Automatic addition of physics components to procedural content

While the field of procedural content generation is growing, there has been somewhat less work on developing procedural methods to animate these models. We present a technique for generating procedural models of trees and buildings via formal grammars (L-Systems and wall grammars) that are ready to be animated using physical simulation. The grammars and their interpretations are augmented to provide direct control over the physical animation, by, for example, specifying object mass and the joint stiffness. Example animations produced by our system include trees swaying in a gentle wind or being rocked by a gale, and buildings collapsing, imploding or exploding. In user testing, we had test subjects (n = 20) compare our animations with video of trees and buildings undergoing similar effects, as well as with animations in games that they have played. Results show that our animations appear physically accurate with a few minor instances of unrealistic behaviour. Users considered the animations to be more realistic than those used in current video games.