ABSTRACT
Collision detection is a very broad topic, relevant to computer games and toother applications such as navigation and robotics. The classic example for collision detection in a third-person perspective, indoor game is having the main character move around in a set of rooms that contain obstacles. The character is controlled by an input device, typically a joystick, keyboard, or mouse, and must not be allowed to walk through the walls or obstacles. Moreover, if the character walks into a wall, he might be allowed to slide along the wall in a direction that is oblique to the one implied by the event from the input device. A standard technique for preventing the character from walking through a wall is to enclose the character with a tight-fitting bounding volume and test whether it intersects the plane of the wall. The collision detection system must provide support for this test even when the character (and its bounding volume) is moving. Preventing the character from walking through an obstacle is as simple as enclosing the obstacle with its own bounding volume and testing for intersection between the character and obstacle bounding volumes. Other typical situations in a game that require collision detection are keeping vehicles moving over a terrain without dropping through it, monitoring racing cars on a track and detecting when two cars hit or when a car hits a wall, determining when a projectile hits an intended target, bouncing objects off other objects, providing feedback about character control when two characters are fighting, and determining if an object can pass through an opening, such as when a character attempts to walk through a doorway that may or may not be tall enough.
