Started by Matt, June 13, 2018, 07:18:11 am
Quote from: ajcgi on June 20, 2018, 06:20:02 amFirst issue for me is that there's a scale difference between the grid and the camera of 1000, taking one unit in Houdini to be one metre.
Quote from: ajcgi on June 20, 2018, 09:36:40 amTo begin with I also got nothing. It took 3 of us here to figure it out at lunch. Ultimately, the density attribute in the vdb is still named 'Easy cloud 01' and not 'density' which Houdini is expecting.
QuoteI've now got the scene up to the point where the shadow works! The density on the pyro shader had to be reduced to 0.2 and then it was all go. More images attached. There's a slight offset in shadow position.
Quote from: paq on June 20, 2018, 09:32:05 amSo I have a first setup in place, done by hand has Clarisse don't load .FBX.Scaling is right (it's a 10Km large scene).
QuoteDirect light exposure is set on 1.5, and I have an env.light on -3 ()
QuoteWith the a default volume shader settings, and the overall density reduce to 50%, it looks more like smoke than cloud. I'll post the scene on Isotropix web site (may I Matt ?), because I'm really curious what kind of trick we could use to get a proper cloud look
Quote from: Matt on June 20, 2018, 06:59:13 pmNice! Strange that the density multiplier is a seemingly arbitrary value. There seem to be some other differences besides the slight offset in position. The denser parts of the cloud seem denser in your render. Is there a slightly lower density that makes the denser parts look closer to mine? Maybe 0.1?Matt
QuoteI've uploaded a new VDB to the same folder:vdb_calib_01/scenes/vdb_calib_01_export_v003.vdbThis is named 'density' instead of 'Easy cloud 01'.Does this solve the problem with visibility that some of you had with v001?
QuoteDirect Visibility and ShadowThe strange thing is that the Arnold volume shader has a transparency parameter which is set to 0.3679 (0-1 space). With this value, density has to be at 0.18. The shader doesn't accept more than 2 decimal places so who knows what exact value needs to be, but it looks like a good match. Disabling transparency will result in a black cloud and shadow, so I've left this value where it was.I thought it's meant to produce 0.5 in sRGB, but it seems to be an arbitrary value, if it's linear it should be 0,2176 to produce 0.5 in sRGB, if it's in 2.2 gamma it should be 0.7297 to produce 0.5 in linear space - no clue what the reasoning is behind this as a standard value.Scattering/GIThis is where transparency controls everything again. If I want the cloud to look good I need to increase the value but then the shadow will be a lot lighter than in TG's example. The GI result further down is what comes out when rendered with the same shader that matches the diffuse/shadow render.I guess it all comes down to how volumetrics work in Arnold, there's no simple way to achieve the same results for diffuse/shadow and GI.General light intensity has to be around 1.68 to produce a close match to TG's exposure/brightness.
Quote from: sboerner on June 21, 2018, 11:38:45 amI'm curious why my Density setting for the Arnold volume shader has to be so much smaller to produce the same result (0.003 vs. your 1.68). Setting it to 1.68 here gives me a solid black cloud. I've matched your transparency setting (0.368 on my system) and that works fine. Tonight I'll mess around with the Scatter and Transparent settings to see if I can get some natural looking clouds. (So far I've left Scatter Weight at 0 to replicate the black cloud and shadow.)I'm using Arnold Core 220.127.116.11, not sure if that makes a difference.
Quote from: sboerner on June 21, 2018, 11:54:44 amThe VDB and grid both came in at 100m on import, so I had to scale them to 10km. I'll remove the scaling to see what difference that might make. Good thought, thanks.My understanding is that there were some significant changes between Arnold 4 and 5. Many of the shaders were also updated. So maybe that's making a difference, too.
Quote from: pokoy on June 21, 2018, 10:08:38 amAlso, after playing with the VDB trying to get a decent cloud look, I have to say that TG renders clouds way better than anything I've seen from Arnold and Corona so far. Way more realistic and surprisingly not much slower, even faster with higher GI bounces. Well done