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GeoH Track with 2D Trackers
The idea here is to use 2D SynthEyes trackers to track specific small point-like features on the object, and use them to control the GeoH rig so that each tracked feature on the rig appears at the correct location in the image.
This mode is much like a conventional SynthEyes object track, using a known mesh as a guide. Indeed the setup is the same. But here we'll create a solve for an entire hierarchical rig, not just a single animated object.
For the 2D hybrid setup, the trackers should be created or reparented onto the GeoH object that they are to control. (Once there are 2D trackers attached, the GeoH tracker uses them instead of doing image-based tracking.)
Each tracker needs to have 3D lock coordinates on the mesh, typically obtained using the perspective view's "Place" mode to literally place the tracker on the correct location on the mesh. In all cases, the tracker must be set to Lock Point on the Coordinates panel, so that it is locked to those coordinates, to be used for GeoH tracking. Place mode does that automatically.
Example : you are tracking shot of a car with a door that opens. The rig includes the entire car with a moving door region. You create a supervised tracker for the car door's handle, and place it on the car mesh at the handle.
Important : When using GeoH tracking with supervised tracking, be sure to turn off the GeoH Key button on the first frame, once you've gotten everything
set up. That will allow the first frame to be GeoH solved; GeoH Key button is for image-based GeoH tracking.
Crucial: When adding additional supervised trackers and GeoH objects for hybrid tracking to an existing rig, you need to place the tracker (to generate the 3D coordinates) only on parts of the mesh that are 100% deformed by its parent, and not at all deformed by siblings, at the time it is placed. Otherwise incorrect 3D locations will be obtained.
If you are setting up a tracker via a different method (than "Place"), for example a regular SynthEyes object solve or a zero-weighted-tracker (ZWT), you can use the Set Seed button on the Coordinates panel to transfer the already-solved coordinates to the lock fields for use with GeoH tracking. Remember to change the axis selection from Unconstrained to Lock Point.
The number of trackers required for a given GeoH object will depend on how many joints of the GeoH object are unlocked, and the overall geometry of the situation. You'll always need more trackers than half the number of unlocked joints. Additional trackers will typically provide more accuracy.
Tip : you can assign higher tracker weights to trackers that you have more confidence in, and vice versa, using the Trackers panel.
Be careful not to create situations where the unavoidable amount of noise in the images and tracking data produces large, unwanted, amounts of object motion. For example, three points on the cheek of a head may technically be enough to allow the cheek to move around arbitrarily. But since they are small and closely spaced, the resulting 3D data will likely have the cheek flying around quite unnaturally. Instead, try to use a smaller number of degrees of freedom, potentially changing over the duration of the shot.
©2023 Boris FX, Inc. — UNOFFICIAL — Converted from original PDF.