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Rosalind Coombs
05-01-2003, 10:43 PM
Dear List Members,

Original posting:
We are looking for a Body Builder Plug-In for the Vicon system using the Bell
model for calculation of the hip joint centre.
Does anyone know of where we could access this or be able to forward any
relevant info to us as we need the information as soon as possible to convert
our old motion analysis files.
Thank you in advance for your help. As usual a summary of replies will be
posted for all to read.

I received a few replies regarding my posting above generally suggesting the
same thing. These are summarised below. Thank you to those who responded.
Your help was much appreciated and we will be able to move on with our
research because of this. Thanks again.

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Rosalind,

I don't know of any existing plugins for the Bell model but Tim Pitt
("Timothy Pitt" ) runs a consultancy developing PlugIns
and the like. He was one of the bio-engineers/programmers who wrote the
original BodyBuilder code but now works independently. He's done some work
for me with excellent results.

Obviously he makes his bread and butter by offering these services but is
not expensive and if you want a good job doing well I'd thoroughly
recommend contacting him. He'd also tailor something to do exactly what you
wanted which I think would be very useful for you.

Richard
Richard Baker PhD CEng
Gait Analysis Service Manager and Director of Research
Hugh Williamson Gait Laboratory, Royal Children's Hospital, Victoria 3052,
Australia
Tel: +61(0)3 9345 5354, Fax: +61(0)3 9345 5447

Adjunct Associate Professor, La Trobe University
Honorary Senior Fellow, University of Melbourne
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Hello Roz,

If you are unsuccesful finding a BodyLanguage Bell model (I'm assuming you
have BodyBuilder with PlugIn Modeller) or would like any other PlugIns to be
sorted out for your file conversion then I'm sure I could sort something out
for you. This is exactly my speciality. To see what kinds of things I've
done already, have a look at my website (www.vaquita.co.uk) and for a
reference talk to somebody at Vicon. Maybe my ASCIIImport PlugIn would help?

Tim

Vaquita Software www.vaquita.co.uk
Lets you concentrate.
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Hi Roz,

This is the code I use in BodyBuilder to calculate hip joint centre from
Bells method.

First define the pelvis anatomical system. I use 4 points on the pelvis (left
and right ASIS and left and right PSIS)

midASIS=(LASIS+RASIS)/2
midPSIS=(LPSIS+RPSIS)/2
Pelvis=[midASIS,RASIS-LASIS,midPSIS-midASIS,zyx]

Then set up the offset factors as per Bell

$%LeftHipOffsetFactor={-0.19,-0.3,0.14}
$%RightHipOffsetFactor={-0.19,-0.3,-0.14}

Then calculate the hip centre location in the pelvis anatomical system:

IntASISdist=DIST(LASIS,RASIS)
%RASIS=RASIS/Pelvis
%LASIS=LASIS/Pelvis
%RHJC=%RASIS+(IntASISdist*$%RightHipOffsetFactor)
%LHJC=%LASIS+(IntASISdist*$%LeftHipOffsetFactor)

And finally convert it back to the global systrm:

RHJC=%RHJC*Pelvis
LHJC=%LHJC*Pelvis

Hope this helps. Please feel free to e-mail if you want more advice.

Vicky Hood

Research Assistant
Bioengineering Unit,
Strathclyde University,
104 Rottenrow,
Glasgow,
G4 0NW

+44 (141) 548 3228
e-mail victoria.hood@strath.ac.uk
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Roz Coombs

School of Health & Bioscience
University of East London
Romford Road
Stratford
London E15 4LZ
UK

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