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Arm twist bones for Luna.

Forum Archive › Arm twist bones for Luna.

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  • December 6, 2024 at 10:11 am #19306
    Markus Schille
    Participant

      Thank you for a great learning experience!!

      I have one issue I would like to learn about. It is perhaps outside the scope of this course, but I’ll ask it anyway.

      When rotating Luna’s hands the lower arm does not twist along with it. This is consistent with the design of the rig, since the bracers should not twist or bend.

      However, in both Rigify and Blender Studios ‘Cloudrig’, the Lower Arm Bendy Bone twists along with the hand, but it keeps straight and doesn’t bend. I think this is often the desired behavior for arms, but how can I achieve this? The end handles are set to tangent as you can see here, using the ‘Rain’ character as an example:

      If I try to set the Luna rig DEF-ForeArm_02 to tangent with the hand (any hand bone) it will both bend and twist as it did at the start of the course when it was connected to the child. How can I change it so it only twists? Is it just a minor fix, or is it complex? I’ve tried to find out, but came up short.

      Below is how Luna’s wrist looks when twisting the hand and there is no twist in the arm.

      December 6, 2024 at 4:46 pm #91608
      Harris Clook
      Participant

        Might weight painting solve it? Or could the hand controls also have an increasing influence on the forearm_01 and _02 bones? Also when I twist my own wrist (my actual arm, not a 3d models) the muscles in my upper arm move too – I guess this is what makes rigging a fun puzzle to solve.

        Nonetheless I’m commenting here so I can get a notification for an answer!

        December 6, 2024 at 6:03 pm #91609
        Markus Schille
        Participant

          Hi,

          With the knowledge from this course and studying the ‘Rain’ rig, I was finally able to figure out the solution. The Ease Out setting needs to be set to 0 on the Bendy Bone towards the hand. This makes it follow only the twist, not the bend.

          I also added two Copy Rotation constraints to the center MCH-Forearm_02_tweak, followed by a Damped Track constraint towards the hand, so it rotates at 50%.

          I might try applying the same technique to the upper arm, and even the legs.

          December 7, 2024 at 4:48 am #91610
          Wayne Dixon
          Participant

            HI Markus,
            Excellent question.  And you are totally correct – when I designed the arm I remember not including the forearm twist because of the issues that caused with the bracers. (you don’t want the rigid gemstone thingy warping when she rotates her hand)

            I’m also proud that you found a solution. That’s one of the main goals that I’m trying to do with courses like this.  Give you enough information and confidence to figure out solutions.

            The best way to learn new things is to pull them apart.  Reverse engineer someone else’s work and see how they solved the problem.
            Then once you have figured it out, you can add it to your bag of tricks.

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