Integration of simulation tools in online virtual worlds Stéphane SIKORA AI Lab of Paris5 University 2nd conference on virtual worlds 5 July 2000

Simulation tools and virtual worlds Online virtual worlds are generally inhabited by avatars.  Use of simulation tools in order to enhance these virtual worlds (physics, biology).  Creation of autonomous entities (artificial life)  Possibility to play around the original simulation - Definition of a genotype for these entities - Use of genetic operators

2nd Garden Project 2 goals : –Computer simulation of growth process. Our model of plant is based on maize. –Use of this tool for a Virtual World application, leading to the development of a virtual garden. This project was inspired by Nerve Garden (Bruce Damer). This project is the result of a collaboration : S. Sikora, D. Steinberg, C. Lattaud (LIAP5) B. Andrieu, C. Fournier (INRA Grignon) F. Lediberder, S. Maguet (Canal numedia)

Plant development model Generally, modeling the growth process of plants (at the level of organs) requires: –A model of the activity of the apex (the organ responsible for the initiation of new organs) –A model of the other organs activity –An architectural model of the plant, describing its geometric structure. –A model of the environment A phytomer and its components.

L-systems Most widely used model of plant development (Lindenmayer, Prusinkievicz) Rewriting rules operating on strings of symbols. –Axiom: F –Rule: F  F[+F][-F]F Example of a graphical interpretation : F : Move Forward + - : Rotations of PI/3 [ ] : Encloses a sub tree

2 nd garden: plant model Model based on a multi agent system: -1 organ = 1 agent. Each organ has its own behavior - Synchronous simulation : 1 iteration = 1 simulated day) -Communication capabilities (endogenous flows) -Local response to environmental conditions

Effect of temperature Sensibility to the environment: Effect of temperature Plants sharing the same genotype Continuous growing temperature field (from left to right) Temperature has an effect on the speed of growth, the shape and the size of plants.

Genetic factors Each plant is defined by a genotype composed of 50 genes. The genes affect the organs behavior. Implementation of genetic operators (crossover, mutation) to explore the plants space.

Gene #17 Gene #17: amount of leaves and buds by phytomer Direct effect of this gene on phenotype.

Gene #28 Gene #28: maximum speed of growth of leaves Indirect effect of this gene on inter-nodes size

An evolution operator: crossover 10 different plants generated from the same parents. This offspring is the result of a crossover operator applied on the two parents.

A new world... The 2nd World (2W) : –Virtual community developed by Canal numedia. –Famous places of Paris reconstructed in VRML

Greenhouses in the 2nd World Each greenhouse has its own environmental conditions (temperature, moisture, enlightenment...). 6 times a day, a step of the growth process is performed. Users will have the opportunity to grow their own created seeds

Interactive construction of virtual seeds. Modification of the genes by use of genetic operators Visualization of the growth process PlanteStudio

PlanteStudio

Conclusion Original approach where the organs of plants are defined by agents. Everything done with L-systems can be done with this model.As biological models evolve quickly, the simulation has to be easy to maintain. With multi agent system, this is more straightforward and intuitive Coherent local response to the environment The communication between organs is easier to handle.

Future work Improvement of the biological model: –architectural model (roots) –internal communication –resource consumption Interaction between plants and users: –modification of environmental conditions –resource control –on line experimental laboratory