# Interpolate two sets of tracking points

Lets say I have two sets of tracking points with the same number of points/set, is it possible to associate points from one set to the other and make them interpolate in time?

EDIT:

As suggested by @poor, I'll try to clarify what I try to achieve. This question originates from @cegaton's comment in 2D morphing video images.

I am trying to use the tracker to morph from two video sequences. Imagine two videos, first video has a square moving from left to right of the screen, second video has a rectangle moving the same way. I track four vertices of square as object A and the rectangle's as object B. Both tracking points move according the the image of its video from left to right, but what I want is to interpolate those tracking points (I don't know if creating a new object C or just modifying one of the existing objects) so that at the same time they move from right to left they also aproximate positions of object's A points to object's B points. In the end we will have four points moving both from left to right and adjusting position from A to B thus making posible using on a plane two videos that distort and fade from video A to B.

Hope this makes sense.

• Please add more information and the context if possible - hard to tell without seeing the plate. Two sets in one shot? Are you sure that the marker positions of both sets are equal?
– p2or
Sep 30, 2015 at 8:21
• Not sure if this helps, but youtube.com/watch?v=oBBv4Plk0cw shows (among other things) how to constrain a still picture backdrop to move and resize according to a video foreground. This looks like a technique that can be adapted to similarly move and resize your videos so that the square and rectangle move together. You can then use keyframing to make the square eventually become a rectangle.
– user31002
Oct 21, 2016 at 13:07
• Thanks @C.W. but that is not what I was looking for, that is tracking a background and replacing it with an image that tracks and stretches accordingly. What I wanted to achieve (which I finally did with another program, you can check it out in minute 3:30 of the next video: youtube.com/watch?v=f8PcW7V9PSY) is a morph but from two moving videos instead of two still images. Oct 22, 2016 at 20:06

Let's say you want to interpolate the movement of empties between frame 0 and 50

1. create one empty for each tracking point of set A.
2. add a constraint to the empty associating with tracking point 1 of set A
3. add a constraint to the empty associating with tracking point 1 of set B
4. set the influence of the first constraint to 1 and add a keyframe
5. go to frame 50, set the influence to 0 and add a keyframe
6. do the inverse of steps 4 & 5 for the second constraint (0 --> 1)
7. Repeat steps 2-6 for the other tracking points

This strictly answers your question of how to interpolate between tracking points (you might need to adjust the curves to be linear).

However since you need to morph the next logical step was to use the empties as hooks to deform a mesh. However the hooks need to modify the position of the vertices directly and not relatively as they do (see this queston ). Still, the half-solution here is worth sharing.

I tend to double press G to move pattern to offset relative to marker position, finding any discernable feature that is on similar axis in real world and visible while the actual marker is obstructed. Track the offset pattern and join two tracks afterwards. Minor sliding can be fixed by overlapping two trackers and joining them with ctrl+J or manual adjustments.