Problems with Vertex Animation Fluid

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I’m using Houdini 17.5.327, version 1.201 of the Game Development Toolset (installed through the shelf), and a new Unity 2019.2.6f1 project with LWRP chosen at project creation time. I’ve successfully exported a vertex animation of a soft object (the obligatory cloth-falling-on-pig-head) to Unity without trouble, but my attempt at a fluid animation isn’t working - for the fluid animation I created a sphere source and used the PyroFX Billowy Smoke preset, converted the smoke volume to a VDB, and the VDB to polygons . When I export it with the VAT 2.0 ROP, the result is recognizable, but full of noisy, flickering triangles, which can be seen in Houdini even before exporting (by double-clicking the ROP) .

Any suggestions?

Many thanks,
Tim
Edited by tshead - Oct. 1, 2019 01:52:10

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Screen Shot 2019-09-29 at 10.44.13 PM.png (2.0 MB)
Screen Shot 2019-09-29 at 10.45.07 PM.png (2.1 MB)

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FWIW, I'm seeing something similar (with fluids specifically) moving into UE4. Broken triangulated meshes flickering all over. Walking through old GDC demo content (exploding pig head plume) and cannot understand what is off. Any insights on what to investigate next are always appreciated.

#1 - weird triangly mess
#2 - orig piggy plume example

Houdini 17.5.287
GD Tools 1.201
UE 4.22.3
Edited by peternicolai - Sept. 30, 2019 18:02:25

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VAT_compare.PNG (301.6 KB)

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I confirmed that I have the same issue with Houdini 17.5.391, and now that I know what I’m looking for, it isn’t a Unity problem at all - I can reliably see the behavior in Houdini directly after export, so we know it isn’t a problem with setup in Unity / Unreal.

Cheers,
Tim
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Can you try changing your target prim count and target texture size to see if that makes any difference?

If it's still not working, can you share your hip files? I've run some tests using my examples files and I'm not seeing any issues.

Mike
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Mike:

Thanks for helping out with this. I've played around with target prim count and target texture size, but the outcome is always the same - animation is recognizable, but lots of misplaced triangles.

Hip file attached.

Cheers,
Tim

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smoke.hiplc (3.1 MB)

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For what it's worth, I've got Houdini 17.5.229 and mine is working correctly in UE4. I updated my games tools shelf a couple days ago.

I recently had a problem using a fluid sim material that I'd created a while ago using Houdini's VAT output. I found that the material had been updated in Houdini, and the one I had created earlier was outdated. I seem to remember it screwing things up. When I created a new material from the new Houdini VAT output, it worked fine.

I am, however, having some other issues using the fluid sim in game.
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I need to spend some more time looking into this but I did discover that the way you're importing the volume was also including the bounding box and you were converting all 3 fields to a mesh which seems to be messing with the system. Even if I fix those 2 issues it still doesn't work as expected. BUT if I use an isooffset to generate the mesh, the exporter works correctly.

See the attached file. I'll dig into this next week.

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smoke_mike.hiplc (7.4 MB)

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Mike:

Excellent, I'm checking this out now.

Cheers,
Tim
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Mike:

I spent a lot of time futzing around with this, and it's finally working for me now, with caveats:

* In my experiments, removing the bounding box was sufficient to make things work - the VDB and IsoOffset approaches worked fine so long as the bounding box was gone.
* In Unity, things only worked for me if the texture is strictly < 8192. 8191 works, 8192 doesn't. This is with Max Size set to 8192 in the settings for the texture asset.
* I never could get things to work with the normals packed into Position Alpha - regardless of the texture asset settings in Unity, the packed normals seemed to affect the opacity of the mesh. Keeping the normals in a separate texture seems to work fine.

Many thanks,
Tim
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