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GCharb

Pyro FX and Flip fluids to game engines

Hello everyone.

I am working on a short movie using Houdini at work and the plan is to render the whole thing in a game engine, either Unreal or Unity, I know my way around Houdini Engine, but I cannot for the love of Pete find a way to export Pyro FX and Flip fluids to these engines for render, could anyone tell me if this is possible, and if yes point me to learning ressources on these subjects, many thanks for any responses.

Gilles

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You're better off rendering fluids and simulations in Houdini with Mantra. I use Unreal Engine and Houdini on a daily basis and there's just no clean way to render volumes and geometry sequences. There are some kludges out there but why bother if you're starting in Houdini to begin with?

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1 hour ago, lukeiamyourfather said:

You're better off rendering fluids and simulations in Houdini with Mantra. I use Unreal Engine and Houdini on a daily basis and there's just no clean way to render volumes and geometry sequences. There are some kludges out there but why bother if you're starting in Houdini to begin with?

Hello Luke, and thanks for the quick reply!

The main reason I plan on using a game engine is speed, this project has bottom priority here and there is no way I will be able to use Our renderfarm for it, on my side I have been looking at exporting Alembic files for the fluids, but maps export is a problem so far, especially things like foam and the such, not to mention UV setup, which is a tad different then what I am used to, also looking into exporting the Pyro Fx to sequence of images and use as sprites in UE4, but I cant find much information on the subject, and to be honest we incorporated Houdini only a few months ago, we love it, but we are still learning the beast.

Edited by GCharb

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45 minutes ago, rbowden said:

In regards to exporting Pyro FX to a sequence of images to use as sprites in UE4, I suggest giving this a watch:

https://www.udemy.com/game-effects-using-houdini-ue4

Should help you a bit with getting a setup done and it has some hip files in there to dissect. 

 

 

Hello Ryan, many thanks for the reply and the link, will look into it right away.

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55 minutes ago, rbowden said:

In regards to exporting Pyro FX to a sequence of images to use as sprites in UE4, I suggest giving this a watch:

https://www.udemy.com/game-effects-using-houdini-ue4

That's a good resource, those were the kludges I was thinking of (using kludge because we're talking about rendering something rather than making a video game). You still have to render a bunch of stuff to make that work though which is what the original poster is trying to avoid. If you're going to take the time there to render the sprites you might as well just render it in Mantra outright. The payoff isn't really worth it for one time use versus a game where it would get many uses.

The vertex animations in Unreal Engine in rely on consistent topology. Something like a FLIP simulation would have arbitrary meshes on each frame. To animate arbitrary meshes you'd need a different solution like toggling their visibility over time which has it's own set of issues. I get the desire to render things quickly but Unreal Engine isn't a renderer it's a game engine so the workflow and optimizations are all geared towards that. I'm using it as a makeshift renderer on some projects but it comes with a lot of strings attached.

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In one of the FLIP master classes Jeff Wagner mentions a technique where you basically sim out your fluid till it takes up all the space it is ever going to take up then you freeze that geometry. After that you can re-sim  particles moving along the surface and use those to make moving maps that emulate fluid flow. He does not really go any further than saying it is possible, however.

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The term you are looking for is flowmap and you don't necessarily need to do a sim to create one. You can do a complete sops based approach to do it but, you can do a flip sim to create one though if you really need to:

https://github.com/sideeffects/GameDevelopmentToolset

Has an example of how to do that but, I have a feeling it will become alot easier with H16.

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6 hours ago, rbowden said:

The term you are looking for is flowmap and you don't necessarily need to do a sim to create one. You can do a complete sops based approach to do it but, you can do a flip sim to create one though if you really need to:

https://github.com/sideeffects/GameDevelopmentToolset

Has an example of how to do that but, I have a feeling it will become alot easier with H16.

Yes, vector displacement maps, these should do the trick, I should have looked into it but for some reason I did not think Houdini had those, will look into how Houdini manages those, thanks a bunch for your help.

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7 hours ago, Atom said:

In one of the FLIP master classes Jeff Wagner mentions a technique where you basically sim out your fluid till it takes up all the space it is ever going to take up then you freeze that geometry. After that you can re-sim  particles moving along the surface and use those to make moving maps that emulate fluid flow. He does not really go any further than saying it is possible, however.

Thanks for the tip, will get the videos from GoProcedural.

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