Hi All,

I am trying to make a ball float on the surface of a flip tank.

I create a default FLIP tank.
I create a default sphere and move it above the tank.
I convert the sphere to a RDB object.
I dive into the AutoDopNetwork and set the Feedback Scale to 1.

I run the sim and the ball does not float, it just falls through.

I read that the Feedback scale is what causes an object to float on the surface of a fluid, but these posts were years old and now that H14 is out the same trick does not seem to work. I have tried larger numbers and smaller, negative, numbers and I still get no floating effect.

Are there other settings I need to change as well?

Yep: you have to change the density of your RBD object. Put a lower value as 500 and this should works with no problems

Set particle Separation to 0.15 and Feedback Scale to 2 and you can see floating sphere. Default particle separation (0.25 from shelf tool) is too sparse.

Actually if you double the Feedback Scale from 1 to 2 or half down the Density of the object from 1000 to 500, you'll have the exact same sim.
It seems like one it's kind of a general scale, and the other a “per Object” … interesting

Thanks to all. I tried the suggestions and they worked.

So what are the units of the density? Is it just a made up number or is it supposed be a specific weight?

AFIK it's just a relative value. As you can see the default water Density is 1000 so you can tweak the others as you need with that in mind.

I assume Houdini uses a physical model. Your default preferences calculates mass in kilograms. I wonder if this is true…

density = mass/volume