INTERPOLATION AND LINEAR MOVEMENT
A roto artist needs to understand how a computer interpolates the frames between the user-defined keys. Understanding this concept will increase the speed at which you roto and will decrease the number of key frames and shapes you need to create accurate mattes.
The computer sees only in straight, even lines. When two key frames are created, the position frames between them will be created by the computer based on the relative X and Y values of the two keys. The movement projected by the computer will be linear, that is, a straight line between those two points, evenly distributed over the frames in between.
The computer doesn’t use the spline as a whole to calculate the position frames. Although you as a roto ...