Daniel Thalmann

Biomechanical Models for Soft Tissue Simulation

An overview of biomechanical modeling of human soft tissue using nonlinear theoretical mechanics and incremental finite element methods, useful for computer simulation of the human musculoskeletal system.

Nonverbal communication interface for collaborative virtual environments

Nonverbal communication is an important aspect of real-life face-to-face interaction and one of the most efficient ways to convey emotions, therefore users should be provided the means to replicate it in the virtual world. Because articulated embodiments are well suited to provide body communication in virtual environments, this paper first reviews some of the advantages and disadvantages of complex embodiments. After a brief introduction to nonverbal communication theories, we present our solution, taking into account the practical limitations of input devices and social science aspects. We introduce our sample of actions and implementation using our VLNET (Virtual Life Network) networked virtual environment and discuss the results of an informal evaluation experiment.

Virtual humans: thirty years of research, what next?

In this paper, we present research results and future challenges in creating realistic and believable Virtual Humans. To realize these modeling goals, real-time realistic representation is essential, but we also need interactive and perceptive Virtual Humans to populate the Virtual Worlds. Three levels of modeling should be considered to create these believable Virtual Humans: 1) realistic appearance modeling, 2) realistic, smooth and flexible motion modeling, and 3) realistic high-level behaviors modeling. At first, the issues of creating virtual humans with better skeleton and realistic deformable bodies are illustrated. To give a level of believable behavior, challenges are laid on generating on the fly flexible motion and complex behaviours of Virtual Humans inside their environments using a realistic perception of the environment. Interactivity and group behaviours are also important parameters to create believable Virtual Humans which have challenges in creating believable relationship between real and virtual humans based on emotion and personality, and simulating realistic and believable behaviors of groups and crowds. Finally, issues in generating realistic virtual clothed and haired people are presented.

The benefits of third-person perspective in virtual and augmented reality?

Instead of the reality in which you can see your own limbs, in virtual reality simulations it is sometimes disturbing not to be able to see your own body. It seems to create an issue in the proprio-perception of the user who does not completely feel integrated in the environment. This perspective should be beneficial for the users. We propose to give the possibility to the people to use the first and the third-person perspective like in video games (e.g. GTA). As the gamers prefer to use the third-person perspective for moving actions and the first-person view for the thin operations, we will verify this comportment is extendable to simulations in augmented and virtual reality.

A biomechanical musculoskeletal model of human upper limb for dynamic simulation

In this paper, we provide the biomechanical model of human upper limb we have designed and applied to the three-dimensional left human arm reconstructed from the visible human imaging dataset. This model includes the mechanical properties for bones, joints and muscles lines of action. This work has been done as a part of the European Esprit Project CHARM. Its objective is to develop a comprehensive human animation resource model allowing the dynamic simulation of complex musculoskeletal systems, including finite element deformation of soft-tissues and muscular contraction. In our approach, simplifications have been done so as to ensure the feasibility of the project while preserving the biomechanical validity of the model.

An object-oriented methodology using dynamic variables for animation and scientific visualization

An object-oriented design is presented for building dynamic three-dimensional applications. This design takes the form of the Fifth Dimension Toolkit consisting of a set of interrelated classes whose instances may be connected together in a variety of ways to form different applications. Animation is obtained by connecting graphical objects to dynamic variables, which are able to change their values over time by responding to events. The Fifth Dimension Toolkit is the core of the Fifth Dimension Project, a research project for animating synthetic actors in their environment. The design philosophy and methodology of the toolkit are also described, as well as some of the implementation issues for the Silicon Graphics Iris 4D workstation.

Creating Realistic Three-Dimensional Human Shape Characters for Computer-Generated Films

In this paper, we discuss both the artistic and technical concerns involved in the construction of a computergenerated realistic human character. We investigate various methods for creating three-dimensional human shapes based on our experiences. The traditional approach consists in constructing the shapes from real human characters or plaster models. In the first part, we survey several methods that we have already used in the past: 3D reconstruction from 2D photos, 3D digitizing using a Polhemus digitizer, cross sections method and local deformations. Then, we show how a direct sculpting approach based on threedimensional devices like the spaceball or the dataglove could considerably improve the situation. We have obtained a realistic human character with a method similar to the modelling of clay, work which essentially consists of adding or eliminating parts of the material, and turning around the object when the principal form has been set up.

Stable real-time interaction between virtual humans and real scenes

We present an augmented reality system that relies on purely passive techniques to solve the real-time registration problem. It can run on a portable PC and does not require engineering of the environment, for example by adding markers. To achieve this result, we have integrated robust computer vision techniques into a powerful VR framework. The resulting AR system allows us to produce complex rendering and animation of virtual human characters, and to blend them into the real world. The system tracks the 3D camera position by means of a natural features tracker, which, given a rough CAD model, can deal with complex 3D objects. The tracking method can handle both large camera displacements and aspect changes. We will show that our system works in the cluttered environment of a real industrial facility and can, therefore, be used to enhance manufacturing and industrial processes.

The mobile animator: interactive character animation in collaborative virtual environments

We have designed a mobile -PDA-based- interface for real-time control of virtual characters in multiuser semi-immersive virtual environments - using a large rear-projection screen. The proof-of-concept implementation we present shows the potential of handheld devices as powerful interfaces to virtual reality applications. This technique eliminates the display of floating menus and other widgets over the simulation screen. A brief discussion on the advantages and disadvantages of using a handheld for 3D interaction is presented as well

Deformable Surfaces using Physically Based Particle Systems

Publisher Summary This chapter discusses a method for animating deformable surfaces using physically based particle systems. The use of physically based models for animating deformable surfaces is an important field in computer graphics. There are two successful approaches to this problem: particle systems and continuous systems. Particle systems consist of a large number of single particles, all of which move under the influence of the forces, such as gravity and external forces, etc. The particle systems were originally used to model fire, fireworks, waterfall, ocean, spray, trees, grass and other natural phenomena. More recently, particle systems have been used to model deformable surfaces. An interesting work in this area is the description of cloth draping behavior. In this field, the interacting-particle methods have been used to develop a theoretical model of woven cloth and predicate the drape of woven cloth such as cotton and wool. This chapter proposes the use of particle systems and a series of simple methods for creating and animating a deformable surface which has a similar result to continuous systems, but with better stability and much faster speed of calculation. The shape of the surfaces is easily controlled.