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FLIP SIM- Collision and Sticking Problem

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Hi!

I'm making a chocolate dipped strawberry (strawberry model from 4dm-works.com). There are 2 problems. 

1) When the strawberry falls into the chocolate, the FLIP is using both bounding box of the VDB and the VDB for its collision, creating this box around. VDB resolution is at 0.007 and uniform division for collision is at 500. (which I thought are high enough?) so I'm not sure what's up.

2) The 2nd problem is that the chocolate doesn't stick to the strawberry. I have the friction, viscosity, density and stick on collision on, but nothing's been happening. I have a feeling it's something super minor somewhere.. but I can't seem to figure it out.

 

How can I fix this? (Bound_Stick_Question.hipnc)

Thank you in advance for taking a look at it!

-Y

bound_question.thumb.jpg.f9e8d2fba4ada591891bd877f9edd1f6.jpgbound_question_collision.thumb.jpg.93d64dd2c03dbb29deec38140eeed20c.jpg

 

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I just ran into this last week actually. Using a volume sample and pointing to a collision volume with a division size below .01 resulted in this box like error.  

It seems to only happen if the collision volume drops to a division size of less than 0.01 but otherwise is fine. I couldn't seem to get this to show up in the collison display or trouble shoot it. 

If anyone can help I would appreciate this as well. 

 

 

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1 hour ago, Feather said:

I just ran into this last week actually. Using a volume sample and pointing to a collision volume with a division size below .01 resulted in this box like error.  

It seems to only happen if the collision volume drops to a division size of less than 0.01 but otherwise is fine. I couldn't seem to get this to show up in the collison display or trouble shoot it. 

If anyone can help I would appreciate this as well. 

 

 

That fixed the collision problem for me, what you said about the division size. That is super good to know, thank you! The fluid still isn't sticking to the geo lol but solving one problem at a time is a good progress! I might just restart the project and see if I missed something.

 

1 hour ago, Drughi said:

It needs more exterior band voxels.

Also good to know, as I never even thought about that lol.. I'll keep that in mind for the future troubleshoot! Thank you!

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The exterior band voxels are not only important for the collisions, but also for the sticking. You should add more resolution, increase the exterior band voxels and tweak the sticking settings.

 

 

Stick_Fluid_odforce.hipnc

 

output.gif

Edited by Drughi
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That is a nice example file.

Do you have any tips on keeping some of the fluid "stuck" to the collision object. I would like the strawberry to be coated in chocolate, even after it spins around and throws some of the fluid off to the sides. I tried increasing Surface Tension and Viscosity, but the fluid still won't stick?

 

Are exterior bands the same as narrow bands? I'm not really sure where that setting is located?

 

I noticed the solver is unlocked in your example. Did you make changes to the solver itself?

strawberry_dip.gif

Edited by Atom

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Exterior band voxels are from the colliders vdb. If the voxelsize of the collider is really small the "padding" - exterior band voxels need to be increased for collisions and also the sticking to work correctly.

In my example file I have only a very thin narrow band for better speed. If you do somthing other than testig you should increase it a bit.

I unlocked the solver only to enable opencl and to visualize the sticking.

You could try to increase exterior band voxels even more. To only have it collide small padding is ok, but for the sticking it not only needs to know if fluid is inside of the collider, but also if it is close to the collider - this is where the exterior band voxels are really important to give it this padding and ability to check if the fluid is close.

I will give it another test and try to make it stick more.

Edited by Drughi
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Thanks for the additional information. I can see the exterior band voxel bounding box change, when alter the value. I never really played around with that.

Getting closer, though.

strawberry_dip.gif

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On 29.10.2019 at 12:36 PM, Drughi said:

The exterior band voxels are not only important for the collisions, but also for the sticking. You should add more resolution, increase the exterior band voxels and tweak the sticking settings.

 

 

Stick_Fluid_odforce.hipnc

 

output.gif

Hi! Why fluid density attribute so big (770000) and why decreasing this to 1 completely ruining sticky effect? Thanks

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