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For details see the "Extending the Disney BRDF to a BSDF with Integrated Subsurface Scattering" paper. We split the diffuse BSDF into a lambertian and retro-reflection component. The retro-reflection component is always handled as a BSDF, while the lambertian component can be replaced by a BSSRDF. For the BSSRDF case, we compute Fresnel separately at the entry and exit points, which may have different normals. As the scattering radius decreases this converges to the BSDF case. A downside is that this increases noise for subsurface scattering in the Principled BSDF, due to some samples going to the retro-reflection component. However the previous logic (also in 2.93) was simple wrong, using a non-sensical view direction vector at the exit point. We use an importance sampling weight estimate for the retro-reflection to try to better balance samples between the BSDF and BSSRDF. Differential Revision: https://developer.blender.org/D12801
.. Keep this document short & concise, linking to external resources instead of including content in-line. See 'release/text/readme.html' for the end user read-me. Blender ======= Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline-modeling, rigging, animation, simulation, rendering, compositing, motion tracking and video editing. .. figure:: https://code.blender.org/wp-content/uploads/2018/12/springrg.jpg :scale: 50 % :align: center Project Pages ------------- - `Main Website <http://www.blender.org>`__ - `Reference Manual <https://docs.blender.org/manual/en/latest/index.html>`__ - `User Community <https://www.blender.org/community/>`__ Development ----------- - `Build Instructions <https://wiki.blender.org/wiki/Building_Blender>`__ - `Code Review & Bug Tracker <https://developer.blender.org>`__ - `Developer Forum <https://devtalk.blender.org>`__ - `Developer Documentation <https://wiki.blender.org>`__ License ------- Blender as a whole is licensed under the GNU General Public License, Version 3. Individual files may have a different, but compatible license. See `blender.org/about/license <https://www.blender.org/about/license>`__ for details.