Computer Animation also called Digital Animation, is the technique of creating images in motion through the use of computers. More and more graphics are created in 3D, although 2D graphics are still widely used for slow connections and real-time applications that need to render fast. Sometimes the goal of animation is computation itself, others may be another medium, like a movie. The designs are made with the help of programs of design, modeling and finally rendering.
To create the illusion of motion, an image is displayed on the screen and is quickly replaced by a new image in a different frame. This technique is identical to the way in which the illusion of motion in films and on television is achieved.
For 3D animations, objects are modeled on the computer (modeling) and 3D figures are joined with a virtual skeleton (bones). To create a face in 3D model the body, eyes, mouth, etc. of the character and later are animated with animation drivers. Finally, the animation is rendered.
In most computer animation methods, an animator creates a simplified representation of a character's anatomy, as it has less difficulty in being animated. In biped or quadruped characters, many parts of the character's skeleton correspond to real bones. The animation with bones is also used to animate many other things, such as facial expressions, a car or other object that you want to provide movement.
In contrast, another type of realistic animation would be motion capture, which requires an actor to wear a special suit equipped with sensors, their movements being captured by a computer and later incorporated into the character.
For 3D animations, frames must be rendered after the model is completed. For 2D vector animations, the rendering process is key to the result. For recordings shot in advance, the frames are converted to a different format or to a medium such as a movie or digital video. The frames can be rendered in real time, as they are presented to the end user. Animations to transmit via Internet in limited bandwidths (ie. 2D Flash, X3D) use programs on the user's computer to render real-time animation as an alternative for the transmission and animations pre-loaded for high-speed links.
To deceive the eye and brain so that someone thinks they are seeing a moving object, the images should be displayed at about 12 frames per second or faster. At speeds greater than 70 frames / second, you will not notice an improvement in realism or smoothness in the movement of the image due to the way the eye and brain process the images. At speeds shorter than 12 frames / second most people will be able to detect a flicker at the moment the sequence of images is displayed and lessen the illusion of a realistic motion.
Conventional handmade animations typically use 15 frames / second to decrease the amount of drawing required, but this is usually accepted because of the nature of cartoons. Therefore, to create a realistic computer animation, a higher number of frames / second is required.
The reason that the blinking of the image at high speeds is not noticeable is because of the "persistence of vision". From moment to moment, the eye and brain working together store anything that is being watched for a fraction of a second, and automatically makes small, smooth "jumps." Movies that are shown in theaters run at 24 frames / second, which is enough to create this illusion of continuous motion.
In most 3D animation systems, an animator creates a simplified representation of the body of the character, analogous to a skeleton or stick figure. The position of each segment of the skeleton model is defined by "animation variables", or Avars.
In Human characters and animals, many parts of the skeleton model correspond to the actual location of the bones, but the animation model of skeleton animation is also used to animate other things like facial expressions (although there are other methods facial animation animation). "Woody", the character of Toy Story, for example, uses 700 Avars, including 100 Avars in the face. The computer does not render the skeleton model directly as usual rendering the skeleton is invisible, but uses the skeleton model to calculate the exact position and orientation of the character, which is eventually rendered in an image. By changing the values of the Avars on the timeline, the animator creates movement by performing the character frame by frame.
There are several methods for generating Avars values for realistic movement. Traditionally, the animators manipulate the Avars directly. Instead of creating Avars for each frame, they usually place the Avars at strategic points in the frames and allow the computer to transition between them, this process is called keyframing. Keyframing puts control in the hands of the animator, and is based on manual animation traditional animation.
In contrast, a new method called "motion capture" uses live action. When computer animation is performed by this technique, a real actor performs the scene as if it were the character to be animated. Its movement is recorded on a computer using video cameras and markers, and that movement is applied to the animated character.
Each method has its advantages, and until 2007, games and movies used some or both of them in their productions. Frame animation can produce movements that would be impossible for an actor, while "motion capture" can reproduce the characteristics of a particular actor. For example, in the 2006 movie Pirates of the Caribbean: Dead Man's Chest, actor Bill Nighy performed the character Davy Jones. Even though he practically did not appear in the film, the production benefited by recording the characteristics of his body language, postures, facial expressions, etc. This "motion capture" is appropriate in situations where realistic behavior is required, but the characteristics of a character exceeds what can be done with conventional make-up and costume.
There have been cases of excellent animations in various films, Final Fantasy The Spirits Within, Violet's Hair in The Incredibles, Scenario Animation in Toy Story, Tifa's Hair Movement in the Wind in Final Fantasy Advent Children, Animation of water in the Water Dance of the video game Final Fantasy X and the creation of monsters in Monstruos, SA (Monsters Inc.).