Control metal reflection color with PR Shader and an Albedo input texture

Question

I have a metal node setup with textures from texture.com which produces a reasonable metal material with Principled Shader (2.79)- but the 'Silver' reflection is what I don't understand. How do you control the metal reflection color - let's say I wanted a Gold ball or a Blue ball - if the base color input is already used?

The base color is already input from the Albedo image, but it's application to the surface is controlled by the 'metallness' image (I think) which says which parts are metallic and which parts dielectric. If the Albedo input is only applied to the parts of the surface that are dielectric/diffuse..what's controlling the metal reflection color and how do I control that?

Answer 1

The metalness workflow uses an Albedo map to define both the diffuse and reflectivity content.

• for insulators the diffuse is taken from albedo, reflectivity color is white and the amount reflected is small (about 4%).

• for metals the diffuse is black, reflectivity color is taken from albedo and amount reflected is 100%.

The metalness map is then used to define how much the material is an insulator or a metal and so how the albedo color is used.

It is setup like this to save texture space, which is important to game engines and to render engines alike. In the specular workflow the diffuse and reflectivity colors are set explicitly with two unique texture maps. You can make PBR materials with both approaches, more on this is nicely written on Marmoset's site.

Answer 2

A single complementary texture/pattern can drive the albedo color of the dielectric parts and metal reflection color. The patterns of the abedo texture that drive the metal reflection color must correspond to the complementary patterns of the metal texture that drive the metalness. In your case, even though they are 2 different seemingly unrelated textures, they were probably generated from the same base texture.

Here is a simplified example within blender and a color ramp to apply the albedo and metal reflection colors based on a single pattern: