Group simulation
The group simulation (English: crowd simulation) describes the simulation of the behavior of a large number of objects or figures / people. In 3D computer animation , group simulation has been increasingly used since the film Lord of the Rings at the latest , since conventional animation techniques - in which each figure is animated individually - are too complex (and therefore too expensive) in mass scenes.
functionality
A crowd scene consists of numerous similar characters. Movement libraries are created for these figures that contain all possible movements of the figure or its “body” parts. The movement libraries are either created individually or can be procedurally created automatically on the basis of known movement schemes or biological principles.
The actual movements of the characters and the interaction between the characters can be simulated in two ways:
- Particle animation
- The figures are subordinated to a particle system , which in turn simulates wind, gravity , attraction and / or repulsion. This type of simulation is relatively easy to do - appropriate particle systems are available for most 3D modeling tools . However, this type of group simulation is not particularly realistic, as you have little influence on the individual movements of the characters. An example of this type of animation is swimming down a waterfall in empty barrels: the figures in the barrels can be animated (rowing their arms, screaming for help) - but the barrels themselves obey strictly physical laws when traveling over the waterfall ( Gravity, drifting against each other, bouncing off rocks).
- Group AI
- Each figure - in this case also called an agent - is provided with a certain artificial intelligence that controls the behavior of the figure based on (simulated) vision, hearing, feelings, power reserves, aggressiveness, etc. In addition, each figure is given a goal. The interaction of the characters is then simulated based on the goals and characteristics, so that a very realistic group behavior is created. Usually the characters are programmed to react to changes in their (simulated) environment and thus, for example, circumvent obstacles, climb hills, jump over holes, kill simulated enemies, etc. The standard example for animation with group AI is two enemy armies short before the battle. The rules for each character in this example are quite simple: kill as many enemies as possible, avoid killing friends, try to stay alive yourself.
The group AI generates much more realistic results, but is very complex to implement and has so far mostly been programmed individually for an animation project. With the software package Massive or Softimage Behavior developed for Weta Digital , commercial products are available that make group simulation accessible to a larger group of users.
Other areas of application
A related application is the planning of buildings and places with heavy public traffic in order to simulate the behavior of people during an evacuation and to incorporate structural measures into the design. Such evacuation simulations use findings from group dynamics and group psychology . The focus here is less on the visualization, but more on the behavior itself. The basic technology here is also the group AI, but with more complex rule sets.