Spline IK stretching when Y stretching is disabled

Okay I’m having trouble with a model I’m working on where I have a spline IK for the spine. i want as little as possible movement between edit and pose modes so I’ve move all the bones into the same position in edit mode that they go to in pose mode with the effect of the Spline IK. This is all fine until I get to the last bone, which if it sat still would actually be in the correct spot. Instead it squashes the last bone (the one with the spline IK constraint).

I created a small test with a simple Bezier curve, straightened, then added 2 bones and laid them out perfectly along the Bezier curve. Between edit and pose modes everything is still as it should be, but, if you move the tip of the Bezier curve back, shortening the line, the second bone will squash when I would expect it not to scale at all.


WHYYY.blend (454 KB)

You asked your question in the wrong section. You may have a better chance of getting one if you asked it in the Animation and Rigging thread.

Done. Sorry about that.