Nvidia Flex and Bullet solver fluid simulation quick tip - 2020-04-25 14:26

Nvidia Flex and Bullet solver fluid simulation quick tip

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This is really awesome. Thanks for sharing!
2 questions.
1- Why do many of the particles drain thru the bottom of the bounding box?
2- What steps would be required to ’ mesh’ the particles so they could be rendered as water?

Hello, thank you for the demo but would it be possible to allow full screen for the video? The image is quite small and difficult to read, thank you, Jacques

If you click on the button that says “Tutorial Link” it should take you to the Vimeo page where this video is and you can view it full screen there.

Let me know if that doesn’t work.

its ok, thank you, i can have it full screen

In flex solver change shape collision margin in to min that will stop particles drain through box,
but I am also curious about answer for 2 question :wink:

Hi all,

I have a Flex solver and Actor question, and it might be needing a trick.

  • Flex solver is accepting my EXR 32bit input texture and positions objects properly, great, love it btw
  • that’s OK when my input texture is not a video or being modified continuously by a noise TOP for example
  • Flex the Actor doesn’t want to move my object positions, it just takes the 1st pos available and ignores the incoming rest
  • do I have to pulse the Flex Actor comp at 60fps to get that animated texture input to work?
  • I can get that it’s not in Flex’s nature to do that, but is there a feature that has been integrated for that case?
  • Or a trick? So that when there is an effective collision on any element, the physics of Flex can trigger and ignore the previous animated movement?
    Cheers :), P

Hi all,

BTW, it’s at the Actor level that I have a problem, sorry for the unclear post above. Here is a screenshot comparing regular Geo instanced and Actor instanced from a 32 bit texture. What I am looking for: Flex accepting animated input (I will make sure geos don’t collide between themselves if need be). Then when another solid comes bumping against my little balls, Flex calculates collisions against everything. In other words, the animation of my little balls must stop ONLY for the balls are collided with other balls or the incoming geometry.
I am starting to wonder if I should use Bullet instead, P

I recommend checking out the Position Feedback TOP and Velocity Feedback TOP parameters on the Actor COMP.
https://docs.derivative.ca/Actor_COMP

You’ll have to update your build, the one you are using is from a few months ago and doesn’t have these parameters.

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In the case of Actor COMPs, the instance parameters define only the initial transform of the actors. Once the simulation is started the solver COMP (bullet or flex) drives the transform of the actor COMPs.

The way to override the transform while the simulation is running is to use feedbacking; in the case of Bullet this is done using the Bullet Solver CHOP and Feedback CHOP parameter, and as Ben said, in Flex we recently added support for Position/Velocity Feedback TOPs.

In your example, you would reference your movie file in TOP on the Position Feedback TOP parameter. If you only want to override some of the time then you would create a switch with the Flex TOP. Putting the Flex TOP position texture into the Position Feedback TOP will have no effect on the simulation.

Thanks a lot guys!
Happy to see it’s a feature, P

Hi all,

Just a quick general Flex behavior: my tops coming into the actor are all the same size: Color TOP and Position TOP, but I am constantly getting this error:
“all Ops must generate the same number of instances…”
It goes away when I break a few things and redo my linking bu then it also comes back, see screenshot. Best, P

Could you send your toe file so I can take a closer look?

Hi Eric,

I did the recommended update in-between and killed the old Flex Solver for a on I copy-pasted from the snippets, no more problems… apologies for this, I should’ve not posted tat.
Do you still need the file? best, P

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BTW it’s working fine now, thank you all, P