Stochastic flakes and Fresnel

[sharktacos]

I'm curious to understand how the examples for car paint and snow in the Stochastic paper could be replicated. The paper's PDF states that the car paint was made "with diffuse base layer, stochastic flakes middle layer, and reflective coat" and the snow similarly says it was made with a "sub-surface scattering base layer and stochastic flakes coat material"

From what I can see the stochastic material does not have Fresnel, but the car and snow both appear to have Fresnel on the flakes. One way to achieve this would be to connect a FresnelTex to the reflect filter and then use its "side color" to adjust the spec amount. Is this how these materials for car paint and snow were achieved? Or is there a preferred workflow for materials with Fresnel reflections?

The video further says the car paint used "GGX alpha 0.09 and gamma 0.3 degrees" while snow was "GGX alpha 0.25 and gamma 0.4 degrees." What slider values would correspond to these settings on the Stochastic material? For example I do not see a slider for GGX gamma (i.e. tail falloff) on the Stochastic material.

thanks

[asen.atanasov]

Hi,

the examples from the paper do not have Fresnel. They use the additive mode of the blend material. Currently, FresnelTex is the way to do it.

The parameter from the paper are mapped as follows:
blur angle = gamma
glossiness = 1 - sqrt(GGX alpha)
num flakes = sqrt(N)

Best regards,
Asen

[sharktacos]

Hi,

the examples from the paper do not have Fresnel. They use the additive mode of the blend material. Currently, FresnelTex is the way to do it.

The parameter from the paper are mapped as follows:
blur angle = gamma
glossiness = 1 - sqrt(GGX alpha)
num flakes = sqrt(N)

Best regards,
Asen

Got it, thanks.

As a follow-up question: I see that some work is being done on a Stochastic-Scratch material. There are basically two kinds of scratches
1) parallel scratches for things like brushed metal
2) cross-hatched scratches for things like an old spoon, or even the "spider web" specular one sees on microfacets of car paint (image below).
I'm curious if there are plans to make the Stochastic-Scratch material be able to accommodate both of these types of scratches, or even possibly work with texture maps (for example for circular patterns in brushed metal)?