UBC Theses and Dissertations

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UBC Theses and Dissertations

Design and optimization of control primitives for simulated characters Shen, Shuo


Physics-based character motion has the potential of achieving realistic motions without laborious work from artists and without needing to use motion capture data. It has potential applications in film, games and humanoid robotics. However, designing a controller for physics motions is a difficult task. It requires expertise in software engineering and understanding of control methods. Researchers typically develop their own dedicated software framework and invent their own sets of control rules to control physics-based characters. This creates an impediment to the non-expert who wants to create interesting motions and others who want to share and revise motions. In this thesis, we demonstrate that a set of motion primitives that have been developed in recent years constitute effective building blocks for authoring physics-based character motions. These motion primitives are made accessible using an expressive and flexible motion scripting language. The motion language allows a motion designer to create controllers in a text file that can be loaded at runtime. This is intended to simplify motion design, debugging, understanding and sharing. We use this framework to create several interesting 2D planar motions. An optimization framework is integrated that allows the hand-designed motion controller to be optimized for more interesting behaviors, such as a fast prone-to-standing motion. We also develop a state-action compatibility model for adaping controllers to new situations. The state-action compatibility model maintains a hypervolume of compatible states (“situations”) and actions (controllers). It allows queries for compatible actions given a state.

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