simtk.org

I'm trying to reading the XML files to understand and modify the leg39 model.

I started with the leg39.osim file:
1. what does it mean: <location_in_parent>?
2. What it is: <natcubicspline name="">? after we have a lot of coordinates (probably necessary to define the spline curve) but they are referring to the movement of the muscle attack points?

leg39_controls.xml file:
1. what does it mean <optimal_force>?

I am also looking to find the meaning/definition of much of the XML code in the gait2392.osim file. I am particularly looking for <CoordinateSet> name =""> as well as <CustomJoint>, <WrapObjectSet>, and <TransformAxisSet>. I am not familiar with XML but am trying to understand how the joints are defined and oriented.
I am working on a leg press model now but am also interested in creating a leg extension model in the near future.

I understand very well you. It's difficult rebuild the logic behind the opensim model and make the right modifications ; if someone don't tell us something more, it's a almost impossible work.

I'll keep you informed on my progress, I opened a project page about leg extension.

All,

The <location_in_parent> values specify the location of the joint center in the parent body's reference frame, and the <location> values specify the joint center in the child's reference frame.

The <natcubicspline name=""> tag is probably a placeholder to something that can take a cubic-spline function so you can ignore it safely.

<optimal_force> for an idealized torque is the maximum force that the torque can apply.

Hope this helps,
-Ayman

I found this:
<Force name="default">
<body_A> </body_A>
<point_A> 0.00000000000000000000 0.00000000000000000000 0.00000000000000000000 </point_A>
<direction_A> 1.00000000000000000000 0.00000000000000000000 0.00000000000000000000 </direction_A>
<body_B> </body_B>
<point_B> 0.00000000000000000000 0.00000000000000000000 0.00000000000000000000 </point_B>

what does it mean? why we have 1 in direction_A?