This paper discusses collision detection and response in computer animation. It presents two collision detection algorithms: one for flexible or rigid surfaces and another for convex polyhedra. The first algorithm tests for interpenetration of surfaces by checking if any vertex point passes through a triangle. The second algorithm tests for interpenetration of convex polyhedra by checking if edges intersect with faces. Both algorithms are simple, robust, and efficient. For collision response, the paper presents two methods: one using temporary springs and another using an analytical solution. The spring method is intuitive and works for both rigid and flexible bodies, but is computationally expensive. The analytical method is faster and conserves linear and angular momentum, making it suitable for realistic simulations. The paper also describes how to handle collisions between dynamic and non-dynamic objects, where the non-dynamic objects' velocities are fixed. The paper concludes that collision detection is essential for realistic animation. While naive approaches can be computationally expensive, efficient techniques like bounding boxes and octrees can reduce the cost. Dynamical simulation systems must resolve collisions after detection, and the choice between spring and analytical methods depends on the situation. A combination of both methods is recommended for optimal results.This paper discusses collision detection and response in computer animation. It presents two collision detection algorithms: one for flexible or rigid surfaces and another for convex polyhedra. The first algorithm tests for interpenetration of surfaces by checking if any vertex point passes through a triangle. The second algorithm tests for interpenetration of convex polyhedra by checking if edges intersect with faces. Both algorithms are simple, robust, and efficient. For collision response, the paper presents two methods: one using temporary springs and another using an analytical solution. The spring method is intuitive and works for both rigid and flexible bodies, but is computationally expensive. The analytical method is faster and conserves linear and angular momentum, making it suitable for realistic simulations. The paper also describes how to handle collisions between dynamic and non-dynamic objects, where the non-dynamic objects' velocities are fixed. The paper concludes that collision detection is essential for realistic animation. While naive approaches can be computationally expensive, efficient techniques like bounding boxes and octrees can reduce the cost. Dynamical simulation systems must resolve collisions after detection, and the choice between spring and analytical methods depends on the situation. A combination of both methods is recommended for optimal results.