B-Bone twist reverses at 180 degrees

Question Rigging

Hi, I have a question.

As shown in the attached video, the twist of the B-Bone is inverted at 180 degrees.

Therefore, the owner does not move to one side of the target.

What should I do to twist the B-Bone as in the video lecture?

Am I doing something wrong with my settings?

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Reply
  • Noritaka replied

    I took a screenshot of the target settings that might be relevant to the movement.


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  • Wayne Dixon replied

    Hi Noritaka-san,
    Interesting question.   In case you are wondering, it also skips in my demo but it just isn't as noticeable.

    The way the bendy-bones work is that it will find the shortest path of rotation.  This means that when it reaches 180 (+ or -) it will flip in the other direction because that is the shortest rotation.

    Now let's think about what's happening with twist along the length of the bone.
    If you are twisting the top - it will rotate 100%, at the midpoint it will be rotated 50%, all the way down to the other side of the bone, that will be 0%.

    So depending on where the owner bone is connected with the armature constraint along the length of the stretchy bone, this will affect the amount of rotation it will skip with that flipping.

    eg - if it's at the top where it follow 100%, it isn't going to skip any thing.

    If it's at the bottom where it's 0%, it isn't going to skip any thing.
    But as we approach the mid point of the bone, it will skip up to 50% the closer it gets to that midpoint (or 50%)

    I am finding that mathematically very interesting.  But I hope it makes sense.

    It is a confusing concept in one language, so it is likely to be even more complex if you are trying to grasp this in a second language.

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  • Noritaka replied

    Dixon-san, Thank you for your response!

    First of all, I am glad to know that it is not a mistake in the configuration, but a spec move.

    Then, as for the mathematical process, it was difficult for me to understand. But the hints you gave me made me realize the possibility that the position of the Owner bone has something to do with the movement of the example.

    So I checked the movement when the Owner bone was placed in various positions and rotated, as shown in the attached video.

    I will keep this spec in mind when using the Armature Constraint.

    Thank you ヾ(*´∀`*)ノ✨

    • excellent
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