[Rock-dev] using the vicon component

[Javier Hidalgo Carrió]

On 01/08/2014 04:57 PM, Martin.Azkarate at esa.int wrote:
> Hi there,
>
> Happy new year to everybody.
>
>
> We did some investigation and the error is not in the component not 
> finding the subject. The error comes from the fact that the Nexus 
> software does not calculate the coordinate system for the 
> subject/segment in Live mode.
>
> If you look at the subject_segment_definition image attached you will 
> see there a coordinate system clearly defined for it. We are using a 
> wand with 5 markers, 3 of them are labeled and used to define the 
> segment coordinate system and 2 markers are left unlabelled.
>
> In the live_stream_data_SDKTest image you will see a snapshot of the 
> Nexus software running live (no capture process started) and another 
> window showing the output of a console application that is provided as 
> a testing program with the Vicon SDK v1.2. Note in this window that 
> the Global Translation and the Global Rotation Quaternion vectors for 
> the segment are all zero (which is an invalid quaternion value). 
> Basically Nexus does not calculate (in live mode) Global values for 
> the segment but just positions of markers. See position vectors for 
> (3) labeled and (2) unlabeled markers are properly calculated.
>
> If you look at the output image of the test_vicon ruby scripts 
> (attached script with slight modification to include another reader 
> for the unlabeled markers port) you will see that it shows NaN for the 
> translation values of whole subject rigidbodystate type (wrong 
> quaternion screws the transformation matrix values) but it shows the 
> same values we could see in the live_stream_data image for the 
> unlabelled Marker #0 (or Maker #1) position values.
>
> So, we've been told by some colleagues at ESTEC that in fact *we need 
> to use the Vicon Tracker software to have this in live mode (the Nexus 
> is not enough)*, however I believe that when this component was 
> developed in first instance it was done using the Vicon Nexus, or 
> that's what I was told. So maybe we are missing something or we need 
> to prepare the Nexus software to calculate/provide this data in live 
> mode too. *Anyone using the Vicon component nowadays can tell us how 
> does configure/prepare the Vicon Nexus and define the subject/segments?*

Hi Martin,

I remember there is a way in the Nexus software to set the real time 
kinematics calculation. It seems you are missing this step.
I don't know why but I think it is not set up by default. In order to do 
that:

1. Go to the "System" tab inside the "Resources" windows (left part of 
the e.g.: live_stream_data_SDKTest image)
2. Click in the "Local Vicon System [100Hz]"
3. Below in "Properties" sub window, in "Core Processor" field
4. In "Processing level:" set it to "kinematic fit" in the deployed list.

I hope this is the way to set it up. Otherwise, it should be in the 
Nexus documentation. It might change among different Nexus versions.

Javier.


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