Refracting and Reflecting things in ObjectID

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  10 October 2012
Refracting and Reflecting things in ObjectID

Hi all,

Last year I was working with Arnold and XSI and we had a pass that showed the Object IDs of things through refractions and in reflections.
Example of what vray does with object ID (very basic scene just to help explain what I'm trying to do so please dont crit scene)


There are three objects in scene, one of the objects is inside the other but is visable through the refraction and two of the objects reflect in the floor object. Is there a way to get them to show in an object ID way so I can grade them in comp, i.e. 1 ID for the refracted object that will grade the refraction and the reflection etc.


  10 October 2012
in the vray material there is a affect channels dropdown in the refraction section. when you switch from "color only" to "all channels" the objects ids get visible through the refraction.
  10 October 2012
I tried that but it did not work
  10 October 2012
You could try doing it by making separate render of it (your own custom pass).

Just give the object inside the glass a self illuminating material. You'd probably also have to adjust the refractive material to have no color.

Ideally you could make a state set of it. Havent worked with state sets yet, so i dont know if its possible, but from what i've seen i think its possible (in fact i think it was meant for this kind of things?).
  10 October 2012
The good old raytrace materials support this by default ( reflection/refraction of material id's ).
You might try some freeware plugins ( render effects) which pull the object id out of refracted/reflected regions. One is Pavel Kuznetsov's Ky_G-Corrector, which pulls Object/material ID's behind transparent objects, allowing a certain threshold value

Or another one by the same author Ky_Throughout:

those only work for refraction though...

so for a simple floor reflection, you might get away with using the raytrace material for the floow in vray

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Last edited by spacefrog : 10 October 2012 at 05:18 PM.
  10 October 2012
Originally Posted by Lsdinc: I tried that but it did not work
It will not work with the object ID, but it will work with the multimatte element, if all you need is a mask for your object.

The Raytrace material will not work well with V-Ray and I would recommend to avoid using it.

Best regards,
  10 October 2012
Originally Posted by thev: It will not work with the object ID, but it will work with the multimatte element, if all you need is a mask for your object.

Is there a vray multimatte or is it just the standard one. I tried it and it did not work, can you explain a bit how to set it up or I can send you the file?


  10 October 2012
I got it I got it, thanks a ill for all your help.
  10 October 2012
Originally Posted by Lsdinc: I got it I got it, thanks a ill for all your help.

can you tell us how you ended up doing it?

It could en up being helpfull for us also.
  10 October 2012
Apologies, yes of course.

I used the multiMatteElement render element.
I ticked the boxes that are unticked in options for element.

I set all the materials with a material ID in the Slate view
and rendered.

It only really works with clear refractions, so no fog.

It does not work for reflections either but it is handy if you need a mask from some colour grading after.


  08 August 2013
Thumbs up

Hi. I've found another way to get the Object ID look through a reflective and refractive object, even with Fog. I've changed the Affect Channels in REFLECTION section to "Color Only" and in REFRACTION I leave it as "All Channels". As my material is for a Glass Door, it has a tiny reflection that makes the object behind that object a little darker. Hope this be useful for someone, as this could save some render setup time

Last edited by lesgauthy : 08 August 2013 at 04:30 PM. Reason: Misspeling
  08 August 2013
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