Animation is the process of rapidly displaying images to create the illusion of movement. Early animation devices like the zoetrope and praxinoscope were novelties for entertainment. Computer animation uses digital techniques like 2D bitmap and vector graphics to manipulate images. 3D animation adds depth by modeling objects with length, width and height that can be manipulated using rigging and other techniques. Popular software tools are used to create 2D and 3D animations for movies, TV and online content.