Metal material references:https://experienceleague.adobe.com/en/docs/substance-3d/general-knowledge/asm/metal-material-references#bit-srgb
In their Novel aspects of the adobe standard material article. It says:
For the metallic Fresnel term, we use a modified version of Naty Hoffman’s F82 model [9], which was in turn
based on the Lazanyi–Schlick approximation [16]. We informally call this new formulation the “F82-tint”
model because it allows the edge tint to be applied multiplicatively rather than being used directly as the
reflectivity.
This formulation has the useful new property that it reduces to regular Schlick reflectivity when the edge
tint is set to white, which allows white to be used as a universal default value (Figure 4). Like the original
F82 model, this model can be used for creative control as the edge tint is clearly visible regardless of the
selected colors, and it can approximate the real Fresnel dip by using a custom reflectivity at approximately
82◦(Figure 3).
In our formulation, the edge cannot be made brighter than what would be produced by the standard Schlick
term (monotonically increasing reflectivity reaching white at 90◦), but in the case of real metals this is not a
limitation: to our knowledge, the required edge tint is always less than or equal to 1. This could be considered
a benefit, as it makes it impossible to produce physically implausible metals with excessively bright edges
Figure 4: These renders of a sphere in a white furnace compare the original F82 model (left) and our F82-tint model
(right). The edge color is set to white in both cases. The original F82 model exhibits glowing edges that do not
conserve energy and would need to be clamped, while the F82-tint model produces a result identical to the standard
Schlick approximation to Fresnel. This means that a white edge color serves as an ideal, physically plausible default
value for the F82-tint model, essentially making edge tinting completely opt-in.
HAP|仲林 : THE ARTISTEER 