I will try to help solve the problems
First of all the data from the motion markers are in mm. not in
so this data has to be multiplied by 1/1000 otherwise there is no
chance for the model to assemble kinematically.
The next step was to impose a set of initial positions on the model
since this is needed to make the model assemble. This needed in cases
as this where the model forms a closed kinematical chain when the
markers are to be followed.
I also added the markers initial position since they are equally
important, I have used the first number from the data set for each of
This was not enough to solve the problem.
I then looked more into detail of the model and there are a few
problems which need to be solved before the model will work.
1 . There seem to be no joint between radius and ulna ?
2. In the file Drivers.any where the drivers are made you attempt to
drive in total 13 dof. this is too many. Your model should have the
GH =3 dof
Wrist =2 dof
This gives in total 7 dof which can be driven by the markers. So you
need to remove six of the dof in the Drivers.any file, before it can
work otherwise the model is over constrained a can not assemble.
- The graphic representation of the bones that you use is not
representative with the nodes on your segments. This is in principle
not a problem you should just be aware that the bones you see in the
modelview do not represented how the model really looks. The reason
probably, that you have inserted new values for the node locations
maybe used the AnySurf files from the BRep. These AnySurf files
correspond to a specific person and the when the coordinate system of
the bones is changed (this is the case when you use new values for
sRel for the nodes defining the joints locations) you will need to
change the origin of the their insertation point on the bone and
possible also their orientation to make them fit your new points. In
the zipped file I have uploaded I the actual geometry of the bones
visible, since I have added a AnyDrawSeg line in each of the segments
in the Segs.any file.
I will suggest the following two steps procedure to resolve the
problem. I think it is important to break the problem down into
1.Make a model which is not driven by marker data, but by drivers on
the GH, FE, PS and writs joint.
1.1 Add the PS joint
1.2 Change the location of the AnySurf files so that they represents
the actual model
1.3 Add drivers for the GH, FE, PS and wrist joint
1.4 Make sure this model assemble kinematically
2 Make the marker driven model.
2.1 Add the markers to the previous model by using the
MotionTracker.any file do not add the drivers between the markers and
the arm yet
2.2 Make sure that this model run kinematically
2.3 Change the location of the GH joint so that the location of the
arm fits in the best way with your marker data.
2.4 Remove the drivers for GH, FE, PS and wrist joint
2.5 Add the drivers between the arm and the markers, but the numbers
of drivers should be limited to 7 dof. since this is the number of
in the arm. It is important to select the dof form the markerset
carefully so that descriptive dof are chosen.
I hope these steps will help you solve the problems, please write
again if you have further questions
I have uploaded the file NewApproach2.zip
— In email@example.com, “Sarah R. Sullivan” <sarsulli@e…>
> I have been trying in vain to get a four-bone (humerus, radius,
> hand) arm model to be driven by 3-dimensional marker trajectories.
> followed the sway practice model and tried to mimic mine after that,
> and have also tried to troubleshoot using help from other models,
> with no luck. I can get the model to load, but I can’t run the
> initial set-up or kinematics analysis yet. Right now, my kinematic
> tolerance appears to be too small for the job, but I have checked my
> model output and model is not overconstrained.
> I have uploaded the model and would welcome any suggestions as to
> I can get this up and running (I think I’m so close!).
> Thanks so much!