Zero Acceleration (Constant Speed)

Now, the time spacing for the in-betweens that is: in-between frames is at equal interval; which is if, we want N in-betweens for key frames on time Ta and Tb, after that, the time interval among key frames is divided in N+1 sub-intervals leading to in-between spacing of ? T specified by the expression in the figure.

Hence, the time of any Jth in-between can be determined by

Tj = Ta + J* Δ T

Here J = 1, 2, 3, .......,N

Note: A linear curve directs to zero acceleration animation.