I've got a chain of inverse kinematic a bones, and I want the one that I grab to be unable to rotate while it is moving. How do I do this?

My setup is a rigged car assembly arm: http://sendvid.com/8z51fsgm

When I move it, the end of the arm points towards the cursor rather than simply translating up/down/left/right like a real arm. Example: https://www.youtube.com/watch?v=xglALqtKGAc

Notice how the arm's grabber tool never rotates absolute to its surroundings. The rest of the arm knows how to rotate in such a way that the tool never has to. How do I do this in Blender?


There are two ways that you can do this. You can either select the bone and add in rotation constraints or you can do it a really easy way. Simply select the bone you want not to rotate while in pose mode. Then press N to bring up the additional menu on the right side of the view port. The top tab that says transform is what you want to look at. Where is says rotation, select all of the locks and this will prevent that bone from ever rotating. enter image description here Hope this helped!

  • $\begingroup$ But do you know how to simply move the bone without it rotating? I know it's possible to disable its rotation entirely but I just want to be able to move it without its absolute rotation being affected. The bone points at the cursor when I grab it and drag it, but I'm looking for a way to have the bone translate up, down, left, and right without its rotation being affected and the bone before it only pointing at its head. Is there a way to do this? I still want the rotation to be enabled but for it not to be affected when I grab it. $\endgroup$
    – Sanix25
    Mar 10 '16 at 20:14
  • $\begingroup$ Is the bone you are trying to move connected between two bones already? And you said that you have it in an IK format so if you are doing something like an IK tail like on a dog then it will be impossible to not move bones in the middle of the chain and only certain bones. The only way to do this is if you made it an FK rig and probably un-parented all the bones in the chain so you can move them separately. Can you post an image or gif so I can better understand your question? $\endgroup$
    – Mason
    Mar 10 '16 at 21:13
  • $\begingroup$ This is my problem: sendvid.com/8z51fsgm I'm trying to make a robot arm, but I can't move the bones with any real precision because they rotate towards the cursor and point at it rather than simply translate up/down/left/right. Real assembly arms move their ends like they are translating, without rotating. Here's an example: youtube.com/watch?v=xglALqtKGAc $\endgroup$
    – Sanix25
    Mar 10 '16 at 23:14
  • $\begingroup$ Okay. I think I know what the problem is but would it be okay if you let me download your rig so I can see the settings you have on the bones and see if I can figure it out. If I do figure it out I'll let you and delete your rig from my computer. It's up to you. $\endgroup$
    – Mason
    Mar 12 '16 at 14:21
  • $\begingroup$ I actually worked it out last night. I stopped trying to use limit rotation constraints and realized I could use the copy rotation constraint on another bone in the same armature that controls the X rotation of the arm. Here's a video: sendvid.com/3my4vt8j $\endgroup$
    – Sanix25
    Mar 13 '16 at 1:23

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