A ray is a line segment that extends from a point in space in a specified direction. Rays have a number of uses in Unity but the most common is probably raycasting. This technique involves tracing along the path of a ray from its origin to determine if it intersects with any objects. This is useful for plotting the paths of projectiles, determining lines of sight and implementing many common game mechanics.See Also: Physics2D.Raycast, Ray class, RaycastHit2D class.