I have some footage of a cylindrical canister with a label on it that needs to be tracked and then the label replacing. The tracking is good, I don't have any issues with mocha doing that, but there is a slight twist as someone picks up the canister and removes it from the shot. I was thinking I could use the 3D curvature under geometry options to turn the label slightly as it tracks but that's not working.
Here's a screen shot: (imagine as she picks it up she twists it like 5 degrees)
Sorry for the late reply I was away on leave and only just found this!
With curved tracks you'll have two issues:
Point 1 is fairly straightforward: you need to warp the tracked element using a warping tool, such as bezier warp or similar. It's kind of faking it, but when you're dealing with a planar track for an insert that is cylindrical you need to distort that element accordingly. There's not much of a way around it. In mocha Pro we handle this using the warp tools in the insert module for example.
For point 2, if the label is disappearing around the corner of the cylinder you'll also need to mask the object edges so the insert doesn't fall off the edge and appear to be floating like it's peeling off. A warp will help with this, but only so far as you'll end up squishing it more and more to fit to the edge, and that won't look natural.