I'm using s Spline IK system to create the spine for a creature I'm making, but when I activated the Spline IK, some parts of the same seem to shrink or shift a bit. Which slitghly deforms my mesh a bit without even moving any bones.

enter image description here

Here is a GIF showing what I mean: https://www.dropbox.com/s/kmycz5s1ddka5cu/IK%20shift.gif?dl=0

Any idea on what might be causing this?

  • $\begingroup$ Please show your work in the question if possible. Screen capture or gif or etc. $\endgroup$ – atomicbezierslinger Aug 1 '18 at 15:00
  • $\begingroup$ Gif is on that link. $\endgroup$ – Pherion Aug 1 '18 at 15:14
  • $\begingroup$ You can still take the effort to place an image in your question. $\endgroup$ – atomicbezierslinger Aug 1 '18 at 15:19
  • $\begingroup$ How do you post a picture here? I didn't saw any upload button. $\endgroup$ – Pherion Aug 1 '18 at 15:22
  • $\begingroup$ Edit question. Header will show mountains and sun for image. You may comment if you do not find within 33 seconds. $\endgroup$ – atomicbezierslinger Aug 1 '18 at 15:35


Make sure

  • Align origins of curves with Snap the first vertex position of curve.
  • you have not repositioned the bones when you want to see standard rest position.

I believe you should either have

  • Separate Back spine concept and Separate Tail concept for Control concept. Fresh Start. Clear preference.
  • Switch direction of spine bones. Less Preference.

The neck bones are reasonable. The spine/tail bones are Blender Bites Ya. Your current spine/tail is like the undesirable metaphor about the tail wagging the dog. Note that I do not want address unrelated topics if possible, but this issue appears large.

Make sure you have not moved any bones in pose mode for the particular frame. The point of pose mode is to place bones in different positions.

You may need to use Menu ... Pose Clear Transforms Location. You may need to delete any keyframes.

enter image description here

Use the setting

Chain Offset enabled in the Bone Constraint Panel. This will maintain the position of the root of the first affected bone. The first affected bone will be the bone further up the parent chain as determined by chain length.

enter image description here

Successful use of Spline Constraint. Image above.

Additionally For Precise placement in a different manner be very aware of your origin on the curve.

enter image description here

Align origin to first point on curve. Snap is used for precision. Image above.

Curve origin should be first point on curve. Be precise with the use of [Snap]. Edit mode curve, Select first point, snap cursor to selected, object mode, Transform Origin to Cursor.

It seems seems you made an effort to align with eyeball which is semi precise. Snap is 100% precise.

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  • $\begingroup$ The correct steps have been shown above. Well perhaps attempted. $\endgroup$ – atomicbezierslinger Aug 1 '18 at 15:33
  • $\begingroup$ I have use snapped. In fact, the neck on this character has a IK Spline Spine working perfecly. Now the one that controlls the spine and tail is what causing the shifting. If you want I can share the blend file so you can have a look. $\endgroup$ – Pherion Aug 1 '18 at 15:35
  • $\begingroup$ No bones have been moved in pose mode, I made sure of it. And there are no keyframes. I'm the in rigging process, no keyframes whatsoever have been made. $\endgroup$ – Pherion Aug 1 '18 at 15:44
  • $\begingroup$ Okay, I rebuilt it from the ground up and now there are no issues any more. There is shifting on the back leg but that was caused by the IK on leg not having the pole target correctly set. So I'm going to assume I somehow screwed up the placement of some of the hooks somehow. This is also just an experiment, I wasn't sure if I wanted the tail and spine separate, because in reality those would be connected, so I decided to experiment with that first. But maybe it might achieve better results with the tail having it's own separate spline. But thank you for the help, the chain offset did help. $\endgroup$ – Pherion Aug 1 '18 at 16:04
  • $\begingroup$ ¿Did you switch direction of butt bones to tip of tail bones? Wagging starts at the butt under most circumstances. Unless the beast is lifting its body from tail or hanging from tail. That is another different question. $\endgroup$ – atomicbezierslinger Aug 1 '18 at 16:16

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