refractive IDs in Arnold

[Ryan O'Phelan]

Hey guys,

I'm not an Arnold guy, but doing an Arnold job. yay.

I have some glass, and I need an ID AOV of stuff refracted in the glass. For instance, I need a matte for the wine in a wine glass. 

Anyone know how to do this off hand? 

Thanks,

Ryan

[Olly Nash]

Hi Ryan,

this doc explains it well:

https://support.solidangle.com/display/AFMUG/Using+Custom+AOVs+to+Create+Mattes

and this vimeo is helpful too:

https://vimeo.com/70929016

Olly : )

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[Ryan O'Phelan]

Thanks Olly,

 I'll try it that way. I didn't realize it was different from using an aiwritecolor node in a shader, which does not refract.

[Ryan O'Phelan]

I just tried it this way, and it definitely does not work. 

It does add a new AOV and renders the new shader when seen directly, but not when refracted through another piece of geometry. 

Is there something I need to do to the other geometry or shader to allow AOVs to be rendered through them?

Thanks,

Ryan

[Ryan O'Phelan]

I found a toggle on the ALshaders ID section to transmit AOVs.

This made me realize what was really going on. The "wine" shader is also transmissive, and the diffuse is off, and therefore does not show in the ID matte because it is just the background refracted through the wine, being tinted by the transmission color. When I make it opaque, it shows up in the matte. Adding diffuse color lets the AOV ID work, but I'll bet there's a bette way to do this. 

R

[Olly Nash]

Hey Ryan,

Oo, good toggle switch to find! Thanks for sharing.  

Your approach makes sense and as no-one has anything else to offer, I think you're doing the best way possible!  If you really need that extra matte, you might have to admit defeat and do it in another pass!!

Good luck!

   Olly : )

   +44 (0)7977 407613

[Ryan O'Phelan]

Thanks Olly, 

I have concluded that transmitted aovs should be done in their own layer. If they are done in the beauty, then they will transmit all other aovs, and make a mess. An expensive mess too.

R

[Olly Nash]

Oh yes, good point!  Thanks for sharing your findings dude : )