I can´t find a solution for rendering a correct alpha channel with my glass material. I´ve set everything according to threads in this forum and tried several things but still VRay does not render correctly.
As you can see in the rendering, there are windows on the back side of the house. The front windows render correctly in matters of alpha channel, but everything behind is also transparent, meaning the window frames are not visible in the alpha channel.
Does anyone know a solution for this ?
Is you glass set to a matte in the vrayproperties or a wrapper?
What is your glass material? Does it have the “affect alpha” checkbox?
Best regards,
Vlado
Please see material screenshot above. Its the vray material with refraction glossy 1.0 (as mentioned in other threads and vray help) and affect alpha checked…
does enabling fresnel for the reflections make a difference?
2nd RErender’s suggestion..
No, Fresnel on / off makes no difference.
It seems that irradiance map is rendering the alpha channel correctly, but not light cache and not the final render pass.
any more ideas ?
I´ve read that SP3 might solve this problem. Any chance to get access to the beta version ?
I´ve also tried this, but the result is an alpha channel with wrong
geometry in it. So this also does not work…
Sp3 resolves the alpha problem with blurry refractions.
In your case it shouldn’t make any difference, imo.
yep, it should be working from what i can see.
try taking off interpolation on the refraction, theres no need for it anyway if the glossiness of the refractions is at 1.0
Thanks, I see. But what might be the problem then ? I don´t see why this isn´t working …
Can you post a scene? Even just a stripped down one with the glass, walls, and a ceiling…
make sure glass is not a plane (1 sided).. ?
or that you have no coplanar faces in your glass objects…
Thanks for your replies!
The glass windows or not 1-plane objects.
I´m not sure how to check whether the windows have coplanar faces.
Actually I don´t exactly know what this means …
I´ve uploaded reduced scene for testing …
http://www.pixel-sound.de/clients/download/CaseStudyHouse\_for\_alpha\_testing.zip
Thanks!
very strange.. I made a new glass material, used the select by material from the the material editor to select your glass objects and applied the new material… it worked… BUT, then i tried opening your scene, selecting the glass objects and just re-applying your own glass material, and that worked too!
So basically, no idea what you did wrong, but try just re-applying the material to the objects!
Although your active material in the material in the material editor, “Glass_Fenster”, looks like it’s at the top level it’s actually the base material of a VrayMtlWrapper (they’re both named the same). You can tell this by eyedropping the material from the glass. In the wrapper the alpha is set to -1 which blacks out anything behind it. Just remove the wrapper (drag the base material map up to an empty slot) and reapply it.
Heh, had this solved with one post and less than 1 hr of trouble 
queue little pink embarrassed smiley
