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What in the World is a BSDF? - CGC Weekly #16


pavla writes:

The letters "BSDF" are scattered everywhere throughout the world of computer graphics, but what does it mean?! We'll investigate the definition and uses of this elusive CG vocab word in this week's episode of CGC Weekly.


  1. Tishard Nathaniel on

    But if the sub-surface scattering shader is in the principal shade does that mean it's a bsdf now?

    • Well, yes and no. I guess that depends on how strictly you define BSDF. If you see it as the subsumption of BRDF and BTDF (which deal with the scattering of light at the incoming and the outgoing surface, without regard of the volume), than no.

      If you use BSDF as a subsumption for all bidirectional distribution functions, then BSSRDF (which describes the subsurface scattering) has to be considered a BSDF as well. The BRDF is a simplified BSSRDF, too - assuming the depth to be zero (or infinitesimal?), so a BSSRDF is contained within the BSDF.

      Since in Blender the Volume shaders have no BSDF in their name, it looks like it's strictly the BRDF and BTDF they refer to. And after all, the Principled BSDF may have subsurface scattering as an option, but most of the settings are for reflectance and transmittance.

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