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Houdini Pyro : Nuclear Mushroom


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Studying VFX an using essentially maya and fume fx until now, i'm starting to learn Houdini.
As I'm quite new to houdini and so to pyro, I was looking for some help.

I read/listen a few tuts over the net about pyro, made some tests but I have some difficulties to get what i want.




On the one hand, the overall Idea is to create some nuclear mushroom like this one 

The thing is I do not get how to tweak the explosion shape/velociti etc. I heard (actually i read) something about some master node which set 80% of the sim (the others would be some tweak altering the master node) but did not find it. As I get it, i have to start from a fire ball in order to get the rising mushroom effect?


On the other hand, I was wondering if we could drive the smoke shape at the end in order to get a skull for example like this smoke morphing here 



Thanks for advance, any tips/advice/link/Tutorial is welcome.

Edited by Captain_Kiwii
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So I recently did this clip and I started out using the Side Effects Nuke asset available from Orbolt and tweaked it a bit - but their foundation for that setup is a really good example for studying and tweaking to see how to achieve variants of the mushroom shape...



And in this shot you never see the final shape, but I got it pretty funky looking, very mushroomy - here's a screencap from a lowres sim during RnD...



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I was about to link to this - but it's the wrong app I think...  :blink:  :D 

But the idea is the same, you basically need to get the directions from somewhere - in that setup I used particles, in Houdini you can pretty easily create a velocity field and then use that in a Pyro setup, basically the same technique I used here... (or in the tornado setup I posted here)



And to get the result you post in that picture, you'll also need to have the smoke (dust) expand quickly, so you get that "poof".


On a final note I'd like to further promote the technique of creating pointclouds with attributes to be used for driving particles, smoke or even debris, because it's so immensly usefull - it's basically the mother of "directable FX" which is the main purpose of Houdini in most pipelines. :)

Edited by Farmfield
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Thanks, i'll dig into it.


As for the pyro nuke, I download it and start to play with it. Try Some of the pyro shader i was working on but it doesn't seems to work (as the default shader) : It has some white Veil on it.


Default shader 





Fireball shader









Any hint about what goes wrong?

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A tip, if you still have access to 3ds Max, install 3Delight for Max - free for one 8-core machine license - and then you can export your Houdini Pyro sim's as VDB's and use the 3Delight VDB import object and render your volumes way way faster than with Mantra. The mushroom cloud and the two shockwave sim's I did for the KIZ music video were all exported as VDB and rendered out of Max using 3Delight, I would guess 5x the speed compared to if I'd done it with Mantra.






Edit: If you got Houdini FX you can use 3Delight right from withing Houdini, I run Houdini Indie so I have to run 3Delight through my old 3ds Max 2014 license... :P

Edited by Farmfield
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Good to know! I'll take a look after i'll have reinstall maya =)

I've been tweaking the nuke a little this afternoon, but I have some difficulties with the shader (does not react like my own i made it seems).

Also a lot of node seems to be locked, what node should I tweak to play with the overall shape/retime it/tweak the smoke etc?

Thank's again ;)

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The more, the merrier!

Great, more links and help, thank you =D

If you don't mind i would love to look at your file, the more exemple i have, the easier it is to understood how this machinery is working ;)


Let's read the topic.



Edit : Some good reading is waiting for me I would said! Thank's again, seems really interresting.

Edited by Captain_Kiwii
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Unforgettably rude, Diego, I will immediatly unlink you at LinkedIn. :D


LOL, to be honest, your post confused the sh!t out of me at first as I mistakenly clicked your link in my subscription mail as the one to bring me to this thread, but instead I came to your thread, a thread I didn't subscribe to - but was about the same thing. So I started scrolling but nothing matched up, I got seriously confused. So I took a bath and now it's all sorted.


Seems Archimedes had all this figured out 2000 years ago.  :D




Just to add something many miss - if you want to have a huge realistic explosion, you need to use the right metric for it, so match it up with the scale. If you haven't messed with it, the Houdini units are meters, so set it all up so your fireball gets into that 300-500 meter ballpark, and you'll have the correct ratios for air resistance, gravity, smoke viscocity and everything else the godlike mathematicians at SESI included in their equations, creating these gas solvers that are the foundation of the PyroFX system... You won't get big explosion dynamics in a sim that is mathematically 4 meters wide in the Houdini 3D space.  :)


And this is kinda weird if you come from FumeFX in Max as that system is build around tweaking your way to a realistic result without any real bother about scale or such, or as I heard Allan McKay say often in his FumeFX tuts, "I'm punching in numbers I know work." In Houdini the numbers you'll know works are the ones you are after. Keep to correct scale and you will get a lot of realistic behavior out of PyroFX, "for free", so to speak.

Edited by Farmfield
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