GI Blotches on Interior walls

[Streetwise]

I'm having an issue with blotches on an interior wall. The material is just a diffuse color, .7 Reflection, subdivs 96. Nothing special. The lighting is HDRI light dome.

All of my lighting and reflection passes look to be super clean. It's the GI pass that is producing horrible results (see attached).

IR/LC
Subdivs 1,12
IR -4,-1 HSph.100, Interp. 20
LC secondary multiplier .88
LC Subdivs 1000, .01sample

[glorybound]

Are you using Interpolation for your VrayMtl? I have had strange things happen when it is enabled.

[Streetwise]

Interpolation is "off" for that material. BUT, I just turned off the "Use irradiance map" Option and a small sample of that area looks good! Since it's a flat wall, I'm not sure if turning off that option will mess with other things or not.

[MoonDoggie]

Turning it off will force anything with that material to be brute forced. In this particular scene it might be alright, but I don't suggest turning it off.

Turn back on Use Irradiance Map.


Try the following:
1. Replace the wall geometry with a plane/Box, apply the same material, re-render (Eliminates the idea the problem is with the geo)
2. Apply a default VRay Material (gray) to the wall, re-render (eliminates material problem)
3. if both of those don't produce a good result, your problem is likely your render settings, move to step 4
4. Try not using any LC and doing a test, the render will be darker and different, but you can still check for those types of artifacts
5. If it's still doing it, reset your vray by changing the renderer to Scanline and back again, setup IMAP/LC with defaults and re-render
6. Should be fixed by now, retune your settings (cross fingers)

[tashko.zashev]

Hi,

The steps suggested by Colin should be enough to localize the problem. But if you still can't find a way to get a render result without splotches, please send us your scene file to support@chaosgroup.com for further investigation.

[tricky]

Minimize the minimum IRmap map settings. We typically use -10 as a minimum and -1 as a maximum for large, flat surfaces (most architectural shots)

[vlado]

This might also be due to overlapping surfaces.

Best regards,
Vlado

[Deflaminis]

I'm a big fan of selecting the offending geo, going to Vray Properties, and increasing the GI subdivs for that object only. Seems to work pretty well for me in lots of cases. Slatwall for example never seems to get the right amount of samples compared to everything else.