In traditional paper animation, animators often use the following method :
* First the key images are drawn. The purpose is to get a handle on the global movement, on the required number of images, on the timing to schedule, etc ...
In the example opposite, the kid is running from the left to the right of the screen. Two key images are drawn.
* The second step is to locate and draw the most important frames. In our example, this is when the kid is jumping (the two feet are not on the floor).
* Finally, the inbetween pictures are added : to begin, an image is drawn between each picture already visible on the timeline.
After this, new inbetweens are added among the previous one. this usually helps a lot to obtain a good quality of animation (in other words a smooth flow of movement)
* The subdivisions are repeated until the animator is satisfied of the rendering.
This simple process needs some successive subdivisions along the animation layer of the timeline. That's not always easy because the images duplication, creation or copy are not always convenient to use. Adjusting the timing of the whole animation usually needs to duplicate and/or delete some frames and can be time consuming.
That is the reason why the use of the images instances is clearly advised.
In this chapter :
* The blue images are the new ones.
* The gray images are those which have been drawn in one of the previous steps.
* The green images are here to show the global render of the animation, once it is finished.