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This Bxdf is based on Brent Burley's extended material model, introduced in "Extending the Disney BRDF to a BSDF with Integrated Subsurface Scattering" at SIGGRAPH 2015.
It The PxrDisneyBsdf is a nice and simple physically-based model with a concise number of parameters, allowing for a wide range of photoreal and artistic materials, including diffuse and specular reflection and transmission, clearcoat, sheen, and subsurface scattering.
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