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SickleYield — [Tutorial] Creating Dust And Atmosphere in Iray
Published: 2015-03-24 17:01:52 +0000 UTC; Views: 133154; Favourites: 381; Downloads: 0
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Description
A video version is here.I learned this method from jag11 on the DAZ3D forums , who is thanked for permission to use it in this tutorial!
In 3Delight there's no way to create atmosphere or godrays (the rays that are visible when light passes through dust or particles). There are products to facilitate (one of them mine ), but most are either not the easiest to use or ultimately just a faking of a feature the engine lacks. Many artists use postwork instead.
DAZ Studio 4.8 Beta's new Iray engine also lacks a native mechanism for creating atmospheric volumes - but it can be easily convinced to produce them! They will come from your lights and react to objects in your scene. I did a test image of Jack Tomalin's Chapter House Iray scene (free to Plat Club members ).
The method is:
1. Load your scene into DAZ Studio 4.8 Beta.
2. Set the Environment to Sun and Sky in your Render Settings.
3. Jag11 says to set time of day to 12 noon. I set it to 3 p.m. in the above test. I think what matters is that you set the SSS direction properly for the light direction (below).
4. Make sure that your camera headlamp is set to OFF. This is in the camera's parameter settings; you must render through a "real" camera and not the perspective, top, right, etc. views.
5. Create --primitive--cube. Other shapes will probably work. The important thing is that you scale it up large enough that your camera cannot see past its outer edges, ideally as big as your room (or if outdoors, really, really huge). The camera must be outside the primitive.
6. Select the cube in Scene Tab and look at its surface in Surfaces tab. Select the surface. Apply the Uber Iray Base shader. Turn OFF all the glossy settings (glossiness, glossy layered weight, etc.)
7. Scroll down to the Refraction. Set the amount to maximum and the index number to 1.00 (I believe it's 1.5 by default).
8. Scroll down to the Thin Walled setting. Set it to OFF.
9. Scroll down to the SSS settings. Jag11's recommended settings are
Scattering Measurement Distance: 50
SSS Amount: .03
SSS Direction: 0.5
For the huge room in Jack's Chapter House scene, I used:
Transmitted Measurement Distance: 100 (same as the Scattering, leaving it at 0.1 produces black renders)
Scattering Measurement Distance: 100 (I reasoned that the rays needed to go further into the room)
SSS Amount: .05
SSS Direction: -0.45 (which, as it turns out, was wrong; in the version shown I've corrected it to 0.5.)
Adding a higher SSS amount will make your atmosphere more dusty. I used an incorrect value of SSS direction at first. According to DAZ's docs, "Negative numbers (-) backscatter to the direction of the light source. Positive numbers (+) forward scatter away from the direction of the light."
Here's a scene you can use to test this, and a copy of the most successful version of the shader I used.
So really, you should always use a positive number of SSS direction for this. This is probably why I didn't get very defined rays in my scene until the second try (the version you see for the Chapter House scene now).
In the second scene, the Park Side High Lobby, I used an HDR for fill and spotlights for lighting; there is no "Sun" light. So that is definitely not mandatory as a lighting method to get these rays.
I look forward to your renders using this method!
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Hey, thanks. You have been so helpful with your tutorials.
When I use these godray cubes as you've recommended they work great except I'm at a loss at how to deal with what I think is a lensing effect (like a telescope or eye classes).
I have two situations.
a) Outside the window of a room I'm trying to make godrays in is a real 3D model, eg Merlin's The Church is seen out the window, but when I make the godray cube the church models shifts way to the left and shifts much close to the window than it really is. I have to manually adjust it's position multiple times, do a render, adjust again, because I can't tell have far the the shift is until I render.
That situation is at least manageable but the next I don't know what to do.
b) I have a nice 2D background of Manhattan from on an image search on one of the search engines. I set it as the Environment background & visible in render. I position the set so that the camera gets a good view out the window of the NYC skyline. Without god rays it looks great but when I do the godrays the NYC background on the other side of the window (uses a UberIRay glass shader) disappears and all that is scene is like when you do Sun-Sky with no 3D set so that the sky is white and at the bottom below the horizon line the ground is grey.
How to I remedy such a problem?
Thanks.
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Hallo hallo! What are the refraction settings on the godray cube?
