Experiments with Volumetric Rendering

[rohandalvi]

Hello Everyone,

A couple of renders done using Houdini and Octane. Rendered using a single GTX 1080. The render time is relatively high but I love the look. The nebula render has very little post production. The cloud render was tweaked a little in photoshop using Color Efex pro.  These are part of a new training series on volumetric rendering.

Nebula - Render time - 1 hr 50 min at 4K resolution

 

Clouds - Render time 45 min for Full HD

 

Edited September 25, 2016 by rohandalvi

[goafreak]

Awesome renders! Looking forward to the tutorials!

did you compare the render times with redshift?

[rohandalvi]

Redshift is about 2-3 times faster but getting the look from redshift turned out to be surprisingly a lot more difficult than I had thought.

There were also some issues with some of the builds where Volumes weren't rendering. Octane is slower but I get the look fairly easily and since these are mostly stills I just let them render out. Like the nebula render is pretty much in camera including the glow and glare on the stars. I just did some minor color balance stuff in Photoshop.

I'm still figuring out the redshift volume shader, once I'm happy with the look I'll post some redshift renders.  But for now it's Octane

[goafreak]

Thanks for the answer. A few weeks ago I tried to replicate this kind of effect:

Mantra was super slow, so I did dome experiments with redshift. It is definitely faster than Mantra, but I just couldn't get the same look as the video. Would be interesting to see something similar with Octane   

 

How would you approach this effect? I tried several ways, with mesh lights, incandescent materials, point light instancing, but I couldn't get a similar result. 

Edited September 25, 2016 by goafreak

[rohandalvi]

This is a really rough test with Octane. I only have the Mesh streaks lighting up the cloud and since that has more polygons they tend to cause a lot of noise so I need simpler lights. But this is about 20 mins of work without trying to optimize anything. This is rendering it pure brute force path tracing with 3 light bounces which affect the volumes as well but I think I can figure out a way to cheat it. I can turn the light streaks into volumes and add it to the cloud structure as a temperature volume. The you light up the whole thing like you would light up a Pyro sim using a pyro shader. 

The thing with Octane is that achieving the look is fairly easy. You just need to manage to the rendertime. That's the tricky part.

 

[rohandalvi]

Alright, so I managed to get it faster and cleaner with lesser samples but using a purely volumetric approach. The light streaks inside are also volumes.

The previous render was 5000 samples and it took 10 mins for 1100 pixels and it was still very noisy.  This is a Full HD render. It came down to 6 mins for 1500 samples and it's a lot cleaner.

[goafreak]

Hey Rohan,

awesome renders, I really need to test Octane  

The pure volumetric approach is very clever, didn't think about that when I was doing my experiments. My goal was to get the look of the light particles traveling through the volume, but heating the volume with the particles could work also, have to test that. 6 minutes rendertime are much better, the best I could get was around 30 minutes with still very noticeable noise...

 

Cheers,

Chris

[ikoon]

Hello, thank you very much for trying to develop new techiques and sharing with us. I am also going soon to buy decent GPU + Redshift, hopefully in few months. For now, I did few experiments here and skilled guys contributed. Maybe with Redshift and some biased fakes we could make it nice and fast?