Collision detection typically refers to the computational problem of detecting the intersection of two or more objects. While the topic is most often associated with its use in video games and other computer simulations|physical simulations, it also has applications in robotics. In addition to determining whether two objects have collided, collision detection systems may also calculate time of impact (TOI), and report a contact manifold (the set of intersecting points). Collision response deals with simulating what happens when a collision is detected (see physics engine, ragdoll physics). Solving collision detection problems requires extensive use of concepts from linear algebra and computational geometry.