Hi,
I am currently using the Holzbaur upperlimb model and I am tying to connect an external object (rod) to the hand which is made via a cad software and saved into .vtp format . The external object/rod is around 100 mm in length and 30mm diameter. When I tried to add the object to the hand part I noticed the rod is pretty big and fills the whole screen while the skeletal body is comparatively small.
I have verified the dimension of my rod after converting to .vtp and its correct but didn't perform any scaling here, I have attached a pic of my rod scaled down to (0.001 0.001 0.001) to fit my hand size. I am a bit confused whether the object I introduced into opensim may have some problem with scale, or is that the generic model needs to be scaled up before it could be used as to make both skeleton and rod in same dimension.
Please advise the best way to proceed, sorry for trouble.
Thanking you
nitin
doubt with scaling
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Nithin Kurup
- Posts: 149
- Joined: Sat Jan 18, 2014 5:13 am
doubt with scaling
Last edited by Nithin Kurup on Mon Oct 06, 2014 4:53 pm, edited 1 time in total.
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Ayman Habib
- Posts: 2252
- Joined: Fri Apr 01, 2005 12:24 pm
Re: doubt with scaling
Hi Nitin,
The geometry of the bones is used only for visualization, and it assumes dimensions are given in meters by default (length units are given at the top of the model file). When exporting geometry from CAD you can decide what length units to use and convert accordingly.
Hope this helps,
-Ayman
The geometry of the bones is used only for visualization, and it assumes dimensions are given in meters by default (length units are given at the top of the model file). When exporting geometry from CAD you can decide what length units to use and convert accordingly.
Hope this helps,
-Ayman
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Nithin Kurup
- Posts: 149
- Joined: Sat Jan 18, 2014 5:13 am
Re: doubt with scaling
Hi Ayman,
Thanks again for your help.
So, does it mean that before I import my cad model into opensim, i need to convert it to opensim dimensions (m, normally) or viceversa and then when imported at scale factor of (111) my rod will be having relatively same size as that of bones and I don't need to down scale it.
My mistake was that my cad model dimensions were in mm whereas my model geometry in meters.
Thanking you again and have a nice day
Nithin
Thanks again for your help.
So, does it mean that before I import my cad model into opensim, i need to convert it to opensim dimensions (m, normally) or viceversa and then when imported at scale factor of (111) my rod will be having relatively same size as that of bones and I don't need to down scale it.
My mistake was that my cad model dimensions were in mm whereas my model geometry in meters.
Thanking you again and have a nice day
Nithin
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Ayman Habib
- Posts: 2252
- Joined: Fri Apr 01, 2005 12:24 pm
Re: doubt with scaling
Hi Nithin,
Indeed, that should do it.
Best regards,
-Ayman
Indeed, that should do it.
Best regards,
-Ayman
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Nithin Kurup
- Posts: 149
- Joined: Sat Jan 18, 2014 5:13 am
Re: doubt with scaling
Dear Ayman,
Sorry again for bothering you on an another topic. I had seeked help but I am stuck again.
Thanking you again,
Nithin
Sorry again for bothering you on an another topic. I had seeked help but I am stuck again.
Thanking you again,
Nithin
Last edited by Nithin Kurup on Fri Oct 24, 2014 6:13 am, edited 2 times in total.
Re: doubt with scaling
If you are looking at the motion by changing the crank coordinate in the GUI, then it is doing a an assembly at every change in the crank coordinate. An assembly tries to satisfy the current value of the coordinates and your constraints. If there are coordinates you don't care about (you want them to assume any value to satisfy the constraint) then you must tell OpenSim about it. You do that by setting the <is_free_to_satisfy_constraints> flag (in the Model XML file inside the Coordinate) to true for those coordinates that should be free to change (e.g. the pedal spindle coordinate and NOT the crank angle).