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Hey thanks.
The Godrays Cube
a) All the glossy is turned off.
b) Refraction Index =1.00 / Refraction Weight = 1.00
c) Transmitted Measurement Distance = 5.0
d) Scattering Measurement Distance = 5.00
e) SSS Amount = 0.0050
f) SSS Direction = 0.33
g) SSS Node = Mono / Thin Walled = off
I should note that I can make the room super dusty or relatively dust free by adjusting TMD & SMD or the SSS Amount. There is a lot of leeway in adjusting those before the effect busts. So that part of your tutorial is fine. It's just this unintended effect.
Also the set I'm using is the Window Seat ( www.daz3d.com/window-seat) and I should not that if I use the original glass shader material applied to the window glass that in some iRay renders it causes the backdrop to disappear too. So that problem is not unique to these Godrays cubes. That's why I replaced the glass shader material supplied with that set with the DAZ UberIRay glass shader material, which doesn't have that problem (when no Godray cubs are in use).
For the glass on the window the refraction index is 1.55 and the Refraction Weight is 1.00. The glossiness settings are left on for glass reflections. Thin Walled is On so those over Godray cube values aren't relevant.
Maybe I should lower the cutout opacity on the window glass to 0.0? That will rid any reflection in the window though.
Maybe I need to make a skydome for the whole scene instead that can be modified to cause godrays?
Oh, I can also make the Window Seat invisible during the render and see if a lensing effect has simple shifted the background way out of sight of the window's view.
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Well OK,
a) I hid the Window Alcove and rendered and the NYC background was nowhere to be found.
b) I showed the Window Alcove again but set the cutout opacity of the glass on the window to zero and still the NYC background disappeared.
So I can try making a skydome that will make godrays but I also think that won't work.
I think a workaround that should work is if I create a DAZ primitive plane the same dimensions as the NYC background and make the background the texture for that plane. Then I position the plane in the window were I need it. I think I will possibly need to turn on the emissive surface for that plane though.
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Well the backdrop on a DAZ primitive plan does work. The lenses effect magnified to be about 33% closer to the camera. I also had to turn the emissive surface on (default values I left alone then) to make the plane look like it was 3D geometry lit by ambient light rather than a picture on a 2D plane in a 3D scene.
The plane I created 1mx1m and then scale to 4928 x-axis, 3264 z-axis, 0.01 y-axis because that was the pixel resolution of the original background image. Because of the 33% magnification of the image I doubled the scale on the x & z axises and double the z distance to the camera.
Thanks so much! I will mess with volumetrics in scene encompassing skydomes and godrays in those after I finish these renders!
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I'm glad you found something that works for you already!
Refraction is literally light being bent as it passes through something. As a result, even using refraction at 1.0 (a very "low" value) can still result in images being displaced from a given point of view. You can turn refraction down or off completely and just use cutout and transmitted distance/scattering distance to determine thickness of the fog, just be aware that the fog defaults to really very thick without refraction on.
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OK, thanks. That is interesting to learn. I've been wanting to try making fog like in the early morning hours.
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I have to fav this so badly.
And downloaded...
... just watched. Hey, hey hey, SY using Karen's Replicator too. Such a great little tool. It saved my bottom so many times.
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Thanks a lot for the guide which was very helpful!
I tried it with one of my very first picture .. I am a newbie with 3d.
www.renderosity.com/mod/galler…
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Nice job! Looks like it worked!
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After fighting for some years with godrays and volumetrics, finally i have found the Grail!
Thank you, your video is also extremely helpful. 
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You're very welcome!
I tend to fake them with transmaps myself most of the time because it's faster, but if you want "real" in-engine volumetrics, it at least is possible!
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I have tried pre made volumetric cameras as well, and aside for losing my sanity i haven't obtained the same result as i did following your tutorial.
I have also your easy Godrays, but my experiments with Iray ( my fault) haven't worked well yet...i may try to apply the same criteria ( of the video) on those surfaces though.
Since i am no expert on mapping, i am afraid, lol.
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With the transmapped godrays you don't use the volumetrics at all, you turn down the opacity a bit and add emission (if you're talking about the pre-Iray one; we did do an Iray version later). In this image I used Expanded Godrays Iray out of the box (again, I may have turned down opacity even a little more).
Mature Content
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Terrific.
