Maya GPU opacity shows mask outline

[Anonymous]

I could swear this had been working earlier today, but suddenly I started getting the outline of the opacity mask. Opague is still unchecked, I've checked that the file is black and white without transition. There is only the diffuse and the opacity connected at the moment.

The CPU will render the opacity mask just fine, but the gpu will make the black part of the mask semi transparent for some reason. Playing with the offset doesn't change anything. I also tried deleting the preferences.
Also tried adding more Adaptive samples etc.

This is with the current Arnold.

CPU

GPU

Viewport

[Labyrinth_Visual]

Really?  3 Years and nobody responded?!?!?  I'm having the same issue right now.  Did happen to find a solution?

[thiago.ize]

What version of Arnold are you using? If it's the latest (currently Arnold core 7.1.2.0) and you still have this, can you post a simple scene that shows this problem so we can investigate?

[Labyrinth_Visual]

Well, I don't know what version the other person is on, but I'm on 5.1 mtoa I believe.   Just found a fix for the issue.  When I removed the texture on the mesh that was behind the object, the issue disappeared.  So I plugged all my texture maps back in (albedo, roughness, normal), then unplugged one by one - the issue disappeared with the normal connection being broken. 

Found out, you have to adjust the color offset (in color balance) for the normal map file all the way to white.  This is for the geo and material behind the object that has the alpha, and seemingly, the issue.  In short, the issue is the color offset behind the object using alpha for tranparency, in my case, terrain and background.  Would have never thought that.

[Labyrinth_Visual]

BTW, realized that negated the values of my normal map (duh).  So setting the previously mentioned settings back, and changing the "use as" method to bump, instead of  "tangent space normals" did the trick too, keeping my normal map working properly as far as I can tell.