3DS Max + Vray 3.5 - Issue in saving the Alpha channel

[kumuduthenuwara]

I'm having an issue when I export alpha channel for glass materials as I explain in the attachment/picture.

Kindly help me.

[Francisco Penaloza]

You need to save a separate Mat ID pass and a Multimatte element to solve that problem, one will work with transparency the other one will omit it, so you can select the whole glass.

[kevin miller]

I think my issue is the same as this original poster so I am trying to help others by posting here but maybe I am wrong. I want to be able to change the background in post production that shows through the exterior windows from an interior rendered view. As one is standing int he interior, you are looking through an interior glass partition and then the exterior window. Exporting the rendered image with an alpha channel is making a mess as it treats All of the windows as transparent. I need the first interior window to stay the way it is rendered while the exterior window should have the alpha so I can switch out the background image that should then show through the interior window.

 

If this does not make sense, maybe the attached draft rendering will.

[Francisco Penaloza]

You have to use a combination of MatID.

First assign different mat ID to each glass, then on the glass for the background be sure to Affect channels: All channels or Color+alpha.

Crete a Material ID pass, then create a MultiMatteElement. and add the Mat id of those glass panel, be sure to select the include/exclude option the glass panel in the background.

now when render you'll have an alpha map with the cut out of the back window, or the one behind the first glass and also you'll get a multi matte with colors of the foreground window.

[kevin miller]

Hello Francisco,

 

I just saw you responded to my post. I did not have notifications on so I did not know but thanks for the information. I just created a new post since I had continued having issues with this. Is your solution what will address the information disappearing behind my interior glass alpha?