[Rock-dev] using the vicon component

[Martin.Azkarate at esa.int]

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?

We are using the Nexus v1.8.5, what version of Nexus are you guys using 
for this?


Kind regards,


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