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Joints Shoulderproblem // Archive: Tech Forum

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Post by Tiles // May 30, 2008, 1:24am

Tiles
Total Posts: 1037
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I am at setting up my shoulder. And run into a problem here.


It works good for up and down. But with front and back it not just goes forward and backward, it rotates my shoulder too. Unexpected. I can of course rotate the joint by 90 degrees. Then moving forward and backward works as thought. And i am in trouble with up and down :D


What i search is a way to reorient the joint to act against the upper arm, and not against the shoulder as it seem to happen here

Post by W!ZARD // May 30, 2008, 3:17am

W!ZARD
Total Posts: 2603
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On the jnt limit widget is a ring which circles the selected joint - this allows you to rotate the widget to your prefered orientation. I think the joint limit widget is a beautiful piece of code - it's stable, it's flexible, it works extremely well and gives total control over setting the joint limits. If it has any drawback at all it's that it's too useful and it can be easy to get confused particularly when setting up full motion joints - such as the ball joint at the shoulder.


The approach I use is to set one joint parameter at a time like this - activate jnt limit widget for left shoulder and set only the up and down motion range. Go to opposite shoulder and set only the up and down motion so that each jnt widget mirrors the other. Then set forward and backward motion range for one shoulder then the other and finally set rotation values for first shoulder and then the second shoulder. I've found this approach helps me keep the motion limits symmetrical more easily than setting full values on all three motions for one shoulder and then the other.


Another technique I've found useful when setting joint limits is to quickly cycle through all the joints ensuring that the joint limit widgets are all aligned as much as possible before actually using them to set any movement ranges.


It may seem like a long way around method but I've found it really helpful and worth doing.

Post by Tiles // May 30, 2008, 3:21am

Tiles
Total Posts: 1037
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Thanks for this long explanation :)


I miss my answer though. I need the joint working in the other direction because as shown i am trapped in rotating the arm by pulling it. With the old native skeleton i reversed the joint in such a case. So that he worked in the other direction. Which solved the issue of rotating by pulling in most cases. It can be done with a double click at the center of the old joint.


How can i invert the joint with the new skeleton?

Post by W!ZARD // May 30, 2008, 9:01pm

W!ZARD
Total Posts: 2603
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Sorry I don't think that's possible at the moment - there is a known issue with limb symmetry which I understand has been addressed for tS 7.6. Assuming this has been fixed setting up symmetrical limbs should be very easy in the next release.


These issues are one of the reasons I started to use .bvh skeletons and Forward Kinetics for my anims. I have new characters to make however and I'm aiming to rig them with jhowels skeleton which is set up with both IK locks and .BVH compatibility. If this works even half as well as I expect it to I'll quite likely be rerigging (yet again!;)) my existing character meshes as well.

Post by Tiles // May 30, 2008, 9:14pm

Tiles
Total Posts: 1037
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Okay. Seems that i have to live with this issue then. I can at least rotate the joint by 90 degrees. And then the problem is not so obvious. Thanks Wizard :)
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