Ive been thinking about this for a while now and haven't really come up with the perfect solution.
I have a model of an iphone which i have rendered out of Cinema 4D with a couple of fairly simple camera moves.
I want to composit it into AE and have a few 'labels' which track the phone with various information attached.
Im sure you've seen something similar before.
But Im having trouble with two issues:
1, The 'line' tracking the phone. Can i create a line (new solid > stroke) and track an object with both ends of my stroke? So it basically looks like the line is attached to both the rendered phone and my 'label'. which is just a basic text box.
2, Can i do this in 3D space? without, say 3D stroke?
Do I have the right idea? I don't think it would be better to do all the labels and info inside Cinema, this would be tough to light, modify, etc...
I've been thinking about the tracking part of it for a while. Even without the Cinema4D part, Ive always wanted to track two objects with one line. Almost how the motion tracker points look when you track rotation and position.
Yes, you can track the ends of the line in 3D space. Search graymachine.com for the toComp expression tutorial. I think he uses a beam effect in that example and that might work for your project as well.
A lot of the techniques for doing this don't take into account 3D perspective. If you want the line to appear in 3D perspective then you need to add expressions to the start and end size of the Beam effect. This is covered here:
That post only covers the "Ending Thickness" of the beam. For the "Starting Thickness" you'll have to point the expression to the Null that corresponds to the start point and switch the layer variables.