Pyro cloud optimise refine.. caching and detail

[anthonymcgrath]

Hey everyone I've been having a play with the Pyro fx shelf in houdini.  I want to generate a big cloud going off.. pyroclastic in nature I guess. I plan on using it in a personal animation project I'm working on. I did a nice test in maya with fluids but the test results with houdini and exporting vdb are (i think) looking quite nice.  Quick Yt vid below.. the last 3 are the ones I'm happiest with.

https://youtu.be/NbxL6X2Meoo

So I basically just scale up a grid mesh and that emits the Pyro. 

However my cam angle is going to be ground level.. cam on floor nearly. So the rear half of the vdb cache is never seen. Is there a way to get houdini to make the same sort of Pyro cloud but in a lighter way.. eg not generating or processing the back half? I just need to get the cloud to come to camera really.  I've got some proxy geo in my final env scene I would like it to collide with too perhaps.

Also can anyone give me some good tips on generating detail? I think there's a subdivision value that I set to 0.05 and that took an hour and half to write out 100 vdb frames. On a tutorial it said take it down to 0.02. That would make it chug but if it needs to do so overnight thats ok.  I guess the main question is how to get more "pyroclastic" look to the cloud?

Sorry for the long post but if anyone give me some pointers on achieving this that would be great I'm quite happy to sit and twiddle values and do test caches to get it looking great!

 

[Yon]

You can use the Sink From Objects tool in the Populate Containers tab which will make your smoke disappear within the bounds of an object ( that you place behind your cloud).

You can turn your geo into a static object to collide with, or turn it into a volume and use source volume with Cource collision set in drop down menu.

mestela has a write up on pyro and collisions here http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops#Whats_needed_for_a_pyro_sim_with_collisions

The single best technique I found to get really nice high frequency detail is this, and its a main reason I always use a up-res step in my workflow;

You want to up-res with wavelet turbulence, and a low frequency scale.

The basic workflow is you cache your low res ( I usually use .1)

Then use the Up-Res Container tool in the Container Tools tab with your smokeobject node selected, and it sets the up res network.

Set Source to file and load your low res cache.

Go to shape and enable turbulence. Hover your mouse over it to read how to set the value correctly - It's one unit for every doubling.

As in if your low res is .1 and your upping to .025, enter 2 ( .25 * 2 * 2)

Then in the Turbulance tab change it to Wavelet, reduce Frequency Scale to .5 and cache that as your high res sim.

You can see test to tweak up res settings here at vimeo.com/43627398

 

And theres a older thread for pyroclastic noise here

And with up-res step, you never have to pay for high res velocity field

Edited August 28, 2016 by Yon Anadeyo

[anthonymcgrath]

Hi Yon thanks for the reply that is awesome information.  I was hoping there would be an up res mode building on general movement of a lower res one:) can't wait to try these things! 

[anthonymcgrath]

On 28/08/2016 at 1:50 AM, Yon Anadeyo said:

The single best technique I found to get really nice high frequency detail is this, and its a main reason I always use a up-res step in my workflow;

You want to up-res with wavelet turbulence, and a low frequency scale.

The basic workflow is you cache your low res ( I usually use .1)

Then use the Up-Res Container tool in the Container Tools tab with your smokeobject node selected, and it sets the up res network.

Set Source to file and load your low res cache.

 

hi Yon i gave this a try... but sadly its not working.  I dived into my pyro_sim node, then selected the smokeobject and ctrl+clicked the up-res container node but i'm just told that i have no fluid objects selected   I cant seem to get past this step :/

 

[Yon]

haha yea its a weird little thing Houdini does,

I think when you click the tool, it prompts you to select a box, so select your smoke object

and then hover your mouse over viewport and hit enter, this happens to me all the time haha

pretty sure that fixs it

[anthonymcgrath]

4 minutes ago, Yon Anadeyo said:

haha yea its a weird little thing Houdini does,

I think when you click the tool, it prompts you to select a box, so select your smoke object

and then hover your mouse over viewport and hit enter, this happens to me all the time haha

pretty sure that fixs it

yep if you hit enter when the smokeObject is selected and your mouse is in the network view then it just dives in - makes sense

however i tried hovering mouse over the main viewport after selecting the smokeObject and it still throws me the error.

