Hello,
I’ve been working on this stair for work, that we built years ago but can’t get any photos.
Top right, the glazing bars are black.
Replaced the object, which made no difference.
Vray 1.46.15 and viz 2005
Irr + Lc
Have tried rendering at 3000ish pixels high with high render settings
tried photon map for secondary.
Don’t think it’s a lighting problem!
Any ideas?
Geoff
Hey Geoff ..
are the Bars behind the glass ? .. if so try increasing your global depth.
Maybe their normals are flipped?
Best regards,
Vlado
Bars are in front of the glass.
All of the glazing bars are instances, so the normals should all be one way or the other?
I’m rendering a big one again so I’ll post a blow up tomorrow
Geoff
could it be the reflection cutoff?
or maybe the glass is coplanar with that edge?
If they’re instances and you mirrored them, you can get inverted normals. Looking at the image it seems like it could also be coplanar faces
Hey Vlado … like your Avatar … a little hint there hey ??
My money is on Dynedain… flipped normals.
If you are relying on 2-sided materials - make sure “reflect on backside” is checked.
There was a nasty little bug with Mirrored Instance’s where it turned objects Black … but that was rectified..
Try to play a bit with the SRB … maybe it solves it
Here’s a blow up of that area
THink I found the problem. 2 sets of glazing bars. co-planar faces
DOH! 
Odd that it’s only done it that area when the whole lot of verticals were duplicated
Can’t seem to a region or crop render all of a sudden. Why is that?
Tishchaos what is SRB?
…
Just rendered left to right reversed. Co-planer faces. So who won the bet?
Thanks for all your quick and insightful replies
Geoff
Geoff, SRB is Secondary Raytrace Bias and is located in the Global Switches rollout - if you increase it to 0.001 it can solve the problems with co-planar faces. But the best solution of course is to just delete them. 
It’s not black anymore…it’s grey!
The horizontal bars are the same material and are OK.
I’ll keep looking into it…
Did you try SRB? What happens if you hide everything except the problematic objects? You can send me an email with a stripped-down scene if you like.
Tishchoas, I haven’t tried srb. Will give it a go.
I’ll send you the scene as well
I’ve just noticed some black puffiness at the top
How do I get rid of it?
I’m not great at understanding all the setting.
I just use flipside’s tips
settings are, for a 2480x3507 image
Primary : Irradiance
min/max=-5,-2
Clr tresh: 0.35
Nrm=0.4
Dist=0.3
Hsph= 50
interp samples=20
Seem to work on most scenes
Secondary : Light cache
Subdiv: 1000
Interp samples 10
Left on defaults really
I don’t think that min/max rate of -5/-2 is very appropriate because it is very low for an image like this - try -3/-1. And your Normal Thresh should be between 0.1 and 0.2, not 0.4 - this might be the cause of these! Try Nrm 0.15.
The lightcache is ok.
If those don’t work, send me an email.
I’ll adjust those settings and see what happens.
Thanks.
Have e-mailed scene in regards with grey vertical glazing bars.
I adjusted the scence settings for the black puffs and the grey bars are now white!
Don’t know if the black puffs have gone yet as I have lost all my DR buckets 
Thanks, will post finished image in image uploads tomorrow if I have time to render tonight.
The problem was in the irmap settings. Set it to High preset and also install the new build 1.47.02.
Larger size image:
