chapter  12
Tweening in code
Pages 20

Traditional cell animation was, until relatively recently, shot on a camera that was mounted to point vertically down. This set-up was called a rostrum camera or an animation stand. The only movement the camera could do was to move up and down a very rigid column. The artwork was placed on a bench underneath the camera. This bench could move north, south, east and west in relation to the camera. On most animation stands, the bench could also rotate through 360 degrees. By moving the bench the artwork could move in a controlled fashion beneath the camera; by moving the camera up and down the column the camera could be made to zoom in or out of the artwork. In the early days of rostrum cameras the movement of each axis was linked to a manual counter. The counter would often count up in thousandths of an inch. To creating a smooth motion from one position to another on such a camera would require the use of a look-up table for each axis. The cameraman would first calculate the movement for each axis, then find the nearest look-up table to achieve this movement in the desired number of frames. The look-up tables incorporated an acceleration from

cameraman had a move that went through several positions they would have to use some kind of smoothing to make the movement through a middle position seem smooth. Most of the tables that were used to give these camera moves used a sine curve as a ramp in and out. A rostrum cameraman’s life was transformed when computers became available to control the motion of each axis. Many years ago I was involved in creating the software to drive the motors for an animation stand. The maths used to control the stands is the same that you will find in this chapter and the curved motion is still used to provide the movement of many motion control stands that are the big brother of an animation stand.