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Setting Up Constraints
The Stereo Geometry panel can be used to set up constraints between the two cameras. If you will be using the inter-ocular distance to set the overall scale of the scene, then you should do that initially, before setting up a coordinate system using the
*3 tool. The *3 tool will recognize the inter-ocular distance constraint, and generate a modified set of tracker constraints to avoid creating a conflict with the inter-ocular distance constraint.
The left-most column on the Stereo Geometry panel sets the solving mode for each of the six stereo parameters; they can be configured individually and often will be. The default As-Is setting causes no constraint to be generated for that parameter. To
constrain the Distance, change its mode to Known, and set the Lock-To Value to the desired value.
The Lock-To value can be animated, under control of the Make Key button at top left of the panel. With Make Key off, the lock value shown and animated is that at the beginning of the shot. Beware, this can hide any additional keys you have already created.
Usually it will be best to solve a shot once first, with at most a Distance constraint, and examine the resulting camera parameters. The stereo parameters can be viewed in the graph editor under the node “Stereo Pairs.” The colors of the parameters are shown on the stereo panel for convenience.
Sudden jumps in a parameter will usually indicate a tracking problem, which should be addressed directly. The error is like an air bubble under plastic—you can move it around, but not eliminate it. The stereo locks are all ‘soft’ and can not necessarily overcome an arbitrarily large error. If you do not fix the underlying errors in the tracking data, even if you force the stereo parameters to the values you wish, the error will appear in other channels or in the tracker locations.
Usually, the other four stereo parameters (other than distance and vergence) are constant at an unknown value. Use the Fixed mode to tell SynthEyes to determine the best unknown value (like the Fixed Unknown lens-solving mode).
If you are very confident of your calibration, or wish to have the best solve for a specific set of parameters, you can use the Known mode for them also.
In the Varying solving mode, you can create constraints for specific desired ranges of frames, by animating the respective Lock button on or off. The parameter will be locked to the Lock-To value for those specific frames. The Hold button may also be activated (for vergence and distance); see the following section on Handling Shots with Changing IOD or Vergence.
Note that usually you should keep solving “from scratch” after changing the stereo constraint parameters, rather than switching to Refine mode. Usually after a change the desired solution will be too far away from the current one to be determined without re-running the solve.
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