Game Design, Development, and Technology CS 382 Game Design, Development, and Technology Real-Time Game Physics Domain-Specific Dynamics Rigid Body Dynamics Continuum Dynamics Ragdoll Physics Game Engines Part 4.3

Real-Time Game Physics One Goal in Games: Physical Reality (Within Reason) To maximize the player’s immersion in a game, it’s important to model the physics of the game environment as accurately as possible. Even abstract games that don’t simulate the “real” world (e.g., Tetris) have their own physics model that makes gameplay understandable. Some of the desirable physics features that should be modeled in games: Gravity Collisions Friction Fluid dynamics Part 4.3 Real-Time Game Physics Page 127

Real-Time Game Physics Physics Topic: Domain-Specific Dynamics Customized physics engines that accommodate specific simulated environments (e.g., flight simulators) can focus on that environment’s physical constraints, rather than modeling all of reality. Example: Car Simulators Desirable modeling: Torque Suspension Skid Marks Tire Heating Wheel constraints Fuel consumption Road Conditions Part 4.3 Real-Time Game Physics Page 128

Real-Time Game Physics Physics Topic: Rigid-Body Dynamics Solid objects are the most common type of objects in a game (they’re easiest to model). It’s important to render their animation accurately, taking into account mass, momentum, friction, and elasticity. Part 4.3 Real-Time Game Physics Page 129

Real-Time Game Physics Physics Topic: Continuum Dynamics Draping Cloth Constrained Chain Clothing in Motion Elastic Blob Fluid Surface Part 4.3 Real-Time Game Physics Page 130

Real-Time Game Physics Physics Topic: Ragdoll Physics When a dying character is collapsing to the ground, the bones of its skeletal system are tied together by a system of constraints that restrict how they move relative to each other, adding more realism to the appearance. Verlet Integration Each bone is modeled as a simple point connected to an arbitrary number of other points via simple constraints. Inverse Kinematics Post-Processing A preset death animation is played, followed by the application of IK to force the character into a valid position. Blended Ragdoll A premade animation is played, but its output is constrained to what a physical system would allow, eliminating the character’s sudden limpness, but reducing processing speed. Part 4.3 Real-Time Game Physics Page 131

Real-Time Game Physics Physics Engines for Games While commercial and open source physics engines facilitate the incorporation of physics features into games, developers still need a basic understanding of the physics in order to properly use the engines. Part 4.3 Real-Time Game Physics Page 132