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Thread: Bullet objects hanging in mid-air when supporting object is shrunk!

  1. #1
    Registered User Ocyrhoe's Avatar
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    Bullet objects hanging in mid-air when supporting object is shrunk!

    I'm experimenting with Bullet and trying to get a feel for it. A "problem" has cropped up and I don't know if it's a bug or I'm just being stupid.

    I have a very simple scene: a small "person-sized" column sits on a ground plane. The plane is static: the column is kinematic. Suspended a meter above the column is a flat, square cloth (deforming object). I run the scene and the cloth drops and drapes nicely over the column, table-cloth style. So far, so good.

    I then shrink the column until it's about 20% of its original size. But the cloth doesn't follow it down: it remains suspended in empty air as if Bullet cannot recognise the change in size of the column. I tried changing the column to a Rigid body, but the same thing happened.

    Ultimately, i wanted to do a short fantasy scene where a character shrinks to the size of a mouse and gets buried by his cloak

    Does anyone have any suggestions - either what is going on, or how to overcome it?

    Many thanks
    "The trouble with doing anything right first time is that no-one appreciates how difficult it was."

  2. #2
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    It doesn't work with scaling. You could move the column downwards, this would be recognized by Bullet.

  3. #3
    Registered User Ocyrhoe's Avatar
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    Ah, thanks for that. Drat! ^_^

    I guess I can work around it (five or six "invisible ping pong balls" to "puppet" the shape). Not very elegant though. Oh well. "Newtek, I have a suggestion..!"

    Thanks again!
    "The trouble with doing anything right first time is that no-one appreciates how difficult it was."

  4. #4
    Vacant, pretty vacant pinkmouse's Avatar
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    Could you just save the initial drape over the full sized figure as a transformed object, then reload that with a smaller figure, run Bullet, tweak to get it looking how you want, then just keyframe scale the smaller figure to suit the collapse?

  5. #5
    Registered User Ocyrhoe's Avatar
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    Thanks! I think there are a few ways to do it - save trans object is a useful feature - but at least now I know I wasn't doing anything daft! ^_^
    "The trouble with doing anything right first time is that no-one appreciates how difficult it was."

  6. #6
    Vacant, pretty vacant pinkmouse's Avatar
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    Quote Originally Posted by Ocyrhoe View Post
    ... but at least now I know I wasn't doing anything daft! ^_^
    Bullet does that to me as well!

  7. #7
    Registered User Ocyrhoe's Avatar
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    Ah-ha! Some progress, thanks to some very useful new information in the documentation that came with the 11.5.1 update! It seems that if you want cloth to perform properly with any kind of deformation (bones, morphs, etc), the object the cloth reacts to has to be a deforming object as well! Scaling is a deformation - and an initial trial was very promising. The scaling might need to be done with bones, as my test object reacted a bit weirdly to being scaled, but it was enough to prove the concept.

    If the object is required to be a solid, just set shape-retention and all related values to 100%

    As a famous quantum physicist once said, "I still don't understand it, but now i don't understand it on a higher level!"
    "The trouble with doing anything right first time is that no-one appreciates how difficult it was."

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