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Fire Shading

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Jean-Luc Gason
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Hi,

Can someone point me to a good fire shading tutorial. I looked at the Pyro video's on SideFX.com but my main problem is that I'm trying to render fire like a god fireplace and all my fires lack transparency.
They are too opaque, too massive, and I don't seem to find the parameter I should play with to change that…

Of course being total beginner, I try to play with the built-in Flame shader, maybe it's the shader that is too basic to allow the renders I look for…
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anon_user_37409885
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for fire transparency try modifying the ramp when you set the ‘Density Model’ to ‘Fire Density As Actual Density (Pyro1)’ in shop/flames/shading/ when using the flames shelf tool

these Pyro2 videos might help:
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=25248 [sidefx.com]

Attachments:
Screen Shot 2013-05-31 at 7.04.23 AM.png (39.3 KB)

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anon_user_37409885
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for flame size, try a smaller ‘Division Size’ setting in obj/AutoDopNetwork/pyro

the attached pic; the left is the default ‘flames’ shelf tool , the right is setting the ‘division size’ to 0.05

Attachments:
Screen Shot 2013-05-31 at 7.38.43 AM.png (137.0 KB)

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Jean-Luc Gason
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Thanks, that helps a lot already.

I tend to see some “grid” or square cell in my rendered fire, even with volume set to 1 in mantra, is there another param i can tweak to get rid of that ?
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old_school
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That would most likely be the Volume Filter set to Box with a filter width of 1 on your object.

If you change this to Gaussian with a width of 1.2 should get rid of the artefacts but introduce some softness. Try reducing the filter width or use a sharper filter such as Catmull-Rom.
There's at least one school like the old school!
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Jean-Luc Gason
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Thanks Jeff
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Jean-Luc Gason
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Tried to play with the filter, set it to Gaussian, still the same problem, I'll do and attach a crop/zoom of the problem, so you can see it…
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Jean-Luc Gason
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Here is an exemple of the problem I encounter

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Test051.jpg (56.0 KB)

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anon_user_37409885
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you need more voxels/detail in there. Try the Upres Container shelf tool in the ‘container tools’ shelf
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Jean-Luc Gason
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Ok, So I use the UpRes Container tools, and get a second DOP node in my OBJ root, called UpRes, but I cant see any difference when rendering, and the upres node in the DOP network don't seem to have simple “more quality” setting…

Any video or docs I can read to understand the upres workflow in houdini 12, all i could find was for houdini 10 and it seems this workflow changed since then…
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anon_user_37409885
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I don't know of any really simple tutorial that takes it step by step, there probably are some but I don't know them. I've attached a scene and a screen-grab showing upres - the right-side one is an upres of the left explosion.

I personally think it's probably best to try to get a more fundamental understanding of the whole fluid system. i.e. the ‘make more detail’ option of Upres is in there in the ‘smoke object’'uprespyro' node -> division size. Once you know that the fluid system works on a grid-like box full of voxels, or volume pixels, then you know that the detail is only as good as the amount of pixels plus the interpolation between them. Below are some excellent tutorials.

PQs tutorials are invaluable
https://sites.google.com/site/pqhoudinitutorial/home/videos-on-dynamics [sites.google.com]

Especially Smoke / Pyro in H12
http://vimeo.com/38287079 [vimeo.com]

http://vimeo.com/44619541 [vimeo.com]

Then the masterclass gives you the inner workings, which builds the foundations
http://lesterbanks.com/2012/05/masterclass-in-building-fluid-solvers-from-scratch-in-houdini/ [lesterbanks.com]

Attachments:
Upres.png (96.4 KB)
Upres.hipnc (1.6 MB)

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