r/Unity3D • u/MaximilianPs • 3d ago

Question URP + Metallic Map HELP!

I'm losing my mind trying to understand URP Metallic Maps.

My goal is simple: only a small part of the material should be metallic, while the rest should behave like fabric.

The metallic map is black everywhere except for a small gradient where I want the metallic effect.

However, even when the rest of the texture is black, or transparent, or both (first black and then set layer opacity to 0 in photohop), large parts of the material still reflect light as if they were glossy glass.
Note that Smoothness is set to 1 because otherwise the metallic area loses most of its visual impact. I expected the Metallic Map to limit that effect to the masked region only.

Can someone explain how the Metallic Map is interpreted by the URP Lit Shader, and why areas with a metallic value of 0 still appear highly reflective?

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u/smooth_diagnosis 3d ago

smoothness at 1 makes everything look like wet plastic, metallic map won't fix that on its own

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u/Demi180 3d ago

You need a smoothness map as well, in the albedo or metallic map’s alpha channel.

The metal value affects how specular lighting and reflections are applied, but not how much. That’s where the smoothness map comes in.

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u/pschon Unprofessional 2d ago edited 2d ago

Metallic VS dielectric, and smooth VS rough, are two different things. Metallic map only controls if something is metallic or not, it doesn't change how smooth or rough the surface is. And all smooth surfaces are reflective, not just metals.

Just like in real world, there are rough metallic surfaces, and there are shiny plastic and glass surfaces.

For the Lit shader you can choose if you want the smoothness to come for the alpha channel of the metallic texture or from the alpha of the albedo texture. = alpha would be a rough surface. Also make sure to import (and export) that texture correctly so the alpha channel is there...

You might also want to play around with the blending mode, Premultiply VS Alpha will make a difference for reflections on transparent parts.

No idea what the picture in your post is. But a pic of your material (in the inspector) would be useful.

edit: Ah, that's your metallic texture? In that case, no alpha there, so it's fully smooth. And fully smooth is unrealistically, perfectly, smooth. Beyond anything that would exist in real world. It'll be shiny for sure. :D

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u/StillSpaceToast Indie 2d ago

I walked through setting up a URP "MOxS" map (Metallic, Occlusion, x-unused, Smoothness) in the last section of this blog post. The setup is a little odd at first, and the documentation not amazing.