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[Mantaflow] FLIP particles not visible
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: AMD Radeon HD 7560D ATI Technologies Inc. 4.5.13417 Core Profile Context 15.301.1901.0

Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2020-01-06 20:54, hash: rB3a35301fd16d
Worked: (optional)

Short description of error
If you bake any liquid, after baking FLIP particles will not be visible in the 3D window. The checkmark Liquid is set. For the FLIP particles to appear, you need to click on the Liquid checkmark (the checkmark will not change its state). After these actions, particles will appear.

Exact steps for others to reproduce the error
Reproduced in any scene.

  • Default cube: Physics > Fluid > Type: Domain; Domain Type: Liquid
  • Observe that [x] Liquid appears as checked
  • Observe that, under Particles, there is no "FLIP Particles" system
  • Observe that checking [x] Liquid manually doesn't go to an "off" state but stays on a "on" state; it also triggers the creation of a particle system

Revisions and Commits

rB Blender

Event Timeline

Emir Sinan Gürlek (filibis) changed the task status from Needs Triage to Needs Information from User.Wed, Jan 8, 3:24 PM

I can't reproduce this. Baking domain works as intented and shows particles. Could you share a .blend file that is not working for you?

This error occurs in this scene:

Perhaps the problem is again in my old video card.

Emir Sinan Gürlek (filibis) changed the task status from Needs Information from User to Needs Developer to Reproduce.Wed, Jan 8, 4:13 PM

Allright this happens for me as well for this file. Unchecking and checking Liquid checkbox make the particles data appear. Let's wait for a developer to reproduce the issue.

The problem boils down to the fact that, when an oject is assigned Domain Type = Fluid, the "Liquid" checkbox appears selected even if it's not.

A minimal way of reproducing the core error is:

  • Default cube: Physics > Fluid > Type: Domain; Domain Type: Liquid
  • Observe that [x] Liquid appears as checked
  • Observe that, under Particles, there is no "FLIP Particles" system
  • Observe that checking [x] Liquid manually doesn't go to an "off" state but stays on a "on" state; it also triggers the creation of a particle system
Germano Cavalcante (mano-wii) changed the task status from Needs Developer to Reproduce to Confirmed.Fri, Jan 10, 12:44 PM
Germano Cavalcante (mano-wii) updated the task description. (Show Details)
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

Unfortunately I'm not able to fix this myself, like I wanted to.

If it helps, it looks like adding something like

RNA_def_property_update(prop, NC_OBJECT | ND_DRAW, "rna_Fluid_flip_parts_update");

to rna prop: "domain_type" would likely fix this (except this is not the right way, and for example it would break Quick Liquid, which instead works correctly right now because it calls for the update directly from Python).

I'd like to point out that this bug has a potentially very high impact on usability!

I'm worried that those who are testing 2.82 are *not* taking advantage of the FLIP particle visualization at all, because it doesn't work out of the box!

Germano Cavalcante (mano-wii) triaged this task as High priority.Mon, Jan 13, 1:47 PM

I just incorporated the suggestions from the discussion. I hope this fixes the issue.

I've tried it and it seems to work well (both manual and Quick liquid)!

Not sure who should do this, but this must be ported to the 2.82 branch too

@Nicola De Mitri (nicolasap) Yes, I accidentally committed this to master first instead of the 2.82 branch. Should be fixed now.