asPlastic¶

A physically correct plastic shader, stacking a specular term on top of a diffuse substrate.

Parameters¶

Diffuse Parameters¶

Diffuse Color: The diffuse color.
Diffuse Weight: A scaling factor for the diffuse BRDF.
Scattering: The scattering amount for the diffuse term. Full scattering will take into account all the events in the specular term, while a value of 0 will disable them.

Specular Parameters¶

Specular Color: The specular color.
Specular Weight: A scaling factor for the specular BRDF.
Index of Refraction: The index of refraction for the (dielectric [1]) Fresnel term.
Specular Roughness: The apparent surface roughness, with a value near 0 producing sharp highlights, and a value of 1.0 producing soft diffuse like highlights.

Note

As specular roughness values increase, there is energy loss due to the lack of multiple scattering [Heitz:2016:MMB:2897824.2925943]. Appleseed however does compensate for this energy loss.

Bump Parameters¶

Bump Normal: The unit length world space normal of the bumped surface.

Matte Opacity Parameters¶

Enable Matte Opacity: Parameter that toggles matte holdouts.
Matte Opacity: Matte opacity scaling factor.
Matte Opacity Color: Holdout color.

Advanced Parameters¶

Ray Depth: The maximum ray depth a ray is allowed to bounce before being terminated.

Outputs¶

Output Color: The plastic BRDF output color.
Output Matte Opacity: The matte holdout.

Screenshots¶

Footnotes

[1]

Dielectric is a material which is an electric insulator, the opposite of conductors which as the name says, conducts electricity. See this page on dielectric materials for more details. In terms of look development an accepted simplification is that dielectrics have white or non-tinted specular highlights, while conductors have tinted or coloured specular highlights.

[2]	The microfacet distribution function is a function that describes statistically the microscopic shape of the surface’s as a distribution of microfacet orientations. See the this page on the normal distribution function (NDF), and this page on specular highlights for more details.

References

[HHdEonD16]

Eric Heitz, Johannes Hanika, Eugene d’Eon, and Carsten Dachsbacher. Multiple-scattering microfacet bsdfs with the smith model. ACM Trans. Graph., 35(4):58:1–58:14, jul 2016. URL: http://doi.acm.org/10.1145/2897824.2925943, doi:10.1145/2897824.2925943.