Using maya + arnold 4.2.13.4 Rendering a shader with opacity in AOV pass. Opacity is not computed at all. Same shader in beauty pass works perfectly. What's the problem?

[Riccardo_Zanettini]

Not sure what's wrong but this looks like and Arnold bug. Opacity is not there at all...

[Riccardo_Zanettini]

more details

opaque uncheked

texture works fine (otherwise beauty won't be working)

[Riccardo_Zanettini]

not a lot of people helping out in this forum

[Stephen.Blair · Accepted solution]

Hard to tell exactly from that brief problem description, but I think you need to use an ai write color node, and enable Blend

[Riccardo_Zanettini]

let me rephrase the problem

I have a shader with opacity that is driven by a texture.

If I render that shader in the beauty AOV the transparency is working.

If in the shading group node I plug the same shader in a custom AOV (let's say beauty2) the opacity texture of the shader is ignored and the alpha is solid.

I hope this helps!

[Stephen.Blair]

When you "plug the same shader in a custom AOV" are you using an ai write color node? Do you enable Blend?

[Riccardo_Zanettini]

no I am not using a write color node... not sure why I would have to use and ai write color node can you please elaborate?

[Riccardo_Zanettini]

also does the ai write node need to be plugged into the shading node?

[Riccardo_Zanettini]

shading group node that is

[Riccardo_Zanettini]

what you suggested works really well... thank you! I am just puzzled about why this node is necessary, Arnold doesn't process any of the shaders piped into the shading group node other than the surface material?