Scaling The Bullets Dynamically

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Free Tutorials

Today we scale live dynamic objects and make the scaling affect the running sim. You’ll gain some insights into how the Bullet solver inside of Houdini works and how it operates more efficiently using packed primitives. Manuel goes over the ins and outs of modifying a Bullet sim dynamically.

The problem with modifying the intrinsic transform of dynamic Bullet objects is, that Bullet does not update it’s collision geometry accordingly. Using a trick we make it think that it deals with new objects and thus reconstructs its collision hulls.

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  1. Hi,
    The VEX from, I was stuck in error. I’m probably putting something wrong but I do not see it. can you pass it to me via email “from VEX 16:34 end ?
    so just I copy it and I paste it .

  2. Hi Alfredo. Just download the project file linked above.
    Best Manuel

  3. Hi Manuel, I think the weird behaviour at the beginning where the orient parameter being left on seems to blow apart the simulation might be because the attribrandomize node is creating non unit-length quaternions. If you normalize in the attribrandomize that behaviour seems to stop and you don’t have to remove the orient attribute.

    • Thank you Julian for this insight. Makes total sense. Again I know why I prefer doing stuff myself than relying on predefined nodes like attrib randomize. But great that I now know what’s happening.

  4. Mike Jagodzinski

    Great Tutorial,

    Question tho How did you shading this scene. Im looking to try this effect .

    Any info you could give would be awesome

    • Same here, I would like to see the shading as well, perhaps using Redshift πŸ™‚

  5. Now that I have made progress in Houdini I made this tutorial perfectly, thanks Manuel was entertained and accessible you work here : )

  6. arturo valle

    the shading is passing offset to @Cd, but the thing i dont know is how they do the smooth falloff from yellow to gray passing by red, cubes just drop they values slowly, i will acomplish that in some free time

  7. Hi,
    Another great tutorial. I always learn great new things. Intrinsics are pretty cool. Do you happen to know why sidefx uses intrinsics in this case instead of just putting attrs on the prims?

  8. Noticed that a lot of your tutorials have “Oops! That page can’t be found” for the download materials. Are they available elsewhere?

    • If you let us know which tutorials are affected, we’re gonna fix the links πŸ™‚
      Thx & Cheers, Mo

  9. Does anyone know how to achieve this same shading effect on Mantra? . I’m new to Houdini and this is way beyond my knowledge. Any help would be much appreciated πŸ™‚

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