black staining under ledges in Vray

[Paul Welch]

Hi can anybody help me. When I try to render these sorts of scenes with lots of cornices and ledges i get this black staining. Primary is irradiance map secondary brute force vray sun and physical camera although even if I use a direct light or vray light I always get this staining. I have rendered with really high irradiance map settings and checked the model for overlapping surfaces and I am sure it is fine

 

Any help much appreciated[ATTACH=CONFIG]37262[/ATTACH]

[alywhosane]

I guess this is a problem of modelling i think ur having a problem of edge smoothing...the last time i had a problem of the same type i converted to editable poly n offcourse made sharp edges n corners so that i can apply a TurboSmooth ..that really helped and i got over the problem..try doing the same..it mite help

[Jason Matthews]

Could be an anti-aliasing thing. Post your settings.

[Paul Welch]

Im using Catmull Rom and ive tried Mitchell Netravali I know these are the edge enhancement filters here are the settings Jason your help woud be much appreciated.

Thanks Paul[ATTACH=CONFIG]37298[/ATTACH]

[Paul Welch]

hi Jason I have posted the settings

your help would be much appreciated

Thanks

Paul

[Paul Welch]

sorry those settings were for an older file using light cache as secondary. These are the actual settings. Just got in the office, just waking up.

[ATTACH=CONFIG]37299[/ATTACH]

[Jason Matthews]

Funny. The only settings you didn't post is your image sampler. Change the image sampler to Adaptive DMC. In the Adaptive DMC dialog box uncheck "Use DMC sampler thresh." box. Now change your Min subdivs to 2 or 3 and the Max subdivisions to 5 or 6. Change the Clr thresh. to 0.005 or so. Now go back to the IR map and change the preset to medium. Reduce the HSph. subdivs. to 20 or 30. Then go to your DMC sampler and change the Min samples back to 8 and the Noise threshold back to 0.01. This should smooth out everything.

 

If it DOES work, then go back and reduce the Clr thresh. a little so it speeds up your rendering.

 

If it DOES NOT fix the issue, maybe try increasing the Max subdivis. The Clr thresh. should not have to be set too much higher than .005 for exteriors.

 

Hopefully this works for you. Every scene is different.

[Nic H]

looks like bad modeling - as it only happens noticeably on those cornices that i assume are lofts or sweeps?

try it with BF/BF to see.

 

its nothing to do with AA

 

could be completely wrong though!

 

btw you have some insanely high DMC sampler settings 16 min, 4 x global subdiv, 0.002 etc.

i find adaptive DMC much better than Adaptive Sub as far as antialiasing goes.

[Paul Welch]

It is not my scene and not my model it is somone elses model and is a few years old, itis construcetd from an editable mesh in three pieces. I ran an STL check and there are numerour errors multiple edges etc but no overlapping faces. I constructed some other models and these rendered fine. I had put the high settings to try and see if that would work I normally have DMC at 8 global at one but leave 0.005

 

Adaptive DMC does work better and Jasons advice definitely smoothed some of it out tweaking the colour threshold. I tried it on another model and it worked great so thanks for your help everyone.

 

By the way Nic what do you mean by BF/BF?

[Jason Matthews]

Obviously if it is not modeled well there are no settings in the world that can make the geometry fix itself.