An animator produces multiple images called frames, which when sequenced together create an illusion of movement known as animation. The images can be made up of digital or hand-drawn pictures, models or puppets. Animators tend to work in 2D animation, 3D model-making animation, stop frame or computer-generated animation. Computer-generated animation features strongly in motion pictures (to create special effects or an animated film in its own right), as well as in aspects of television, the internet and the computer games industry. The basic skill of animation still relies heavily on artistic ability, but there is an increasing need for animators to be familiar with technical computer packages.