Re: Ifu - cloud simulator and renderer back
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(L) [2014/10/20] [ost
by citadel] [Re: Ifu - cloud simulator and renderer] Wayback!If it's multiple scattering dominant, the phase function should not matter that much,
and would allow using reduced parameters, according to Jensen'02, the fast BSSRDF paper.
I think the key is in its genuinely high albedo, which is particularly difficult for path
tracing to fully capture.
(L) [2014/10/21] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!If real clouds scatter mostly forward but renderings of this don't come out right, it may not be the real-world physics that need redefining, for sure. But on the other hand, whatever makes the rendering look right.
With clouds, though, a good phase function won't help if the droplets aren't arranged in a realistic way, and this is where you'll really step into a pile.
(L) [2014/10/21] [ost
by citadel] [Re: Ifu - cloud simulator and renderer] Wayback!I agree not to redefine the physics, but using reduced parameters is more of a mathematical treatment. After all, we are just doing integration of the light transport equation.
The albedo issue is quite orthogonal to that. A close to 1 albedo either introduces serious bias for a finite-depth tracing method, or requires serious effort to address properly. I recall you using a scattering probability for the photons, which I believe is the albedo. For the correct physics, your photons should never stop scattering until they exit the medium.
(L) [2014/10/21] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!Clouds aren't much of a medium, though - quite possible for a ray to pass 'through' without hitting anything.
Rays in Ifu have a maximum depth of about 10000, but while inside a cloud mesh, they'll keep going until they find a way out.
(L) [2014/10/22] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!Looks more like clouds now, though I'd still say you're being shy with the forward scattering. What I've tended to notice looking at photos of cumulus clouds is that even though they look solid when far away, they get misty when you move closer.
I've two observations of the data from Ifu. First, since the clouds have no flat bottoms, they're already dissipating - I'm guessing most people associate cumulus clouds with flat bases, i.e., at the stage where they're still growing. Second, the output looks like it's from the mixing phase of the simulation, and if so, I'd recommend to either wait until the normal phase or to customize the heatmaps. And look for the beta 2 version of Ifu, should be out next weekend or so, for a bunch of improvements to the simulator.
(L) [2014/10/22] [ost
by citadel] [Re: Ifu - cloud simulator and renderer] Wayback!What's the exact setting for your moisture/dust scattering type? Is that related to the sigmas?
My further tests show that the simulation never converges to beautiful results, and tends to dissipate completely. Early stage seems more like it.
(L) [2014/10/22] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!I'd guess the reason the mixing phase makes more satisfying clouds is that the heat multiplier is larger for that phase. See Settings -> Simulator and the last two options there. You can increase the multiplier for stronger cloud formation, etc.
Changes to the mixing process were made for beta 2, and that version disables mixing by default, since it still needs more work. The problem with making clouds without first mixing up the atmosphere somehow is a potential loss in realism (eg, Entrainment and Detrainment in Numerically Simulated Cumulus Congestus Clouds. Part I: General Results by Carpenter & Droegemeier).
The moisture and dust scattering is for the atmosphere only; rays will scatter every now and then on their own. Moisture uses the same phase function as the clouds, and for dust I think it's just more or less uniform in all directions.
(L) [2014/10/27] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!The beta 2 version of Ifu is out. Comes with a bunch of changes, improvements, and new features (support for wind, variable terrain, HDR environment maps...). Work in progress, etc.
Get it here: [LINK http://personal.inet.fi/muoti/eimuoti/ifu/] (Linux/Windows 64-bit)
See the changelog and release notes: [LINK http://personal.inet.fi/muoti/eimuoti/ifu/ifu-changelog.txt]
For best results, I'd recommend exploring the various options in the program, especially the atmospheric ones.
I've updated the first post accordingly.
(L) [2014/10/31] [ost
by snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!Couple short video tutorials up:
[LINK http://www.youtube.com/watch?v=5B3CRZNemVM Ifu Silent Basics - Render Setup - YouTube]
[LINK http://www.youtube.com/watch?v=pWdLL1UNym4 Ifu Silent Basics - Atmospheric Settings - YouTube]
Bring your own soundtrack, etc.
More tutorials may or may not go up on the playlist later.
(L) [2014/10/31] [tby zsolnai] [Re: Ifu - cloud simulator and renderer] Wayback!Beautiful demo, congratulations! [SMILEY :)]
(L) [2014/11/02] [tby snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!Thanks, appreciated.
I've twice noticed in this thread people referring to Ifu as a demo of sorts; I wonder the cause? Personally, I see it as a 'tool', having been more of a concept and then a demo two years ago. Granted, the target audience is more along the lines of cloud enthusiasts than, say, production rendering.
(L) [2014/11/04] [tby snwy_] [Re: Ifu - cloud simulator and renderer] Wayback!Some more silent tutorials up:
[LINK http://www.youtube.com/watch?v=aXJQVe31-po Ifu Silent Basics - Creating a Pileus Cloud - YouTube]
[LINK http://www.youtube.com/watch?v=QRg9Z-LzbZs Ifu Silent Basics - Simulator Settings - YouTube]
[LINK http://www.youtube.com/watch?v=otI4VyC27yQ Ifu Silent Basics - The 'Cloud Blur' Option - YouTube]
Roughly in order of involvement, the first video being about simulating a specific cloud phenomenon, the last one about literal basics of Ifu usage.
(The video quality is basically limited to 480p - the best my monitor can do.)
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