coherence of typical interactions to achieve low latency; the boundary formulation lends itself well to a fast update method when a few boundary conditions change. The algorithms are described in detail with examples from ArtDefo, our implementation.

This paper presents a survey of the work done in modeling deformable objects within the computer graphics research community. The research has a long history and a wide variety of approaches have been used. This paper organizes the diversity of research by the technique used rather than by the application, although applications are discussed throughout. This paper presents some purely geometric approaches for modeling deformable objects, but focuses on physically based approaches. In the latter category are mass-spring models, nite element models, approximate continuum models, and low degree of freedom models. Special emphasis is placed on nite element models, which o er the greatest accuracy, but have seen limited use in computer graphics. The paper also suggests important areas for future research. 1

A system for simulating arthroscopic knee surgery that is based on volumetric object models derived from 3D Magnetic Resonance Imaging is presented. Feedback is provided to the user via real-time volume rendering and force feedback for haptic exploration. The system is the result of a unique collaboration between an industrial research laboratory, two major universities, and a leading research hospital. In this paper, components of the system are detailed and the current state of the integrated system is presented. Issues related to future research and plans for expanding the current system are discussed. Introduction Computer-based surgical simulation has many applications in education and training, surgical planning, and intra-operative assistance. Given the low availability and high cost of cadaver and animal specimens, surgical simulation can be used in medical education and training to reduce costs, to provide experience with a greater variety of pathologies and complications, and...

This paper describes a method for creating object surfaces from binary-segmented data that are free from aliasing and terracing artifacts.

. We present a new approach for the computation of the deformation field between three dimensional (3D) images. The deformation field locally minimizes the sum of the squared differences between the images to be matched and is constrained by the physical properties of the different objects represented by the image. The objects are modeled as elastic bodies. Compared to optical flow methods, this approach distinguishes itself by three main characteristics: it can account for the actual physical properties of the objects to be deformed, it can provide us with physical properties of the deformed objects (i.e. stress tensors), and computes a global solution to the deformation instead of a set of local solutions. This latter characteristic is achieved through a finite-element based scheme. The finite element approach requires the different objects in the images to be meshed. Therefore, a tetrahedral mesh generator using a pre-computed case table and specifically suited for segme...

We present a framework for the interactive simulation of surgical cuts such as being practiced in surgical treatment. Unlike most existing methods our framework is based on tetrahedral volume meshes providing more topological flexibility. In order to keep the representation consistent we apply adaptive subdivision schemes dynamically during the simulation. The detection of collisions between the surgical tool and the tissue is accomplished by using an axis aligned bounding box hierarchy which was adapted for deformable objects. For haptic rendering and feedback, we devised a mechanical scalpel model which accounts for the most important interaction forces between scalpel and tissue. The relaxation is computed using a localized, semi-implicit ODE solver. The achieved quality and performance of the presented framework is demonstrated using a human soft tissue model. 1 Introduction and Related Work Over the past years surgery simulation has emerged as an fascinating field of research of...

In this paper, we introduce the concept of spatial transfer functions as a unified approach to volume modeling and animation. A spatial transfer function is a function that defines the geometrical transformation of a scalar field in space, and is a generalization and abstraction of a variety of deformation methods. It facilitates a field-based representation, and can thus be embedded into a volumetric scene graph under the algebraic framework of constructive volume geometry. We show that when spatial transfer functions are treated as spatial objects, constructive operations and conventional transfer functions can be applied to such spatial objects. We demonstrate spatial transfer functions in action with the aid of a collection of examples in volume visualization, sweeping, deformation and animation. In association with these example, we describe methods for modeling and realizing spatial transfer functions, including simple procedural functions, operational decomposition of complex functions, large scale domain decomposition and temporal spatial transfer functions. We also discuss the implementation of spatial transfer functions in the vlib API and our efforts in deploying the technique in volume animation.

In this paper, we describe a technique to animate volumes using a volumetric skeleton. The skeleton is computed from the actual volume, based on a reversible thinning procedure using the distance transform. Polygons are never computed, and the entire process remains in the volume domain. The skeletal points are connected and arranged in a "skeleton-tree", which can be used for articulation in an animation program. The full volume object is regrown from the transformed skeletal points. Since the skeleton is an intuitive mechanism for animation, the animator deforms the skeleton and causes corresponding deformations in the volume object. The volumetric skeleton can also be used for volume morphing, automatic path navigation, volume smoothing and compression/decimation. Keywords:Volume Graphics, Skeleton, Animation, Volume Deformation. 1 Introduction The field of volume graphics is gaining momentum as volumetric datasets become more widespread and the computational power to render these...

Abstract The focus of this paper is the newly developed Enhanced ChainMail Algorithm that will be used for modeling the vitreous humor in the eye during surgical simulation. The simulator incorporates both visualization and biomechanical modeling of a vitrectomy, anintraocular surgical procedure for removing the vitreous humor. The Enhanced ChainMail algorithm extends the capabilities of an existing algorithm for modeling deformable tissue, 3D ChainMail, by enabling the modeling of inhomogeneous material. In this paper, we present the enhanced algorithm and demonstrate its capabilities in 2D.

Interactive surgery simulations have conflicting requirements of speed and accuracy. In this paper we show how to combine a relatively accurate deformation model---the Finite Element (FE) method---and interactive cutting without requiring expensive matrix updates or precomputation. Our approach uses an iterative algorithm for an interactive linear FE deformation simulation. The iterative process requires no global precomputation, so runtime changes of the mesh, i.e. cuts, can be simulated efficiently. Cuts are performed along faces of the mesh; this prevents growth of the mesh. We present a provably correct method for changing the mesh topology, and a satisfactory heuristic for determining along which faces to perform cuts. The incision surface will be jagged; this problem is a subject of current research. Keywords: finite elements, tissue deformation, simplicial complex, virtual surgery, tetrahedral mesh, cutting