Material ID and Transparency

valerostudio · 4 Sept 2012, 19:05

Any tricks on how to get the material id for a 100% clear glass to show up in the VFB? Seems like the materiald id takes the transparency into account.

andybot · 4 Sept 2012, 19:19

yeah, I've run into that problem too. I put a plane behind my windows in the interior, set it to a new matID...

valerostudio · 4 Sept 2012, 19:40

So you do a separate region render after your beauty pass is done?

andybot · 4 Sept 2012, 19:50

erm, no. This is only with an exterior model, so it doesn't matter so much what's on the interior. Don't know any more than that, I've not used material ID for windows where I can see the interior. Maybe a reflection pass can help you mask your windows out?

thomthom · 4 Sept 2012, 21:26

Can you render out a pass with transparency disabled...?

andybot · 5 Sept 2012, 13:06

@valerostudio: I figured it out! - you don't have a refraction layer do you? It works fine with a refraction layer...

Not to mention - it gets weirder if you have an ID color for the glass - it overlaps the ID color of the other IDs. see second matID map example.

Here are my material settings:

thomthom · 5 Sept 2012, 13:18

This smells like bugs all over the place!

thomthom · 5 Sept 2012, 13:30

@andybot said:

Note that the amount of transparency is very different with a single layer of glass.

Isn't that the fog?

andybot · 5 Sept 2012, 13:34

no, my fog color is pure white. There's two layers of reflection instead of one.

Edit:
Oh, and the dark blue glass is not completely transparent. This is a material I use for exterior renders when I don't want to see in the building.

andybot · 5 Sept 2012, 13:41

Buggy, yes, just one of many
c'mon new beta!!

One trick - if you are using a single layer of glass, is to change the refraction IOR to 1.0 to avoid distorting objects behind the glass.
having the refraction layer works with both single and double thickness glass for MatID.

Note that the amount of transparency is very different with a single layer of glass. (Edit: I am using a semi-transparent material for the dark blue glass instead of fully transparent.)

valerostudio · 5 Sept 2012, 14:40

Flipping A! Nice work to finding a trick for this pain in the butt bug. Seriously need this new beta.

valerostudio · 5 Sept 2012, 19:24

The AA on the glass id channel does screwy things. Anyone know why this is?

valerostudio · 5 Sept 2012, 20:04

I assume its a product of refraction. You can see the AA on the green edge compared to the red edge of the glass. Choppy and weird. At least this is a decent workaround. Thanks guys.

gparadis · 25 Jan 2017, 15:09

Reverse question - is there a way to exclude 100% transparent material from the material ID render ? Say I have a texture of a tree where the foliage is opaque and an alpha channel masks what's not needed. Material ID still considers the transparent surface as a different material.

When a lot of objects are in background, selection is not optimal.

Thanks