Rigging - Mesh doesn't stretch to joints

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  09 September 2012
Rigging - Mesh doesn't stretch to joints

Hello there,

I'm encountering a problem (or maybe a feature?) where with a simple spline-IK setup, the skinned mesh doesn't completely stretch up to the final joint of the hierarchy. Check the example for what I mean, if you pull the top control then the top of the mesh doesn't stick to that control point like you expect it to. With this example it's not even that bad, with something else I'm working on, the meshes don't even stay pointed at the controls and the bottom is just as bad the top. It's as if the skin is only 50% effective or something. How am I supposed to animate if I can't control my mesh completely?

Does anybody have any idea on how to fix this? I'm not big on rigging. Thanks!
Attached Files
File Type: zip RigExample.zip (70.4 KB, 8 views)

Last edited by ChrisCorr : 09 September 2012 at 11:27 AM.
 
  09 September 2012
Howdy,

The problem is that you need to include the end joint (number 5) in the skinning and have it weighted, too.

Adios,
Cactus Dan
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  09 September 2012
In the skin object set the "Length" to "Bone scale" or "Volume scale" depending on what you want.

I think Dan's explanation is close.

Joints only move points relative to the joint axis...and since there is no weight on the tip it doesn't "stretch" the mesh. (the stretching is a side effect of othe points being bound to other joints.)

Using "volume scale" allows a joint to actually stretch points that are bound to it.
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Last edited by chi : 09 September 2012 at 12:22 PM.
 
  09 September 2012
Thanks guys, but the problem in my original project was having the Jiggle deformer active on the mesh while trying to animate, apparently you shouldn't do that.

But in that file I attached, I guess I need that final joint like Cactus Dan said, although I learned from a tutorial that I shouldn't include that one. Don't believe everything you see on the internet, kids!
 
  09 September 2012
Usually you do not weight the last joint.

Since everything you do with joints comes from the axis of the joint itself the last joint often doesn't have any geometry around it that it can deform.

I will also say that weighting the last joint in your file breaks the mesh (the point jumps to unexpected location)
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  09 September 2012
Which is it then? Should one weight the last joint or not? If you weight it you have to put the skin length mode to volume scale, is that it?
 
  09 September 2012
Howdy,

Here is an example of weighting the end joint.

Adios,
Cactus Dan
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  09 September 2012
Originally Posted by ChrisCorr: Which is it then? Should one weight the last joint or not? If you weight it you have to put the skin length mode to volume scale, is that it?


It's fine either way, but 9/10 you won't weight the tip joint. Use Position Scale in the Skin Deformer like Patrick mentioned. Neither is right while the other is wrong.

But often you will not weight Tip joints.
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  10 October 2012
Thank you all for your help. Thanks for taking the time with the file, Cactus Dan.
 
  10 October 2012
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