it would be easier to help you, if you actually showed us what you are dealing with: screenshots and if you can - the actual shots. I am telling you this because the way you illustrated your situation is a bit abstract as if it's motion graphics and not Vfx Compositing - you do know that if it's not captured on camera - you don't need to use tracking to copy movements from one element to the other, right?
wish to now apply the position information of the Null Object to the green square so that it moves in the EXACT same speed and direction as the red square.
if you parent your green square to the null it will move like the null. if the green square has other keyframes, they will affect the movement
Essentially I'd like to stabilise the green square to remain in one place, and apply the position data from the red square to move the entire green square shot.
then you can stabilize the green square (again, as long as we are talking about Video and the green square was captured on camera as it moved) - you use the tracking information of the the green square to stabilize it. once stabilized you parent it to the null.
O.K these are two graphic elements moving on the screen. don't you have the keyframe information? is this a video for some reason and you need to track it? I am still trying to establish if this is a workflow problem because for me it seems you are trying to use tracking feature that is intended to pull keyframe information from a video, for a motion graphics projects that should be using native transform keyframe animation and not copy pasting tracking data. if this is all Chinese to you - you should really do some basics before trying to deal with this type of thing.
make sure at least some of this is well known to you before going any further:
if you have the project file with the red square and the green square and you want the green square to move same as the red you can either remove all keyframes from the green and attach it by parenting to the red, or copy the keyframes from the red to the green to make it exactly the same.
of course if there is a reason you have to work with video files that do not contain the key-frame data, you would have to do this manually or by tracking to retrieve to keyframe information but I am not sure this is the case.
you are either making your first steps in the software, or you are using it after some experience that makes you use this specific rather unusual workflow. it's important to know why exactly why are you using this strange workflow so we can help you and also to spare you for obvious explenations about the software.
The reason I'm using the red/green square video files (and hence maybe causing a little confusion) is because I want to stitch together two shots and blend them to make it look like one continuous take.
Take the idea of this being a vfx shot complete out of the equation as I will replace the squares with tracking marks taken from actual video footage of two shots (which obviously won't have keyframes). I wanted to learn the core of motion tracking by using unambiguous tracking marks rather than real world files which throw in a lot more variables than I am capable of understanding right now. Just want to make sure I have a good grasp of the basics.
Hope this cleared things up.
OK now it's much more clear. thank you
My suggestion is that if you want to add/blend two movements together from two trackers for 2 shots to maintain flow of motion is that you can try to do this in 2 main techniques:
try to do this by looking at the speed/value of your keyframe data via graph editor and manually averaging the both together as a new movement: copy two nulls information into a 3rd null and deleting keyframes and using keyframe interpolation to make a smooth flow of motion. there are limits to the flexibility of how smooth it will actually look - a pan left won't be so easily merged with a tilt down. I assume that some preparation is also required before you shoot (staying approximately in the same speed and angle for instance)
2. Script / Experssion
Another option is using a script or expression to add/blend two motions together: if you have 2 nulls and you want to connect them together, or maybe you want to average or blend 2 nulls position you can use a script called TrackerViz: TrackerViz - aescripts + aeplugins - aescripts.com this will blend them together, if you want to create a null that simply connects two motions together you can use an expression. I actually struggled with something like this (but for different reasons) not to long ago see here: mix (add) 2 layers position information into one - script/expression?. eventually this was not good enough because I had to connect MANY point trackers together to one movement so this saved me: http://aescripts.com/good-parents/
I would recommend taking a tracking course if you want to be prepared to many contingencies you may encounter in a vfx track. these 2 are very good:
These will give you a comprehensive understanding of what you can and possibly can't do with motion tracking.
I believe the example you provided is a bit extreme. maybe with a more straightforward example it will be easier to explain and see what are your options.
Thanks a lot
I'll definitely watch some more tutorials and see if the scripts you've mentioned work!
You're welcome buddy. no need to get ahead of yourself. start with the basics and make sure they are from good authors so you won't get confused with inaccurate information.