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Physics bounce (hair, clothes) *sometimes* - how to avoid?

Discussion in 'Virtual Production' started by akent99, Oct 4, 2021.

  1. akent99

    akent99

    Joined:
    Jan 14, 2018
    Posts:
    588
    I am creating short video clips to stitch into a motion comic. Sometimes clothes or hair jump around a lot at the start of the clip. (I am using the new Sequences and hence Timeline support.) My solution has been to start the recording track a few seconds into the scene so all the bouncing can settle down, but it's a pain - especially as you have to move everything if you did not leave enough time at the start. Is there a better solution? I don't understand why it happens sometimes and not others.

    Two example video clips. First one the hair bounces a lot at the start.

    https://extra-ordinary-web-stories.web.app/bugs/physics-bounce/ep1-20-050.mp4

    This one clothes of one character bounces a lot, but notice the hair from the character in the above clip this time is fine! I have not worked out why sometimes there is bounce and sometimes none.

    https://extra-ordinary-web-stories.web.app/bugs/physics-bounce/ep1-20-080.mp4

    Updated: Oct 7: Updated the URLs to the buggy video URLs. I was refreshing the other URLs with corrected versions so you could not see the problem any more.
     
    Last edited: Oct 7, 2021
  2. akent99

    akent99

    Joined:
    Jan 14, 2018
    Posts:
    588
    Some screenshots (I thought I put them in already). What I wanted:
    upload_2021-10-7_11-27-31.png

    What I get at the start of the video.
    upload_2021-10-7_11-28-17.png
     
  3. SussyBaka09

    SussyBaka09

    Joined:
    Nov 29, 2021
    Posts:
    1
    It uses numeric springing to achieve the spring effect, where both bone positions & rotations are being sprung.

    There's a stiffness setting (defined as a curve from root bone to leaf bones). With 100% stiffness, bone positions are adjusted towards parent & children post-spring to maintain inter-bone distances; spring velocity components parallel towards parent & children are also removed. For lower stiffness percentages, the 100% effect is applied partially.

    There's also an animation blending setting (also defined as a curve down the bone chain), where the user can adjust the transform blend between the bones fully simulated by springs and the original bones. This can be used to gradually blend from animation-driven to simulation-driven from the root bone down to the leaf bones. This can also be used to smoothly ease in/out the procedural bouncy effects in-game as desired.

    Here are the remaining things I'd like to implement before pushing out the update:

    • Integration with the rest of Boing Kit, so effectors can come into play and push/pull the bones around.

    • Collision components that can prevent the bones from clipping into certain geometry, e.g. prevent hair to clip into characters themselves.

    • Apply procedural scales to bones in order to achieve squash & stretch effects, maintaining object volume.