How to use .BVH file format with AnyBody?

Main Forum
21

Hi,
I guess it will be not so easy to get good results in the neck/shoulder region. You can use the Vicon to validate the FAB system. The Vicon system should give you ok results.
I’m quite sceptical on the FAB approach. As you know its crucial for an inverse dynamics system like ours that the input motion is of high quality.
Best regards,
Sebastian

22

Dear Sebastian,

We really need to simulate the model with BVH input once to see what we can get from the output from AnyBody.

If you have time recently (next week is also fine), could you please have a look at my last attached neckbending model? I am also working on it now. If I can get some better results, I will update the model and let you know.

Much appreciated! Thanks a lot!

Cathy

23

Hi Cathy,
I changed some things: First I included a full set of drivers for the bodymodel.
Then I created two new classes, one which couples only rotations between the bvhmarker and the body marker and one which has hard constraints (these have to be fullfilled, instead of a normal marker definition of soft contraints). The model is running, maybe not perfect, but I guess you can do some optimisation on it. Up to now I have only included the Trunk and Pelvis markers. Please include the markers one-by-one and remove the according joint drivers to keep the model always running, otherwise its impossible to debug.
I hope this helps.
Best regards,
Sebastian

24

Hey, Sebastian,

I worked with the model.
I changed the CreateMarkerClassFixed RightArm to CreateMarkerClass RightArm, (it also worked fine), and added CreateMarkerClassTD LeftLeg and RightLeg without removing the right/left knee drivers, the model can run smoothly.
If I removed the right/left knee joint drivers in TrunkDrivers.any file, the model cannot work.

My questions are:
(1) I know the classes differ in CType = {soft, soft, soft} or not, but I didn’t see any difference between using CreateMarkerClass RightArm and CreateMarkerClassFixed RightArm.

(2) You used CreateMarkerClassRot for Head marker in bvh, because SkullThorax has rotational measure, right? Can I use this marker class for all head/neck movements, like neck bending, or rotation, or flexion/extension? Any other else markers need to use this marker class? (I guess Head is the only marker that needs to use Rot class, correct?)

(3) I added the RightLeg and LeftLeg in the model setup, but the model failed in running kinematics after I commented out the knee drivers. The markers’ sRelOpt were already made very very close to the bvh joints. Any suggestion?

Since I met the problem (3), I cannot go any forward.
Please advise when you are free.
Thanks so much for your patience and time!

Cathy

25

Hi Cathy

I will try to answer your questions, i am not so well into this model though…

  1. Depending on the amount of over determinancy in the model there might be no differences in the results if you use a hard or soft constraint. Only in the cases where there are multiple drivers for a dof. you will see a difference.

  2. when trying to drive a model using bvh data there will always be problems at the end of the linkages such as head, hands, feets. For these segments you will need to use rotational data to ensure the motion is described. On top of this there can be similar problems for stretched limbs when the elbow is entirely stretched you may also need rotational information to determine the motion

  3. what is the knee ankle in the first time frame? is it close to being fully stretched? then you may need rotational drivers.

Best regards
Søren

26

Hi, Søren,

Thanks for your reply! We will try to figure it out based on your advice.

Best regards,

Cathy