How to make glass render black environment with VRay sky?

[davexl]

Forgive my tired and foggy brain...

I want to render an interior using sunlight and VraySky. And I want the window glass to be invisible to the VraySky skylight. (not the Sun, Sun is working fine through glass)

I want to comp in a background photo later of the view out the window, so I need to render against black. (If I just let the background blow out to white and post multiply later I lose internal window reflections.)

If I turn off the 3dsmax environment slot, and use VRaySky in the Vray Environment override slots - in both GI and Reflection/Refraction, not in Refraction environment override slot & use black - I get what I want, nice black environment perfect for comping.

BUT I lose all VRAY skylight coming in through glass windows - no skylight shine reflected on floors etc. (unchecking visible to refraction/Visible to GI on glass objects does not work)

To sum up - without doing a separate render pass, how do I:

Make glass visible for reflections
AND
Pass through Vray Skylight
AND
Black background?

[AlexP]

Was trying to work this out myself yesterday.
Im sure in the past it was as simple as using environment refraction override in the render settings, but it's been a while since i had to do it.

Need to know also.

[dlparisi]

I'm not in front of a computer right now so I may be remembering wrong but.... make vray override material with your normal glass in the base slot and copy that glass into the refraction slot. For the new refraction glass, add an environment override of vray color set to black. You may need to make the glass not visible to reflect/retract but I can't exactly remember.

[davexl]

I'm not in front of a computer right now so I may be remembering wrong but.... make vray override material with your normal glass in the base slot and copy that glass into the refraction slot. For the new refraction glass, add an environment override of vray color set to black. You may need to make the glass not visible to reflect/retract but I can't exactly remember.

Cannot get it to work, I tried with and without checking not visible to refraction (have to leave reflection on, as it is needed)

(But thank you for the tip, I had completely forgotten the override material - it has given me some ideas to try.)

[dlparisi]

Just checked this in front of a computer... it works for me just creating an override material that has a a duplicate glass in the refraction slot and a black color in the environment slot.

Is your glass by any chance a single plane? This seems to kill it working for me. As long as the glass is a box (it has an inside and and outside) it works just fine.

I also typically remove any glass from "visible to GI" in it's V-Ray properties. This allows any skylight to easily get through the glass.

EDIT: BTW, your technique of replacing the max environment slot with the ones in the VRay environment roll-out also kills any reflections or highlights of the glass when seen in reflections (e.g. a floor reflecting the window).

[davexl]

worked!!!

Silly me - I forgot to turn off the environment overrides - now it is working as planned. The only minor hassle is seeing though on open door - but that was easily fixed by creating a distant box with a similar material.

Can't thank you enough mate - really appreciated.

[dlparisi]

Glad to help. I struggled years ago to find a solution to this for just the reasons you mentioned. I think this was before the override material was available so I never got a suitable solution.

[davexl]

Well this is awesome, no fudge second pass with hacks to get the glass right - I have a climbing vine backlit in the sun seen both through window glass and through an open door, and this was needing a bunch of special attention... not anymore.

Have I thanked you recently enough?

So including HAL9000 you have at least two fans.

[dj_buckley]

This is exactly what I need, but I'm using a dome light with HDRI and the above solution doesn't seem to work. I want the HDRI visible in all object reflections (i.e. floor, polished marble worktops etc) but I want the glass to just have a solid black colour. If not, then you get that horrible half sky/half black hdri reflection

I've attached an image below, I want to get rid of the sky in the red, but keep the reflections in the blue

[dlparisi]

This is exactly what I need, but I'm using a dome light with HDRI and the above solution doesn't seem to work. I want the HDRI visible in all object reflections (i.e. floor, polished marble worktops etc) but I want the glass to just have a solid black colour. If not, then you get that horrible half sky/half black hdri reflection

I've attached an image below, I want to get rid of the sky in the red, but keep the reflections in the blue

[ATTACH=CONFIG]30912[/ATTACH]

But isn't this correct? The windows need to reflect something besides black otherwise the opposite would happen, you'd end up with the windows reflecting the interior of the room with black holes where the window reflections are. IMO this will look wrong when you try to comp in the background as you'd end up with darker holes where there should be brighter spots where the sky is "doubled" (the sky seen through the glass plus the reflected sky).

Regardless, to achieve what you are after I think you can bypass the whole override material and simply put a black color into the glass environment slot along with unchecking "visible to reflections" in the Vray Properties dialog for the glass.

[dj_buckley]

You're correct, it is technically correct, the main problem is with the HDRI itself, being half sky, half black. It would be more consistent for the comp if it was all black. Otherwise I get the inverse again, if I comp into that as it is, then the lower half of the backplate becomes much darker than it should. The even bigger problem being the blaustrade glass beyond, if the horizon were to sit perfectly along the top of that then I could get around it, but currently it sits midway through that glass making it even more difficult to balance out the backplate. Hopefully that makes sense. The ideal situation is just rendering with the backplate on a mapped plane - I just don't have the backplate just yet.

[dlparisi]

Got it. I think that in this case you'll need to exclude the glass from the Dome light and mark the glass as not visible to reflections/refractions. Should work fine for simple window glass. I think....