topic Re: Alpha Gain parameter not working with Arnold in Maya Shading, Lighting and Rendering Forum

Alpha Gain parameter not working with Arnold

litote — Wed, 01 Nov 2017 18:32:49 GMT

I am rendering sprite particles in Arnold and am trying to adjust the alpha of the particle image I used to make the sprite more transparent. In Hardware Render 2.0 you can do this by adding the "alpha map" (I am using a PNG) to the Transparency field an adjusting Color Balance-Alpha Gain parameter that is below it.

But If I use an aiStandard material for rendering in Arnold and put the alpha map in the Refraction-Opacity parameter to create the alpha transparency, I find the Alpha Gain has no effect on adjusting it as it does with Maya Hardware 2.0 renderer.

Is there a way?

Re: Alpha Gain parameter not working with Arnold

mspeer — Wed, 01 Nov 2017 20:05:32 GMT

Hi!

I am a bit confused by your explanation, but for Opacity in Arnold in general:

1. Shape node, Arnold tab disable Opaque

2. In Arnold material use Geometry -> Opacity

Re: Alpha Gain parameter not working with Arnold

litote — Wed, 01 Nov 2017 21:13:07 GMT

Geometry -> Opacity? Do you mean Refraction-Opacity?

Re: Alpha Gain parameter not working with Arnold

mspeer — Wed, 01 Nov 2017 21:20:07 GMT

Hi!

No. Tab Geometry, then Attribute Opacity.

Re: Alpha Gain parameter not working with Arnold

litote — Wed, 01 Nov 2017 21:26:55 GMT

Tab Geometry? Where exactly?

Re: Alpha Gain parameter not working with Arnold

mspeer — Wed, 01 Nov 2017 21:42:16 GMT

Hi!

In Arnold material like aiStandardSurface.

Re: Alpha Gain parameter not working with Arnold

litote — Thu, 02 Nov 2017 06:35:47 GMT

I see no "Geometry" tab in the aiShader. I see only rollouts... Matte, Diffuse, Specular etc. The only Opacity parameter I see is in the Refraction rollout. Where are you seeing it exactly?

Re: Alpha Gain parameter not working with Arnold

mspeer — Thu, 02 Nov 2017 18:51:30 GMT

Hi!

It looks like you are still using Arnold 4 which doesn't have aiStandardSurface material.

So Opacity is to be found at an other place. (i can't test this anymore)

Please read the Arnold for Maya User Guide for more details.

Re: Alpha Gain parameter not working with Arnold

litote — Sat, 04 Nov 2017 15:59:52 GMT

I upgraded to Arnold 5. The same control ha no effect either.

Re: Alpha Gain parameter not working with Arnold

mspeer — Sat, 04 Nov 2017 19:15:01 GMT

Hi!

Please upload the scene-file + texture(s) for particles.

Re: Alpha Gain parameter not working with Arnold

litote — Sun, 05 Nov 2017 08:08:28 GMT

Hello,

I have attached the scene as a zip file. It includes the texture file.

The Color Balance-Alpha Gain and Alpha Offset attributes in the Geometry-Opacity parameters where I added the alpha map (click on arrow next to Opacity slider in the aiStandardSurface shader tab) have no effect. They did work with Maya's Mental Ray and Hardware 2.0 renderers, but not for the aiStandardSurface shader in Arnold 5.0.0.2 (MtoA 2.0.0.1).

Re: Alpha Gain parameter not working with Arnold

mspeer — Sun, 05 Nov 2017 18:09:07 GMT

Hi!

Alpha Gain only affects Alpha Out, but you are using Color Out.

Check in Node Editor or Hypershade.

Re: Alpha Gain parameter not working with Arnold

litote — Mon, 06 Nov 2017 07:09:57 GMT

Hello,

What connection do I need to alter in the node graph? I have attached the screenshot of the current graph.

Thanks

Re: Alpha Gain parameter not working with Arnold

mspeer — Mon, 06 Nov 2017 18:29:34 GMT

Hi!

Out Color+ ----------->------------ +Opacity

Re: Alpha Gain parameter not working with Arnold

litote — Tue, 07 Nov 2017 07:03:12 GMT

Did you look at the image of the node setup I attached? Is it correct? I have the map I added to the Geometry-Opacity field linked from Out Color to Opacity but the Alpha Offset has no affect.

Re: Alpha Gain parameter not working with Arnold

Stephen.Blair — Tue, 07 Nov 2017 16:51:47 GMT

Alpha Gain and Alpha Offset apply to the alpha value output by the MayaFile node.

Re: Alpha Gain parameter not working with Arnold

mspeer — Tue, 07 Nov 2017 23:28:39 GMT

Hi!

"from Out Color to Opacity but the Alpha Offset has no affect"

Correct, Alpha Offset has no effect on Out Color.

Alpha Offset has only effect on Out Alpha.

So use Out Alpha.

Re: Alpha Gain parameter not working with Arnold

litote — Wed, 08 Nov 2017 07:35:22 GMT

Thanks for taking the time to post this screenshot Stephen. I couldn't get the output to connect to the Opacity as I didn't realize you had to twirl it open and connect to the RG and B. Presumably you use the Alpha Gain in the Color Balance rollout to adjust the alpha?