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Thread: Bullet: Is it possible to set a start frame or equivalent?

  1. #1

    Bullet: Is it possible to set a start frame or equivalent?

    Bullet is calculating dynamics for my entire scene, but I only need simulations between a specified number of frames. Is there a way to force bullet to be dormant for outside frames?

    The closest thing I can think of is linear/angular speed thresholds... they don't seem to be having the effect I want though; it's still calculating even with higher settings.

    Note that this is for a deforming body.
    Last edited by Ryan Roye; 03-27-2014 at 11:10 AM.
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  2. #2
    RETROGRADER prometheus's Avatar
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    You have activation, start sleeping, and it will only start to deform upon impact.
    you have activate on last key,(which in principle is to start by frame) and if you set a keyframe on the deform body, it will only start to deform at that keyframe.
    you can also probably use envelope keys for some stuff, but it will take more work.

    Michael

  3. #3
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    I'm also running into this problem using dynamics with mocap data... Frame 0 is a standard T-Pose, and Frame 1 is in a different position, pose, etc... The dynamics are going all haywire. Frame 1 looks like a picasso painting, and frame 2 looks like a porcupine exploded.

    Did you manage to get this to work for you chazriker?

  4. #4
    Robert Ireland bobakabob's Avatar
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    Quote Originally Posted by samscudder View Post
    I'm also running into this problem using dynamics with mocap data... Frame 0 is a standard T-Pose, and Frame 1 is in a different position, pose, etc... The dynamics are going all haywire. Frame 1 looks like a picasso painting, and frame 2 looks like a porcupine exploded.

    Did you manage to get this to work for you chazriker?
    Could you start the simulation from frame 2?
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  5. #5
    I later found that while you can have bullet elements "sleep" between frames, it still must look at and calculate everything in the scene even if nothing is happening with dynamics. In other words, the calculation will go much faster, but the further away from frame 0 the playhead is, the longer changes will take to make due to calculating "inactive" elements in the scene. It is a severe limitation of bullet that I hope will be lifted in the future.
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    It's getting better! I changed all my surfaces to double-sided, and added a keyframe to frame 2 as well. Since the activation is after last keyframe, it's holding together, mostly. I think I just need to tweak some of the parameters now.

  7. #7
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    So in Lighwave 2018, you can set the World "Start Offset" frame for Bullet to whatever frame your "last keyframe" is on. This will make it not compute the simulation until that offset frame is reached, drastically improving the calculation time and performance for long scenes. It's in Bullet settings, on the Global tab.

  8. #8
    Registered User ianr's Avatar
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    Ask LW3dG to have word with Ewrin Couwins, Bullets main author its a long time

    Erwin updated Bullet on a major Rev ? It's @ rev 2.88 with PyBullet soon so you

    will able to run robo spiders about etc soon. But Newtek have heft to ask him .

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