Volumetric Atmosphere Effects Iray

Szark

I wonder if we will ever see this in DS http://blog.irayrender.com/post/132864644411/volumetric-effects

SimonJM

As that is from 2 years ago and references stuff done by Sickleyield in DS, I'd hope so!

Szark

I did find a post on Nvidia Forums regarding this after I posted this date 2016 saying the same thing. Make a primative around the scene as use the MDL Wax SSS shader for the volume, adjust SSS parameters to suit. So it doesn't look like they have a built in system. 

BeeMKay

Here's the post... https://www.daz3d.com/forums/discussion/107421/fog-effect#latest

Szark

Thanks for others that need this Bee. 

liquidphantom

Szark said:

I did find a post on Nvidia Forums regarding this after I posted this date 2016 saying the same thing. Make a primative around the scene as use the MDL Wax SSS shader for the volume, adjust SSS parameters to suit. So it doesn't look like they have a built in system. 

Do you have a link for that?

Thanks

Szark

yep https://forum.nvidia-arc.com/showthread.php?15495-Volumetric-Fog from May 2016

Tobor

Pete is talking about a built-in feature of Iray, as opposed to a 100% materials definition approach. I've seen these posts, too, but whatever nVidia may have added to Iray for specific volumetrics outside of using just a shader (SSS stuff), it doesn't appear to have yet reached D|S. The blog post Pete mentions is quite cryptic without any follow up, suggesting that the full functionality isn't yet in a stable Iray release, or it is there, but not yet exposed in D|S. There are numerous Iray features that D|S doesn't support, such as motion blur.

Szark

motion blur, man how long did it take to get it for 3DL. Drool

thilion

I don't know since when it is possible to achieve this volumetric effect with the standard iray uber shader, but it is - if you know the proper settings. I don't remember the exact values by heart, but...

You start with a simple cube that surrounds/encases your scene and turn off the volume thin walls. Then it is the SSS amount you need to set right. The problem is that the default range goes from 0 to 100 and the standard notch is 1. But a working value is more like 0.0000001 (6 zeors after the point) to 0.000005 (5 zeros). Everything way higher results in a solid white mass. So, in order to make use of the slider, set the maximum to 0.000005 and the notch to 0.0000001. Then you can change the slider and see how the atmosphere gets thicker.

I'll post some example images next time I'm working on my render PC.

thilion

By trying to find this discussion thread I noticed that there are numerous postings about atmospheric volume (volumetric atmosphere?) using Iray. You just have to use the correct keywords when searching. Anyway, in case someone is looking for this and lands here (like me a few days ago) I'll post my experiences anyway.

I was wrong about the SSS Amount. It doesn't have to be 0.000001 if you set the value for Scattering Measurement Distance high enough. So here is what you need to do in order to get atmosphere in your renders:

1. create a simple cube
2. set its material to the standard Iray Uber Shader
3. leave most of the iray settings in the Surface Tab as they are except those in the screenshot with a white value (see attachments 1 + 2)
4. 
5. if you want just some god-ray effect, like light through a window, size and position the cube only in front of the window (see attachment 3 - I colored the atmosphere-cube only to show it)
6. 
7. otherwise extend the cube throughout your entire scene; it's going to be like a fog then

Here are two sample renders what it can look like. I placed the cube in front of the first "windows" and then in front of the other windows.

Play with that and also play a little with Scattering Measurement Distance and SSS Amount. You'll see the differences.