[IGSTK-Users] reg Polaris Spectra tracker

[somi]

Hi Patrick,
Thanks for the reply. I had few more queries.

I have attached a log file showing, the start time , expiration time and
their difference ( exp time - start time) for 5 frames ( 4 tracker tools
connected to tracker).
Only tool 1 and 3 were visible, while 2 and 4 were hidden.

a) As you had mentioned, I notice about "0.03 ms" difference in start times
of the tool in a particular frame.

b) I also notice the expiration time doesn't change for tools which were not
visible

c) Also the difference between start time and expiration time is not
constant.

Shouldn't the difference ( exp time - start time) be constant and be equal
to the tracking frequency of the tracker ?
Is there a way to determine how fast are we actually tracking ?


Thanks,
Somi

On Tue, Nov 9, 2010 at 11:16 AM, Patrick Cheng <cheng at isis.georgetown.edu>wrote:

> Hi Somi,
>
> That's a good question.
>
> In IGSTK we use timestamp to keep things in sync. Each transform will be
> timestamped at its origination with certain valid time period, depending on
> tracker update frequency and an overlapping constant.
>
> You can check validity of each transform's timestamp after you have
> obtained transforms from all your tracker tools. The timestamps' start and
> end time will be slightly different, as transforms are updated sequentially.
> But they should have similar lifespan as they are refreshed within one
> tracker update cycle.
>
> It might not be as accurate as the frame number in Polaris. But given
> Polaris's tracking frequency, this should be a valid solution.
>
> Patrick
>
>
> On 11/9/10 9:58 AM, somi wrote:
>
>> Hi,
>>
>> I have a Polaris tracker with 4 tracking tools attached to it.
>> During the tracking update look I use "
>> tracker_tool->RequestGetTransformToParent() "
>> to get the transform.  See the pseudo-code below for details.
>>
>> How do I make sure that the transform received for all the Tracker tool
>> objects is from the same
>> frame. Polaris frames have a unique frame number for each tracking data,
>> which I could probably use. Is there any way to access it ?
>>
>>
>> UpdateLoop()
>> {
>>
>>      // Update Tool 1
>>        tracker_tool1->RequestGetTransformToParent();
>>         if (coordObserver1->GotTransform())
>>        {
>>             TransformType transform;
>>             transform = coordObserver1->GetTransform();
>>             if ((is_visible = transform.IsValidNow()))
>>                    {
>>                    copy transform data
>>                     }
>>          }
>>
>>
>>
>>
>>           // Update Tool 2
>>        tracker_tool2->RequestGetTransformToParent();
>>         if (coordObserver2->GotTransform())
>>        {
>>             TransformType transform;
>>             transform = coordObserver2->GetTransform();
>>             if ((is_visible = transform.IsValidNow()))
>>                    {
>>                    copy transform data
>>                     }
>>          }
>>
>>
>>
>>  .... update other tools
>>  }
>>
>>
>> here, coordObserver is an igstk::TransformObserver
>>
>>
>>
>> Thanks,
>> Somi
>>
>>
>>
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Start Time1:	1289321631474.3068847656 Expiration Time:	1289321631517.6115722656	Diff:	43.3046875000

Start Time2:	1289321631474.3349609375 Expiration Time:	1289321585290.6450195312	Diff:	-46183.6899414062

Start Time3:	1289321631474.3520507812 Expiration Time:	1289321631517.5861816406	Diff:	43.2341308594

Start Time4:	1289321631474.3701171875 Expiration Time:	1289321586494.1398925781	Diff:	-44980.2302246094
++++++++++++++++++++++++++
--------------------------

Start Time1:	1289321631480.2329101562 Expiration Time:	1289321631517.6115722656	Diff:	37.3786621094

Start Time2:	1289321631480.2639160156 Expiration Time:	1289321585290.6450195312	Diff:	-46189.6188964844

Start Time3:	1289321631480.2880859375 Expiration Time:	1289321631517.5861816406	Diff:	37.2980957031

Start Time4:	1289321631480.3129882812 Expiration Time:	1289321586494.1398925781	Diff:	-44986.1730957031
++++++++++++++++++++++++++
--------------------------

Start Time1:	1289321631496.9589843750 Expiration Time:	1289321631517.6115722656	Diff:	20.6525878906

Start Time2:	1289321631496.9929199219 Expiration Time:	1289321585290.6450195312	Diff:	-46206.3479003906

Start Time3:	1289321631497.0109863281 Expiration Time:	1289321631517.5861816406	Diff:	20.5751953125

Start Time4:	1289321631497.0290527344 Expiration Time:	1289321586494.1398925781	Diff:	-45002.8891601562
++++++++++++++++++++++++++
--------------------------

Start Time1:	1289321631542.7680664062 Expiration Time:	1289321631586.0732421875	Diff:	43.3051757812

Start Time2:	1289321631542.7990722656 Expiration Time:	1289321585290.6450195312	Diff:	-46252.1540527344

Start Time3:	1289321631542.8229980469 Expiration Time:	1289321631586.0461425781	Diff:	43.2231445312

Start Time4:	1289321631542.8479003906 Expiration Time:	1289321586494.1398925781	Diff:	-45048.7080078125
++++++++++++++++++++++++++
--------------------------

Start Time1:	1289321631545.2180175781 Expiration Time:	1289321631586.0732421875	Diff:	40.8552246094

Start Time2:	1289321631545.2480468750 Expiration Time:	1289321585290.6450195312	Diff:	-46254.6030273438

Start Time3:	1289321631545.2709960938 Expiration Time:	1289321631586.0461425781	Diff:	40.7751464844

Start Time4:	1289321631545.2949218750 Expiration Time:	1289321586494.1398925781	Diff:	-45051.1550292969
++++++++++++++++++++++++++