How to get Spline IK to straighten instead of stretching ?

Support Animation and Rigging
1

Hi, I’m trying to use a spline IK to control a character’s column, what I want is that:
-root of the spline staying on the root of the column: a hook between the vertice and the bone does it
-column’s bones following the bezier curve and the tip of the curve following a lattice: the Spline IK does it
-the tip of the last bone of the column following the tip of the curve: with Y stretch it works but without not.

Then instead of stretching, is there a way to reduce (or increase) the bone’s rotation until both tips are mingled ?

Thanks

2

Not sure If I quite understand what your asking…

but will take a guess…

You want to prevent the spline IK from causing the bone to stretch versus simply rotate into place…

3

Untitled.png957×556 25.3 KB

I did these 3 examples, the first is with Y stretch, the second is without and the last is as it should be.
As you see the problem with the first is that my character will be stretched, the problem with the second is that the empty is not where the head will be. But maybe I just have to forget Spline IK…

4

Personally I’m finding the New Bendy Bones to be easier to use and quicker and simpler to setup with less problems than Spline IK… (not that I would not use Spline IK in some instances…) but so far I am very pleased with Bendies…

and for the small number of bones you have there… I surely would use a bendy… (of coarse I still haven’t seen all your project… but)

having said that…

I’m not sure using Bendies would eliminate the ‘stretch’ problem…

5

If your just looking for a nice easy to animate spline for character animation

this one has my highest recommendation…

with this Rigg you avoid the complication of Spline IK and Bendie Bones…
yet you still get a very animation friendly Spine Rigg for Character animation…

plus there is some very important Rigging concepts in the above video that if you have not run across them before you need to see them and understand them… they are ‘Very’ useful…
…

6

I don’t know bendie bones, will take a look.
Thank you for the video, mabe I will use that technics, even if my wish was to control the column by moving the head (or the top of the torso).

7

even if my wish was to control the column by moving the head (or the top of the torso).

If your not wanting to have any stretching… that may be a difficult thing to do…

You could use a ‘Limit Distance’ constraint on the Head Empty to keep it from moving too far away…

but not sure if that will give you the desired result or not…

8

I already tried that, and no, it doesn’t work because it limit the empty moves.
I will forgot the idea… thanks.

9

OKay well sorry I couldn’t help…

10

No problem…

11

Is this not a contradiction in itself?

Bones chain with no stretch have a maximum lenght, when they are straight, so thats also the maximum distance for your empty when the top of the bone chain have to stay at the same spot like your empty.

12

A question of priority I think, is you look at my picture, you see something possible.
What I ask is for the ik spline to do his job but with a priority for the top of the chain to stay to the empty.