Render elements include/exclude

V-Ray V-Ray for 3ds Max General
1

I’m rendering an animated sequence with AO as an ExtraTex element and zdepth. My camera is looking through some glazing which is causing some problems for these passes; ie the AO and Z do not take the transparency of the glass into account.

It occured to me that it would be great if I could include/exclude objects from both these passes. Is this possible within the architecture of Vray? or am I forced to setup a seperate render with the glass objects hidden.?

2

An exclude/include list is not what you want as it will not work for this purpose.

In V-Ray 1.5 SP3, the “Affect alpha” option for VRayMtl has been renamed to “Affect channels” and the third possible value (“All channels”) will allow all render elements to see through the glass.

Best regards,
Vlado

3

there’s an affect channels dropdown in the refraction properties of the vray mat, it lets you specify if you want the transparency to affect only the alpha or every other channel. set it to all channels and it should solve the problem.

edit:
well, what vlado said.

4

Fantastic stuff… vray always exceeds expectations :slight_smile:
That works perfectly.

Thanks again.
p.

5

Ok, that’s working great. Thanks for pointing out the parameter.

One problem I’m having now is that the AO pass seems to be getting affected by the transparency of the glass layers. I think in C4D the parameter to tick would be “ignore absorbtion” which would stop the AO pass from being tinted white by the glass layers.
I can probably extract the AO behind the glass in post and apply it seperately to the AO in the foreground, but it would be nice to be able to aboide this process. There’s probably an option in Vray I’m not aware of!

Here’s the straight 8-bit AO pass:-

Here’s the re-exposed 16-bit AO pass:-

and here’s the EXR for those that want to see the actual gamut of the AO pass:
http://www.reformstudios.com/01-img/forums/ao.exr

6

Currently there is no way to do that, but I’ll make a note to look into it.

Best regards,
Vlado

7

Thanks Vlado.

Whilst I’ve got your attention, can you tell me whether the AO pass within an extraTex is any faster than rerendering the scene as a straight AO pass? I would assume that it adds the same duration to the rendertime, but I’m curious to know if you were able to achieve any optimisations.

8

There might be less overhead on scene preparation and such like, but the actual computation time is the same.

Best regards,
Vlado

9

This is probably a stupid question, but what the hell.
If my limited understanding serves me correctly, is there any potential to reuse any sampling generated by the IR map HSPhere sampling to optimise the AO pass?

As you can probably tell, I’m talking about a subject I know little about! :wink: Just curious.

10

Just posting here to remind others and myself! that doing this doesn’t automatically mean vraydirt in extratex will ignore your glass. You ALSO have to tell it to exclude the glass objects.

11

I’ve just realised we’re having the same issue, with the vray dirt AO working through glass, but only with a lower exposed version, as Patrick said. I guess for now the only option is to use the normal exposure and use a second version and mask it in for the behind glass.

I’d be keen to see this fixed!!!