An animation is defined as a visual change in a scene with respect to time. The visual change in the scene is not only associated with the change in the position of the object, but also with its shape, color, transparency, structure and texture. An important point about animation is that it usually signifies the hand drawn or artificially drawn sequence of images, which contrasts to the movies where actors' performances with real-world online anime free scenes are recorded. In early times, animations were made by hand by drawing every scene one by one on paper and then painted.This method was obviously very troublesome and time-consuming. Nowadays, the use of computer technology has made the animation process progressively simpler and more powerful. The process of drawing images and playing them back at a high speed with the help of computer software in order to create an illusion of movement is referred to as computer animation. The illusion of movement is created by displaying an image on the computer screen, then quickly replacing it by a new image, which is similar to the previous image, but shifted slightly.

The field of computer animation is a subset of both computer graphics and animation technologies. Computer animation is generally achieved through a series of geometric transformations-scaling, translation, rotation or any mathematical technique-to produce a sequence of scenes. In addition, the animation can be produced by varying any of the following:

· Camera parameters: It involves the camera position with respect to the object, distance from the object, orientation, and focus.

· Lighting conditions: It involves direction and color of light, number of lights, and so on.

These days computer animation is widely used in the entertainment industry for producing motion pictures, cartoon movies, and video games. In addition, it is being used in education and training, industrial applications, virtual reality systems, advertising, scientific visualization and many engineering applications.

In the early days, an animation sequence was created by drawing different images in different frames and then showing them at a high speed. However, these days, animations are created with the help of computers. In computer animation, the frames required for animation are generated using computers, and are then displayed on an output device at a high speed. A basic approach to design an animation sequence consists of the four stages, namely, storyboard layout, object definitions, key frame specifications, and generation of in-between frames.

i. Storyboard layout: The storyboard is an outline of the action. This stage basically defines the motion sequence of the object as a set of basic events that are to take place. For example, while creating an animation sequence of cricket play, the storyboard layout would consist of action and motion of batting, bowling, fielding, running, and so on. Depending on the type of animation to be created, the storyboard consists of a set of rough sketches, models, or even in some cases it could be verbal description or list of basic ideas of the motion.

ii. Object definitions: Once the storyboard layout has been prepared, the next step is to define all the objects or participants in the action. The objects are generally described in terms of their dimensions, shapes (such as polygons or spline surfaces), colors, movements, or any other additional information which can help in defining the objects. For example, while creating animation for cricket play, the object definitions could be player's dimensions, colors of their uniform, dimensions of the ball, bat, stumps, etc.

iii. Key frame specifications: The next step in the process of creating animation is to specify key frame specification. A key frame is a detailed drawing of the scene at a certain time in the animation sequence. In each key frame, the position, color, shapes, etc., of all the objects is positioned according to a particular point of time for that frame. More the number of frames, smoother will be the animation. For complex motions, one need to specify more key frames as compared to simple, slowly varying motions. Some key frames are specified at extreme positions, where others are spaced such that the time interval between them is not too large.

iv. Generation of in-between frames: Once the key frames are specified, the next step is to generate intermediate frames. The total number of in-between frames required for an animation depends on the display media that is to be used. For example, film requires 24 frames per second, and graphics terminals require more than 60 frames per second. Typically, time intervals for the motion are set up such that there are three to five intermediate frames between any two key frames. In addition, some key frames can also be duplicated depending on the speed specified for the motion. For example, for a one-minute film sequence with no duplication, 1440 frames would be required, and if we put five intermediate frames between any two key frames, then 288 key frames would only be required.

There are twelve basic principles of animation which were introduced by the Disney animators Ollie Johnston and Frank Thomas in 1981 in their book The Illusion of Life: Disney Animation. The main aim of the principles was to produce an illusion of characters adhering to the basic laws of physics. However, these laws also dealt with more abstract issues, such as emotional timing and character appeal. The twelve basic principles of animation are described as follows:

· Squash and stretch:It is the most important principle of animation. Its main purpose is to give a sense of weight and flexibility to the drawn objects. Stretch and squash technique is basically used for simulating accelerating effects especially for non-rigid objects. This technique can be applied to simple objects like a bouncing rubber ball, as well as to complex constructions like musculature of a human face. For example, when a rubber ball bounces and hits the ground, it tends to get flatten on hitting the ground. This is squash principle. As soon as the ball starts bouncing up, it stretches in the direction of its movement. This is stretch principle. Another example is the stretching and squashing of a human face. When the muscles of human face are stretched or squashed to an exaggerated degree, it can give a comical effect. The most important aspect of this principle is the fact that the stretching and squashing of an object does not affect its volume. That is, no matter how an object is deformed, it should still appear to retain its volume.

· Timing: Timing is the most vital element of an animation. It refers to the spacing between motion frames.The more is the spacing between the frames, the faster the object will appear to move. The speed at which an object is moving gives a sense of what the object is, what can be the weight of an object and why it is moving. Timing in an animation is significant for establishing the mood, emotion, and reaction of a character. For example, the blinking of an eye can be fast or slow. If it is slow, a character seems to be tired and lethargic. However, if it is fast, a character seems to be alert and awake. Timing can also be used to communicate important aspects of the personality of a character.