On 01/08/2014 04:57 PM, [email protected] 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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