Set the motion scale factor to X (default value 0.5). These
commands scale their motion by an amount which depends on the
distance from the frame to the center and on the size of the
frame. Specifically, they scale by
dist + scaleof(frame) * motionscale
where dist is the distance from the center to the frame and
motionscale is the motion scale factor set by this function.
Scaleof(frame) measures the size of the frame object.