I've attached the scene for you - its nothing complex, literally just made from the shelf buttons and a simple grid as an emission source :/

super_quick_pyro_test03.zip

[Yon]

ah, you must click the container tool, then select your smokeobject, hover over viewport and enter

super_quick_pyro_test03.hip

[anthonymcgrath]

aha well it seems i wasn't able to select the node, but i was able to select 'something' in the viewport as a bounding box appeared around my pyro effect.  I hit enter and its give me an uprespyro setup.

[Yon]

yea you can just select your container in the viewport also

[anthonymcgrath]

so heres what i have - on the left is my original pyro_sim setup.  I've setup the pyro_import so it reads from my .vdb file seq on disk.

the upres (i think) is now using the upres setup - when i scrub the time line both seem to update quite quickly.  I'm guessing from here now i can jump into the upres_pyro_sim node and add the turbulence and wavelet etc in there?


it was chugging at first then i realised i'd turned off the read from disk in the pyro_import of the orig sim lol! 

 

[Yon]

yea in the up res node there is a Source, change to file and bring in your low res

then in Shape enable turbulence, if your hover over it theres directions to set correct value and turn turbulence source to wavelet.

you can keep the same resolution as your low res and it will still show what wavelet does, just use like 2 as value

and frequency scale .5

[anthonymcgrath]

okay i think i'm slowly sussing out whats going on but there seems to be two options here to 'load' the low res file seq from?  I have both switched on lol - can you tell me which one i should be using please Yon?  Bit puzzled there :/

[Yon]

yea right in the bottom picture, direct to low res cache from disk

[anthonymcgrath]

Cool thanks Yon I'll have a play and get back with my results and see what happens:)

 

Actually now I see it what's the difference between the two as it seems like the two do the same thing?

Edited August 29, 2016 by anthonymcgrath

[anthonymcgrath]

nope i'm still not winning here

i've got the upres sorted out but for some reason it chucks up an error when it tries to read my .vdb sequence ?

I've attached an image and my scene file.  from what i can see i'm reading in the base resolution sim in my PYRO_IMPORT node by means of a file node.

but my error is appearing in my uprespyro_sim node (see image) - i point it to read in the file but just get an error

super_quick_pyro_test05.zip

[anthonymcgrath]

been trying all sorts here all evening and i cant figure this out at all   Yon do you have any suggestions?  I'm trying to load my .vdb into the slot but i just get a heap of errors/warnings as shown in the image above

[Yon]

I have never cached a .vdb always bgeo.sc...prob why it doesn't load

this isint such a huge step just a nice way to get fine detail

[anthonymcgrath]

ok thanks Yon i can give that a quick try and see if it brings me better results

I've had a watch through the videos on vimeo to show the different settings examples and

I would say its this kind of look i'm trying to create - the thick pyro cloud look.. in my scene i have a small T junction road with some buildings and i'd like this cloud to go off and emanate outwards towards the camera - i did a quick example (last one) in my youtube video in my first post.

here's a ref image i'd like to try and get closer too - i persoanlly think i wasn't far off but i need it to be more 'crisp' i guess - globby and bubbly like a pyro cloud.. i'm guessing the only real way i can tighten it up is to just set the division size on my original smokeObject to something quite small and leave it overnight to process :/

pyro cloud example

Edited August 29, 2016 by anthonymcgrath

[Yon]

good sims take days for a single machine

I have two computers at school always computing If I'm at home, and my workstation going if I'm at school hahaha

[anthonymcgrath]

9 minutes ago, Yon Anadeyo said:

good sims take days for a single machine

I have two computers at school always computing If I'm at home, and my workstation going if I'm at school hahaha

no worries thats what i figured hahah - did you see that video on ILM's setup where they can just obtain high res fluid explosions and all manner of other templates - its all networked up and literally takes seconds for them to viz something - i feel sick haha!

guess i'm cranking up the settings and leaving it overnight lol!  here's a video - have a skip to 13.5 mins and check this out

how to make vfx artists green with envy by ILM

Once again massive thanks for your help Yon really appreciate you taking the time to jump on here and help me out so much

oh to add - i just cached out the low res pyro (well.. some of it!) as a .bgeo.sc and its working :D  i'm seeing the fine detail added on - thankyou :D

to give you an idea of what i need the cloud for here is a little teaser trailer i did for my anim i'm nearly done on! (wait till after the logo right near the end to get an idea of what i want to do!)
Iron man gamma protocol teaser02 - 2K

 

Edited August 29, 2016 by anthonymcgrath