Exporting 2D Trackers to 3D Applications
This tutorial shows the use of two scripts that convert 2-D tracking data into 3-D motion-capture-style paths that can be exported to 3D applications (which generally don't know anything about 2D trackers).
One script creates a path that is a fixed distance from the camera, either on the surface of a sphere (as-the-crow-flies distance to the camera), or on a plane (constant distance along the camera pointing axis)
The second script creates a path that is along the surface of a selected mesh. The mesh might be a ground plane, or a sphere, or a complex object such as a mesh model of an actor's head. This latter possibility offers a way to get motion-capture information on facial expressions, from a single-camera shoot --- by tracking the head to the shot as a rigid-body, then tracking facial features and reprojecting them onto the moving head mesh.
I don't actually export anything to any other app in this tutorial. Once the 3D paths have been created, there's nothing different to it, it exports like any other scene to your target application.
(PS - in the tutorial I said corners of the mouth and eyes, but had in mind corners of the mouth and pupils)