Help on optimizing GI for interior scenes.

[tarjepladsen]

Hi!
This is my first real project where I'm doing interior renders.
And I'm really getting close to the finish line, but I need some help on optimizing the Global Illumination settings for my scene.

I'm using Irradience map and Light Cache and even with really high settings I still get splotches on the "white" walls. I really would like to get some input on how to smooth out those spots and still keep sharp shadows and precise GI everywhere else. Any help would be appreciated!



Hi-res: http://dl.dropbox.com/u/4604241/cam_...401_A_v004.jpg

[Boris Horosavin]

Hi Tarjep,
I will try to help you but bare in mind that I'm still on older version of Vray, therefore options and interface I use are a bit different. Anyway, here are several tips:
1. I suppose you have Vray light planes outside the windows casting light. Sometimes splotches can occur when light rays hit through windows glass material. You can try removing glass surfaces to see if that is what makes the problem. You don't necessarily need to erase those surfaces; you can choose those objects, open options menu with right mouse button, select Object Properties and uncheck Cast Shadows/Receive Shadows boxes.
2. Observe if there is some other large transparent or translucent object that might interfere with lighting, blocking light source and repeat the procedure.
3. I'm telling you this because your Irradiance map properties are, in my opinion, way too high for a scene like this. It takes too much time and resources needlessly. You should easily go with subdivision 40 (I usually use even less). Too high settings can sometimes make objects look artificial and unnatural, for my taste at least. However you could try tweaking your Noise threshold (Adaptive DMC settings), lowering it down to 0,003 even 0,002. That should probably remove most of the noise you have.

[tarjepladsen]

Hi thanks for your reply!

I know my Settings are quite high, that's why I don't get why there's still spots on the white wall...
Suppose I could increase the Interpolate samples for the Irradiance map but that might make the GI more washed out in other areas...

I've got a dome light that supplies most of the light for the scene. I also have some area lights on the outside of the windows that are set up as Skylight Portals, and I've checked Store With Irradience Map since it's supposed to decrease render time.... but idk if that makes it more noisy.

I'm pretty sure it's not the Noise Threshold since this is more like artifacts than noise...

[Boris Horosavin]

Hi,
just for the sake of my curiosity, please, try decreasing the noise threshold, down to, let's say 0,002. you can peacefully lover irr. map subdivision (hell, you can even lower light cache samples)
as for lighting, you should know what suits you best, but from my experience the easiest solution is often the best. if you have time and will try like this: remove all the global lighting except environment , for which you can choose white or some light-blue color. outside the windows (20-50cm outside) put vray lights in shape of planes, roughly the same size as the windows and tune their light amplitude and color.
this is the most common setting and you should have the least problems with it for interior (and believe me I tried all kinds of stuff)

[tarjepladsen]

Hey I really appreciate you taking time to anwear this!

To make it easier to tweak the GI I gave it all the geometry a white color, and Tweaked it from there. Also turning off the Store with Irradiance map helped a whole lot. But after I tweaked the GI and returned to the textured scene it became a bit "splotchy" again. So I turned Gi up quite a bit and let it render overnight. Took way to long, but at least it looked ok...

Think I have to get a bit more familiar with how all the settings affect the scene. Right now I feel that I'm walking in the dark

This looks like a good place to start...
http://renderstuff.com/irradiance-ma...s-cg-tutorial/

[tarjepladsen]

I'll try your tips using the Area lights outside the window the next time I'm doing a interior project.