Because everything in real life moves at different speeds and at different points in time, follow-through and overlapping action are essential for conveying genuine and fluid movement. The concept of follow through refers to the idea that distinct components of the body will continue to move after the character has come to a halt. For example, if a character extends her arm while running, the arm should still be extended when she stops because muscles contract slowly but are still working even after they have been stimulated by nerve signals to stop moving.
Overlapping action is when one action overlaps or is done simultaneously with another. This is used extensively in animation to create excitement and drama. A great example is seen in the Kung Fu movies where various attacks are done by different characters over one another creating a flurry of activity that we can only see as one continuous event.
Follow through and overlapping action are necessary in animation because without them your characters will appear stiff and robotic. If you want your characters to look natural then they need to be able to show some muscle when pulling their punches or kicking down doors.
The trajectory of a moving item is the route of activity. Make sure you don't mix up the route of action with the line of action. Individual drawings feature a line of motion that represents the visual flow of activity in that specific picture. In an animation, the route of action denotes the trajectory of a series of drawings. It's important to understand that while both the route of action and the line of action represent movement, they do so from different perspectives.
The route of action is used to describe the visual flow of an animated sequence. It includes such details as which way the characters are going, what objects or people are involved, and how long each scene will last. The route of action can be seen as the "storyboard" of the film.
The line of action is drawn from one drawing to another and usually indicates where on the body someone is looking. It's used by the animator to show where attention should be focused in order to make the scene come alive. Although the line of action is essential for making drawings move, it isn't always visible. If something hidden by another object is going to move, then the artist must indicate this by some other means- typically with a few simple lines.
In general, the route of action tells us how to get from one place to another while the line of action points out specific parts of the body that need to be moved in order to create a visually interesting image.
Stop-motion animation is more difficult because you have to take a lot of images of every precise movement, which takes a lot longer, but hand-drawn animation is easier since you can just create the movements page by page, which takes less time.
In this section, we will look at each of the animation principles in further detail.
An optical illusion is used to create animation. When a series of still photos is shown in rapid succession, the viewer sees them as a continuous moving image. This is the same mechanism that allows live-action filming and projection to function. The slot functions as a shutter, freezing the picture for a brief duration. When the camera or projector is triggered again, it begins recording at the beginning of the next frame.
Optical illusions can be created by using different objects in each photo, such as a car with its headlights on or off, a hand with a rock in it showing one side then the other. These objects must be changed quickly enough for the viewer's eye to have time to catch up. A more advanced technique uses computer graphics; these images are stored in data files and displayed on a screen or projector via a process called video mapping. Video mapping is useful for creating animations that change shape or position during the sequence, such as a ball rolling across a table into the path of a knife.
Animations can also be created with simple drawing tools on your computer. One program used for this purpose is Adobe Flash. With it, you can make movies featuring characters that walk around the screen, talk, play instruments, and so forth. You interact with these characters by clicking on icons or buttons displayed on the screen.
Characters can also be controlled by using special effects built into most web browsers.