Pref Pass in Arnold

[pixelmonk]

What's the correct hook up for the Pref pass for Arnold?    I'm trying to get an object position reference.  I  tried aiUserDataVector > aiUtility and then applied that to the Pref AOV.   I then turned on the export tangents and reference tangents for the objects.  It looks like that method shows any object on a particular angle to have the same RGB values.  For instance, two boxes stacked in Y will show the same pink on one angle and blue on another angle (side).   That doesn't seem to right though?  It should be an Object XYZ, so even stacked boxes should have different values?  I can't find any tangible information on using the Pref pass to extract positional data as a utility pass for Arnold.

Also, if there is a way, can it be less laborious than finding each and every object and turning off their export tangents (or is that a scripting thing I need to do)?

[Stephen.Blair · Accepted solution]

Hi

Pref is in world space. 

And it's a builtin AOV so you wouldn't apply anything to it. 

It's been awhile, but I think you can get object space positions with the Sampler and feed that into a custom AOV.

You could use the Attribute Spreadsheet to bulk edit Ai Export Tangents

[pixelmonk]

yeah that seemed to work.    I piped a samplerInfo >  Point OBJ > to Color of a aiUtility and then applied that as a shader for a custom AOV.   Thanks!

[NandoStille]

To get the "Pref" AOV working, create a "Texture Reference Object"

To create a Texture Reference Object

[yogi]

Hi,

I'm running into this issue as well in Arnold 5. I've done the suggested fix above and it seems to work on animated but non-deforming objects. Anything that is rigged or animated with a deformer will deform out of the object space colors of the P pass. Is this something that should work with this solution or is there another workflow that can make a Pref pass work on deforming objects? Any advice would really help!

Thanks,

-Connor