I currently have a project with floating text blocks in 3d space...
there are about 10 layers, each stacked at a different level in 3d space... they all have a wiggle expression applied to position, and float around... I've pre-composed all those layers... now, I want to use tracking to add little rolling numbers next to the text blocks, that will obviously follow the texts motion... when I try to track each layer separately, the motion source menu contains all the layer names, but theyre greyed out... thats why i pre-comped everything... the motion source now works with the pre-comp, but when i choose my point, and click analyze, the tracker doesnt move at all...
I wouldn't bother tracking anything.
You already have the exact position data of the floating text blocks in your precomp, you just need to pass it to the rolling numbers with the pickwip.
This can be a little tricky when pickwiping between two different comps but I find it useful to temporarily drag one comp tab up next to the effects tab (top left) then whilst seeing both comp stacks you can pickwip between them easily.
Additionally once pickwipped you can add additional expressions to the rolling number position to add secondary motion if desired.
3D animator and VFX specialist
If your rolling numbers are in the same comp as the text blocks then yes but I thought you had precomped the text blocks without the rolling numbers which means that the rolling numbers are outside the text block comp.
See the following image for a visual explanation of how to move the tabs: aeui.jpg