FLIP fluid without initial movement

[KiLa]

Hi!

If you look the attached file... I have a fluid surface which is surrounded by a static object - acting as a tank, and a sphere that is falling into fluid.

The problem is that the fluid surface starts moving before the sphere hits it.

What is the "correct" way to stop this happening?

test.hipnc

[Hudson]

Hello Kila!

You could stop it from happening by affecting particle velocity or field velocity and set it to zero. Altough it is good to know that this motion occurs because the particles are supposed to fill the tank and their initial state is just random inside the tank. Most people actually simulate a few frames before the simulation just to let the fluid settle down.

I controlled the particles velocity by switching from zero to simulation velocity at one frame. You can also do it using point clouds to see if an object is close to an inpact with the fluid and so on.

In my example file you have some particles "disapearing" that is because their vel is set to zero and if any of these particles are inside the coll they will get killed.

But I would rather say, give the fluid some frames to settle down. If anyone else knows a better solution I am glad to hear

I hope this helped

fluid_null_vel.hipnc

[KiLa]

Thx Hudson!

If i understood your setup correctly (Noobster here ), you are forcing the velocity to be 0 till frame 20.

I'm a bit surprised that we have to use VOP, in order to do this kind of , very basic scenario. The "problem" is that i know you can do almost anything in VOP, but im trying to find an option from the UI that will do it for me.

[lukeiamyourfather]

Some simulations won't look good starting with the first frame. Liquid simulations are particularly finicky in this sense. One possible solution is to simulate for a while before dropping the ball into the tank, so the fluid has a chance to settle down naturally. Then render out only the frames when the ball is dropping into the fluid.

Edited July 29, 2013 by lukeiamyourfather

[Hudson]

Now both me and Luke recommended you to simulate some frames to let the fluid settle down before your first rendering frame.

If you are still looking for a way of doing the same thing as I did in the VOP using UI. The closest I can get is in the file. But no one would use it because when you mesh your fluid you will get something rather ugly

flip_gravity_swap.hipnc

[KiLa]

Thx guys!

One "solution" was provided also here:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=134076#134076

I did not know that you dont need gravity in order to make RBD object fall

[Skybar]

I did not know that you dont need gravity in order to make RBD object fall

Well, you do. In Hudsons example he uses two Gravity DOPs, one that is always on for the sphere - and one which he activates later, that is only attached to the flip.

[KiLa]

Haa, i missed that one

Thank You!

[Effort5]

thank you very much!!~~