I have wishlisted it, for now i have to stick with the complicated rays, but the positive side is that i am learning something new.
Thank you once again for your super useful tips and tutorials, changing engine is offering quite a challenge, lol.
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I also have a free version for 3Delight, but it should be easy to use in Iray too:
www.sharecg.com/v/72345/galler…
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Yep, already used them and discovered that they works well even when not converted for Iray. 
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After watching your video, I finally was able to produce God-rays. I never could so it just folowing the text. I had to do some post-work to get it to look the way I wanted, but I finally got it.
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Great, I'm glad it helped.
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I’m doing another render to see if I can get the effect from Terra Dome 3 atmosphere. I’ll tag you when I upload the final results. Thank you for the video.
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Terra Dome? Ouch, that's gonna be a long render with that much SSS. Good luck!
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Most of my renders are long.
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TD3 did produce rays but it wasn’t the same. Your method produced a lot of littles ones were as TD3 had more like 2 or 3 big one. I’m going to try 1 ore render with your method.
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I really like this better than Atmocam for some reason - it just seems to clear up and interact with light better. I put it in one pre-made scene and the difference was outstanding; I tried another pre-made scene of mine which was also a simple portrait, and while it certainly added volumetrics/fog to the scene, I couldn't get the light-beam effect I was looking for. There was nothing 'narrow' to enclose the light through mind you, so I tried using point lights from IG's light set - any advice on getting Godrays?
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I thought I was the only one having issues with Atmocam, think I will have to try this and see how it turns out, thank you for the tip SickleYield
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It's harder without an aperture. I guess you could try setting a spotlight as that? It's not called aperture but there is an option in the spotlight settings to change to a door/window shaped thing.
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Thanks! Just completed my first experiment with this technique (using a spotlight rather than sun/sky).
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You're very welcome! It came out nice.
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And making SSS direction negative does indeed allow for backscattering....
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Can this work for say, searchlights at night? I'm trying to do a test render for a scene for a Godzilla fancomic that is a night scene with searchlights on him, and have been fighting with trying to get a good result for over three days. I either get no searchlight beam on him at all or the scene looks like the sun is twenty feet away from Godzilla. The Iray Godrays props just won't work, and I've tried spotlights with iray settings applied, primitves with Iray Real Lighting shaders applied, and the IR skydome sun set up like a spotlight, and everything is either no light on Godzilla or sunblasted. The environment itself is not an issue, weirdly. It's just Godzilla. Always looks like a pitch black shape stuck in the center of the scene.
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It should. At least it costs nothing to try it this way.
Remember that the larger your volume, the higher the transmissive distance needs to be so you don't get murk. If your fog looks too thick that's the issue (I say this because I assume if you're putting searchlights on Godzilla you're looking at an extremely large volume). The settings I suggested here are way too short/low for a huge scene. You might need to have transmissive distance 1000 or something even.
It's going to be slow to render. High transmissivity in a huge volume always is.
If Godzilla keeps coming out black you may also need to double check his shaders' Iray settings (is glossy set to 0%? Some things convert that way and it's never good for lighting things properly).
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I played with the settings for the skin, but I dunno if it'll work, as the models frankensteined together (Valandar's Kaiju and Scott Ayers GFW Godzy) are for 3dlight. I tried the human surface shader but it screwed everything up, so I tried just the Uber Iray surface.
The slow render times might be an issue, as it's gonna be for a fancomic, and I will need to get at least a couple panels a day, preferably more.
Right now I'm trying a cone with the Godrays and Real Lighting settings and shaders applied; maybe that will work. If not, I will try this technique. Also in a DAZ forum thread I started about this, people have given me other ideas to try. So at least there's SOME options at this point! Thank you!
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You have a pure golden heart to help,and share,Thank you so much
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And the weirdest thing now ... I can finally see all the options you listed.
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Well, I'm glad they did show up in the end.
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I did double check the engine is set to Iray. Once again, I have SSS options for a primitive Cube and refraction along with refraction index and thin wall option. And again ... no time of day option.
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3. No option under render options to sun and sky
8. Last night after I commented I had SSS options for a primitive Cube and refraction along with refraction index and thin wall option. Not today tho, attempted on cube and plane.
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Can you double-check that your render engine is still set to Iray and not 3Delight?
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