# Loop Rotation Problem

Does anyone know how to fix the Rotation Loop problem?

It’s when you rotate a rig (Such as Root Bone) And you rotate it around at it’s pivot location all the way back to 0 making it a 360 loop.

So Frame 0 = X.Rot (0)
Frame 10 = X.Rot (90)
Frame 20 = X.Rot (180)
Frame 30 = X.Rot (270)
Frame 40 = X.Rot (360/0)

But when I hit 0, it cycles out of control in the opposite direction to reach the designated 0/Full loop.

You can see what I mean in the video.

If you want a continual loop, use (#frame/10) * 90, no?

Cool. But where Do I type all of this? in [Transform > Rotation > X]?

Alright well I typed it in and crazy things happened.

So…

My Best solution was to Select the (W) Rotation Axis and type -1.000

It works but Then you know it’s not back set to normal as in (Alt + G = 1.000)

So I would probably have to go to the next frame and hit Alt + G to make the Rot reset seamlessly.

But hey whatever. If this is the only way then I guess I’ll have to stick with it.

This is how Blender handles quaternion rotation (which is not how I would prefer Blender handled it.) It uses the sign of the W channel to indicate the direction of rotation (mostly, because it doesn’t slerp.) This means that you can have a rotation of 360 degrees or -360 degrees, and it it goes from one to the other, well, it interpolates between those two rotations.

What you can do is have a keyframe at frame 39.5 and at frame 40, so the interpolation happens between frames. But no, that’s not really ideal.

You can also use Eulers, which will let you key your frame 40 to 360 degrees and your frame 80 to 720 degrees. That’s not really ideal either-- it solves motion blur and fcurve handle problems with the quaternion solution I mentioned, but it introduces problems with NLA (and maybe with fcurve modifiers.)

Eventually, the plan is for Blender to get quaternion slerp support, at which point this stops being a problem, but who knows when that will happen.

2 Likes

Thank you I’m glad I’m not the only one with this issue.

I knew I wasn’t crazy! Lol

I really Hope they do look into this. I didn’t think it was that known.