Combine 'Track Camera' and 'Track Motion' ?

[IanChap]

Not sure if this is possible:

I have a reverse-flown drone shot, and can use 'Track Camera', and then insert an image (a  'flag' and a name) and make the layer 3D. So far so good, my 'flag' dimishes in size as the drone flies away, staying static in it's 3D world.

But if the object I'm trying to attach to is moving. e.g. someone walking, can I also use 'Track Motion' at the same time?

Both of these I know how to do separately, but I want to combine them.

[Mylenium]

Sure you can, but honestly that's one of those "invisible elephant" questions we could discuss for days on end and not arrive anywhere. Show us what you have and explain what exactly you need and we can advise. In fact it could be that you don't need any 2D tracking at all, but rather simply need soem auxiliary construct in 3D like a Null moving from A to B to which your other stuff is simply parented or linked via an expression. Anyway, impossible to be precise without seeing your footage or at least soem screenshots.

Mylenium

[IanChap]

OK, here's a low-res of what I had, which was manually tracked in PP, hence a little jumpy.

I want similar but with the 'flags' being in 3D space, i.e. diminishing as they get farther away. The one 'Ian + Bikes' is simple as the target is stationery and using Track Camera before making the layer 3D does it. But 'Mr Doughty' is the problem as he's walking. I have the 'flags' as transparent PNG's (though maybe there's a better way?).

[IanChap]

Sorry here's the attachment....

[Mylenium · Accepted solution]

I'm not sure why you can't simply scale the callouts as they move away? Sounds like you are trying too hard to make a simple thing complicated. The perspective change would be very insignificant, anyway, at around 15% change in perceived scale. Otherwise what I already said might apply: Create two Nulls in 3D space that roughly are placed where Mr. Doughty is at the start and the end of the sequence, then interpolate with something like this on a third Null:

mStartPos=thisComp.layer("Start Null").transform.position;

mEndEnd=thisComp.layer("End Null").transform.position;

mStartTime=0;

mEndtime=2;

xPos=linear(time,mStartTime,mEndTime,mStartPos[0],mEndPos[0]);

yPos=linear(time,mStartTime,mEndTime,mStartPos[1],mEndPos[1]);

zPos=linear(time,mStartTime,mEndTime,mStartPos[2],mEndPos[2]);

[xPos,yPos,zPos]

Once you have that down, you can parent anything to the third Null and have it respond reasonably to camera perspective. Adjust the timing as needed, of course. Alternatively, instead of time you could also tie it to a keyframed slider. more complex stuff is certainly possible, but I think being too obsessive here would actualyl work against you, as no doubt you would prefer smooth motion over accurate, but jittery one...

Mylenium

[IanChap]

Thanks, "trying too hard to make a simple thing complicated" is probably correct, and I do realise there's more than one way of doing things.

I just wasn't sure if there was actually a simple way of doing the two tracking tasks together. Not particularly for this, but future reference. Now I know the answer!