To trick the visual system into seeing a smoothly moving object, the pictures should be drawn at around 12 frames per second or faster (a frame is one complete image). With rates above 75 to 120 frames per second, no improvement in realism or smoothness is perceivable due to the way the eye and the brain both process images. At rates below 12 frames per second, most people can detect jerkiness associated with the drawing of new images that detracts from the illusion of realistic movement. Conventional hand-drawn cartoon animation often uses 15 frames per second in order to save on the number of drawings needed, but this is usually accepted because of the stylized nature of cartoons. To produce more realistic imagery, computer animation demands higher frame rates.

Films seen in theaters in the United States run at 24 frames per second, which is sufficient to create the illusion of continuous movement. For high resolution, adapters are used.

Computer-generated animation is an umbrella term for three-dimensional (3D) animation, and 2D computer animation. These also include subcategories like asset driven, hybrid, and digital drawn animation. Creators animate using code or software instead of pencil-to-paper drawings. There are many techniques and disciplines in computer generated animation, some of which are digital representations of traditional animation - such as key frame animation - and some of which are only possible with a computer - such fluid simulation.

'CG' Animators can break physical laws by using mathematical algorithms to cheat mass, force and gravity, and more. Fundamentally, computer-generated animation is a powerful tool which can improve the quality of animation by using the power of computing to unleash the animator's imagination. This is because Computer Generated Animation allows for things like onion skinning which allows 2D animators to see the flow of their work all at once, and interpolation which allows 3D animators to automate the process of inbetweening.

For 3D computer animations, objects (models) are built on the computer monitor (modeled) and 3D figures are rigged with a virtual skeleton. Then the limbs, eyes, mouth, clothes, etc. of the figure are moved by the animator on key frames. Normally, the differences between key frames are drawn in a process known as tweening. However, in 3D computer animation, this is done automatically, and is called interpolation. Finally, the animation is rendered and composited.

Before becoming a final product, 3D computer animations only exist as a series of moving shapes and systems within 3d software, and must be rendered. This can happen as a separate process for animations developed for movies and short films, or it can be done in real-time when animated for videogames. After an animation is rendered, it can be composited into a final product.
For 3D models, attributes can describe any characteristic of the object that can be animated. This includes transformation (movement from one point to another), scaling, rotation, and more complex attributes like blend shape progression (morphing from one shape to another). Each attribute gets a channel on which keyframes can be set. These keyframes can be used in more complex ways such as animating in layers (combining multiple sets of key frame data), or keying control objects to deform or control other objects. For instance, a character's arms can have a skeleton applied, and the joints can have transformation and rotation keyframes set. The movement of the arm joints will then cause the arm shape to deform.
3D animation software interpolates between keyframes by generating a spline between keys plotted on a graph which represents the animation. Additionally, these splines can follow Bézier curves to control how the spline curves relative to the keyframes. Using interpolation allows 3D animators to dynamically change animations without having to redo all the in-between animation. This also allows the creation of complex movements such as ellipses with only a few keyframes. Lastly, interpolation allows the animator to change the framerate, timing, and even scale of the movements at any point in the animation process.
Another way to automate 3D animation is to use procedural tools such as 4D noise. Noise is any algorithm that plots pseudo-random values within a dimensional space. 4D noise can be used to do things like move a swarm of bees around; the first three dimensions correspond to the position of the bees in space, and the fourth is used to change the bee's position over time. Noise can also be used as a cheap replacement for simulation. For example, smoke and clouds can be animated using noise.

Node …

Read more on Wikipedia