1. 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

2. 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
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3. 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
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4. 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.
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Real-Time Game Physics
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5. 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
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6. 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
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7. 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