stretchable bones...

[uglycat]

hm.. this is hard to explain, but bear with me.
what i'm asking doesn't involve the stretch modifier.

basically, i was wondering if it's possible to have bones that can change their length, depending on how far their child bone is.
so, say you were making a worm type mesh, and you wanted the mesh to be able to expand and contract longitudinally. is that possible? or am i resigned to use the stretch tool/modifier?
if i am, is there a way to make it so that when i stretch one bone, it does not stretch all the other bones attached after it?

[Clalan]

creating stretching bones if fairly easy, creating a stretching hierarchy with an intuitive control setup a bit more challenging. the most common way to create a stretching bone is through constraints:

- create a helper and align it with the child bone, this will be used to move the child and stretch the parent.

- position constraint the child to the helper. now move the helper and you will see that the parent stretches, but doesn't change it's orientation causing the child to "break off".

- create a lookat constraint on the parent bone, with the helper as target. now move the helper and you will see that bone is stretching like it should!

remarks:

* a lookat constraint leaves one degree of freedom, the bone can still turn around it's x-axis. you can control this by setting the upnode for the lookat constraint (default is set to world).

* this setup is only the first stone in building an easy to control stretching hierarchy. you could create an entire hierarchy and then path constraint the helpers to a spine, creating a sort of stretching spline IK!

* you can also do the same through scripting by changing the bone.length value, but it's just easier with constraints

anyway, I hope this is a good starting point!

[uglycat]

i just wanted to reply to say that the method worked very well!
thanks a lot for the help! ^_^