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Incorrect Mantaflow fluid border interaction when collision is turned off
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.92

Blender Version
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-06-01 20:37, hash: rB1d4bae856690
Worked: (newest version of Blender that worked as expected)

Short description of error
When you turn off bottom 'border collision' checkbox, the fluid still interacts with the border.

Exact steps for others to reproduce the error
create a cube.
Use quick effects fluid.
Set flow behavior of box to 'inflow'
Turn uncheck border collision bottom,
run simulation, see small ring form around stream at bottom.

Event Timeline

Philipp Oeser (lichtwerk) changed the task status from Needs Triage to Confirmed.Jun 3 2020, 11:19 AM

Can confirm.

I can reproduce it. However, I'm not sure if this is a bug or an "implementation detail". When you generate a mesh for the simulation, you see that those particles at the bottom, are not taken into account. Not sure if this is right, but it looks like mantaflow is not deleting the particles but keeps them lying around without further influencing the simulation.

@Sebastián Barschkis (sebbas), can you confirm that?

Yes, can confirm the issue too. While the mesh is unaffected, the FLIP particles really should not go beyond the domain borders (the "ring" from your scene is odd too).
Will investigate this issue further.

Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Bug".Jun 25 2020, 1:14 PM

Will classify as bug then.