Metallic Workflow clarification

Hey all

Documentation says Metallic levels for the material controlled in the Red channel and smoothness by the Alpha channel, in each case of the texture.

Why do we have Smoothness Source Albedo Alpha and Metallic Alpha? Metallic Alpha doesn't make sense if we say metallic is in the Red channel. I can't ignore this setting because using one of the other has an impact on the material result.

Also, when I use a darker gray color on the alpha channel of Metallic map, the material darkens - but I would have thought it should only affect the smoothness and not the color tone?

Can someone please shed some light?

Thanks a bunch!

 

"Metallic Alpha" refers the alpha of the texture that defines the metalness (not the alpha of red, which would indeed make no sense). Basically you can choose to have smoothness stored either in your main texture or in some secondary texture that also stores metalness.
If you go for the secondary texture approach (which I personally always use), its format should be Smoothness (Red), Occlusion (Green, optional), Detail mask map (Blue, optional), Smoothness (Alpha). Because everything is packed in the way that unity expects it, you can put this one texture into the occlusion and detail mask slots if you want to.


Regarding the darkening it might just be something specific to your scene lighting. As you make the material rougher the reflections will become softer and dimmer, which means potentially darker in some places. A screenshot would help.

 

Hey @Tartiflette thanks for this. I am going to try this and get back

If I may clarify, you mean don't add any texture map to the Metallic map slot, but add texture map to the Occlusion Texture map with R(Metallic), G (Occlusion), B (Detail Mask) A (Smoothness) ? Then the Unity documentation falls quite short

With the above setup I am guessing I can use the metallic and smoothness bars to set the metallic and smoothness desired levels too ?

Thanks a bunch for your help, Sergio

 

No you put that texture with all the channels into the metallic map slot, the occlusion slot (if needed), and the detail map slot (if needed, but you probably don't). It's basically a multi-purpose texture.

 

It should be noted the Standard shader's detail mask uses the alpha of the texture supplied, not the blue channel. The above packing only works with custom shaders where you've defined the packing yourself.

Otherwise Metallic (R), Occlusion (G), Smoothness (A) does work with the Standard shader. Optionally you can store the height map used for parallax offset mapping in the green channel.

 

That's clear now @Tartiflette @bgolus , very helpful and poweful to reduce map weights

Thanks a bunch for your help !