Ideally, virtual worlds should be dynamic, mutable, and complex in order to be attractive for immersed users. As such worlds can be designed easily by rewriting techniques, we propose a distributed Virtual Reality (VR) system that is based on an interactive animation system using a rewriting technique for geometric and behavioral modeling. The emphasis is on concepts and extensions for the integration of user immersion, user interaction, and networking into a rewriting-based animation system, Finally, the modeling of a ball game with two immersed users, as well as a virtual park, serve as case studies to illustrate the proposed concepts and extensions.

Lworld is a computer graphics animation system based on L-systems, a parallel rewriting technique used primarily in computer graphics for plant modeling. Because rule-based programming is a powerful technique, we use it as a basis for a general-purpose animation system. We describe the architecture, the features, and the programming language of the animation system. It is particularly well suited to model fractal curves, plants, fractal landscapes, group animation, visualization, and evolutionary optimizations. Lworld allows users to create real-time animations as well as raytraced image sequences for further movie production. It is freely available, and runs on PCs.

In computer graphics L-systems represent a powerful rule-based language for modeling complex objects and their animation. However, designing objects and animations by rules is a difficult task because designers often cannot foresee the consequences of rules. This is especially true for non-experts in the domain. Therefore, we propose to enhance an L-system based animation system with evolutionary features based on genetic algorithms (GAs). These features support the designers' task of interactively modeling objects and animations. Starting from an initial population of L-system-defined objects, the computer proposes iteratively new populations based on fitness value that are determined by the designers' creative or functional criteria. Moreover, automatic optimization of L-system-defined objects/animations is possible if an appropriate fitness function can be found for a given problem. We present a concept to integrate optimization by genetic algorithms into an L-system based animation system. Typical examples, such as automatic function optimization and creative interactive design of objects, illustrate our work.

We present a versatile, behavioral, and rule-based animation system that includes autonomous humanoid actors whose behavior is based on synthetic sensors that are used for perceiving the virtual environment. We combine the following in a consistent approach: L-systems, a behavioral production rule system; a particle system; an acoustic environment model, including a speech recognition module; a virtual life network; and a humanoid library. Together, these systems create a real-time-structured virtual environment that both high-level autonomous humanoids and interactive users can easily share.

We propose a model of a tennis game simulation with synthetic actors as players and a referee. The behaviour of these actors is based on their synthetic vision and audition. Physical modeling of the ball dynamic and sound rendering enhance realism. An interactive user can also play against a synthetic actor by using a Space Ball.

We present a formal theory of a behavioral L-system and describe as application a real time structured L-system interpreter. The behavioral L-system is a timed, conditional, stochastic, parametric and environmentally sensitive L-system which allows besides the modeling of plant and fractal development the description and animation of autonomous actors completely defined by production rules. A virtual environment including geometric objects, force fields and sounds and the behaviors of actors can be defined using the same formalism of the behavioral L-systems.

Abstract We present an overview of some principles of synthetic vision and audition for digital autonomous actors in virtual worlds. After a short review of the state‐of‐the‐art we focus on some aspects of synthetic vision and virtual world constraints. Then, we present a simple real time structured sound renderer. This sound renderer is used as audition channel for synthetic and real actors and synchronized sound track generator for video film productions.

The scope of this paper is to propose a system for the automatic derivation of a human curved walking trajectory from the analysis provided by its synthetic vision module. The study context is a planar environment with still and sparse foothold locations. A general methodology associates the two low-level modules of vision and walking with a planification module which establishes the middle term path from the knowledge of the visualized environment. The planification is made under the constraint of minimizing the distance, the speed variation and the curvature cost. Moreover, the planification may trigger the alternate walking motion whenever the decreasing in curvature cost is higher than the associated increasing in speed variation cost due to the corresponding halt and restart. Finally, the characteristic of the next step location is derived in the context of a constant velocity walking motion along a circular trajectory.>