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I know there are already questions about this but I don't think there quite available in 2.8 blender. I want to rotate the bone so the bones will be lined up in a straight axis. How do I do it?

  • $\begingroup$ Please don't asked the same questions multiple times. If you need to edit the question you can use the edit link under it. $\endgroup$ Dec 29, 2019 at 13:03
  • $\begingroup$ @RayMairlot Yeah I didn't know how to delete my question.. $\endgroup$
    – 김준형
    Dec 29, 2019 at 13:09

2 Answers 2

  1. Go into edit mode.
  2. Select the tip of the second bone and snap the cursor to it. ⇧ ShiftS
  3. Select the root of the first bone and extrude a new helper bone from it. E
  4. Select the tip of the helper bone and snap it to the cursor. ⇧ ShiftS

step 1-4

  1. Select the helper bone.
  2. Choose the normal orientation for transformations.
  3. Create a custom transform orientation from the normal orientation.
  4. Delete the helper bone. (We have the custom orientation from the root of the first bone to the tip of the second bone, and that is all that we need.) X
  5. Choose the 3D Cursor as Pivot Point. . / numpadperiod
  6. Select the root of the second bone and scale it to 0 on the custom XZ axis, by pressing S[⇧ ShiftY]0. (Shift has to be held while Y is pressed, this constrain scaling along the XZ axis of the custom transform orientation.)

steps 5-10

  1. Copy paste the roll property from one bone to the other.

copy pasting roll

This answer expands on how the custom transform orientation works.

  • $\begingroup$ Thanks for all, but what does 'transformation' do and what is happening when I'm setting it to 'normal' and creating another one? $\endgroup$
    – 김준형
    Dec 29, 2019 at 12:36
  • $\begingroup$ Does the explanation in this answer help? $\endgroup$
    – Leander
    Dec 29, 2019 at 12:47
  • $\begingroup$ Yes it did helped a lot $\endgroup$
    – 김준형
    Dec 29, 2019 at 12:54

I'm supposing you have two copy rotation constraints, so that rotating the first bone will cause the rotation of the two others also; but the finger is deforming weirdly. This is not a problem of location and alignement of bones, but to their roll instead (rotation of their longitudinal Y axis in edit mode).

So, this is a good procedure to set up your rig: select an edge loop in which you want the rotation to happen and press Shift S "Cursor to selected", then select in edit mode the apprpriate bones joint and press Shift S "Selection to cursor"; after having completed the procedure for all bones joints you will have the bone chain that can be straight or curved, according to the mesh, but nevermind.

Activate the axes viewport display in the armature properties and adjust the roll of every bone, so that the desired "main" rotation will happen with positive X axis variations (you could use Z also, but positive X is an accepted convention).

In this way you will see that the behaviour of the rig will be as expected, even if the bones are not aligned in a straight line.

Then, if you really want to align your bones, Leander's answer is perfect.

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  • $\begingroup$ Ok, I fixed the rotation by editing the W rotation(while in Pose Mode) at the tab on the upper right. But the even after I fixed it, the Copy Rotation restriction isn't working properly. I tried checking only the X check box at the Copy Rotation config panel and the Z but nothings getting better.. $\endgroup$
    – 김준형
    Dec 29, 2019 at 12:33
  • $\begingroup$ You have to fix it in edit mode, with the roll value: editing W rot in pose mode is posing, it's not setting the rig. In this kind of rig you should use XYZ euler rotation instead of quaternions, it makes more easy to understand and edit. $\endgroup$ Dec 29, 2019 at 12:41
  • $\begingroup$ Thanks for the comment, but I don't think I'm getting what you're saying... The pose mode view is different from that of in edit mode and is the same with object mode. Shouldn't I change the pose mode? Plus I tried tweaking in edit mode either but seems no improvements has been made. $\endgroup$
    – 김준형
    Dec 29, 2019 at 12:57
  • $\begingroup$ In edit mode you build the rig in a way in which it will be the "rest pose": this rest pose will not deform the mesh. Then in pose mode every rotation of a bone will be reflected in the movements of the mesh. Bone costraints work in pose mode (and in your case they should be set in local space, so rotating in pose mode the first bone along its local X axis will be reflected in rotating the second and third constrained bones along their local X axis). This is why if the second bone's local X axis is different than the first, its constrained rotation will be in an unexpected direction. $\endgroup$ Dec 29, 2019 at 14:00
  • $\begingroup$ Now I understand about it Thank you. However for some reason nothings working. Here's my setting:. imgur.com/a/DL6PnTF If you're busy you may not answer this.. I'm such a noob so I have so many questions.. sorry. $\endgroup$
    – 김준형
    Dec 29, 2019 at 14:29

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