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Matthew Gifford avatar image
Matthew Gifford asked ·

Custom arnold shader AOV Arnold 5 (arnold shader driver)

Back in the days of Arnold 4 I used to be able to create a 'custom AOV' in my scene and then directly plug a full 'aistandardsurface' into the 'shader' input on the 'AOV driver'

This allowed me to have a separate aistandard shader as a custom aov, unfortunately in arnold 5 this seems to just return either a flat colour or black,

Example: I have a fully textured and shaded character but I would also like to output a simple clay shader of the same character in a custom AOV

I've been looking into this post which seems to get close to what I'm after, any ideas how to set this up?

https://answers.arnoldrenderer.com/questions/6307/shader-custom-aov.html

Thanks!

arnoldshaderaovarnold shader network editorscene
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Stephen Blair avatar image
Stephen Blair answered ·

Standard Surface doesn't return a color, so you cannot use Standard Surface to write to a custom AOV (the AOV write shaders need a color value).

In Arnold 5, Standard Surface returns a closure, which is evaluated later by Arnold and used for LPEs.

You can use shaders like Utility or Flat to write to a custom aov.

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Hmm, this is a big problem.

Can't use Flat or Utility because they don't accomodate displacement or opacity which Standard_Surface supports. So if we just want to generate a simple holdout matte AOV, what used to work no longer does.

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Dave Cook avatar image
Dave Cook answered ·

@Amro Haroon Just looking into this a little here and although you can't plug a StandardSurface into a custom AOV, there are a more shader options in the utility shader than I remember - you can have lambert, plastic or metal and you can also add texture to the color property. This was enough for what I wanted as an secondary material.

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Amro Haroon avatar image
Amro Haroon answered ·

I'm facing this problem too, did you figure it out?

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Matthew Gifford avatar image
Matthew Gifford answered ·

@Stephen Blair So in arnold 5 there is no way to write a full shader to an AOV as possible in arnold 4?

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Shaders that return closures cannot write to custom AOVs

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