Vray Sun with Vray matte properties

[bencowell]

Hello,

We're using Vray Physical Camera along with Vray Sun in Linear colour space. Our usual work-flow is to separate characters from backgrounds in passes, otherwise our render times go through the roof.

This is our first production using the Sun and the Physical Camera and so we're a bit confused with strange behaviour. When setting the background to be a vray matte object I'd expect to see my character appear looking exactly the same as a full render only without a background. However they're appearing much brighter.

See the attached image.



Any help would be greatly appreciated.

All the best,
ben

[Dariusz Makowski (Dadal)]

Why wont u just select all object (ctrl + a) right clieck, and uncheck Visible to camera?

[bencowell]

Hello,

I could do this, but then I don't get my character matted out by the fg objects. I can deal with this of course .. but I'm baffled why objects seem so much brighter. We've tried a Max camera and it's still bright .. is it due to calculations dealing with much larger numbers when using the Vray sun ? ..

thanks
ben

[Dariusz Makowski (Dadal)]

aaa Right... so basically u need an alpha... how about 2 renders then ? 1 with visible to camera off, and second very simple in scanline B&W just to get alpha for characters.... as a walk around method... I dunno about the mattte isse never tryed it.

[bencowell]

Yep that's what i'll have to do, I'd really like to know why a method I normally use without an issue seems to give such different results with vray sun. Does anyone have any idea ?

thanks
ben

[dellis]

That is strange! You should have a look at this if you haven't already...won;t help the brightness thing...but may help get around it better!

http://www.lukashi.com/script.php

[bencowell]

Yep we're already using RP Manager, to be honest workflow isn't really our issue. It's that the passes we usually create don't seem to behave normally using Vray Sun. Is there anyone from Chaos Group that could tell me if this is a known limitation ?. If there was a work around it'd be very useful.

cheers
ben

[vlado]

There is an option in the V-Ray object properties called "No GI on other mattes", try turning it off and see if you get what you need.

Best regards,
Vlado

[bencowell]

Hi Vlado,

Thanks for your response, what does this checkbox do ?. It does seem to fix the intensity issue but means that the entire scene's GI has to be calculated at render time rather than just the character.

I'm interested to know why we've only encountered this issue with vray sun rather than the usual vray lights ?

All the best,
ben