[IGSTK-Developers] calibration (followup to David and James's discussion)

[Ziv Yaniv]

David Gobbi wrote:
  ...

> The easiest way to do this, though I know James doesn't like it, is to 
> have a SetToolOrientation() method in the ToolTipCalibration.  The tip 
> calibration won't use this information to compute the tip position, 
> but it will include this orientation in the transform that it 
> produces.  That would be sufficient for providing an accurate tip 
> location and nominal orientation for the pointer.
>
> - David
>
This seems a reasonable approach, although it is ugly (giving a 
parameter to a method so that it only passes it on).
    Which brings me to the following scenario for getting the tool 
orientation based solely on pivot calibration.
     As we all know pivot calibration computes two translations 
simultaneously, the translation from the tool's tracking device origin
      to the tip and the transformation from the tracking systems origin 
to the location of the tool tip.
     To get an approximate orientation for our tool do the following:
      1. pivot calibrate at location one.
       2. pivot calibrate at location two.
       3. place the tool so that its axis connects location one and two, 
subtract the two points the resulting vector is the
           direction of the tool axis in the tracking system coordinate 
system.
     Assumption: During this process the relationship between the 
tracking system and points one and two remains fixed.

     a. This is crude and ugly.
     b. I'm not sure if the tool reference frame can be seem for all 
three steps when using optical trackers.
     c. It fits right in with the SetToolOrientation approach.

                                                                   Ziv