[Bf-docboard-svn] bf-manual: [8453] trunk/blender_docs/manual/render/shader_nodes/shader: Update SSS documentation for Cycles-X changes

[Alaska]

Revision: 8453
          https://developer.blender.org/rBM8453
Author:   Alaska
Date:     2021-10-06 03:43:53 +0200 (Wed, 06 Oct 2021)
Log Message:
-----------
Update SSS documentation for Cycles-X changes

Differential Revision: https://developer.blender.org/D12608

Modified Paths:
--------------
    trunk/blender_docs/manual/render/shader_nodes/shader/principled.rst
    trunk/blender_docs/manual/render/shader_nodes/shader/sss.rst

Modified: trunk/blender_docs/manual/render/shader_nodes/shader/principled.rst
===================================================================
--- trunk/blender_docs/manual/render/shader_nodes/shader/principled.rst	2021-10-06 01:17:53 UTC (rev 8452)
+++ trunk/blender_docs/manual/render/shader_nodes/shader/principled.rst	2021-10-06 01:43:53 UTC (rev 8453)
@@ -45,6 +45,10 @@
    The X, Y and Z values are mapped to the R, G and B values, respectively.
 Subsurface Color
    Subsurface scattering base color.
+Subsurface IOR :guilabel:`Cycles Only`
+   Index of refraction for *Subsurface Scattering*.
+Subsurface Anisotropy :guilabel:`Cycles Only`
+   Controls the directionality of subsurface scattering.
 Metallic
    Blends between a non-metallic and metallic material model.
    A value of 1.0 gives a fully specular reflection tinted with the base color,
@@ -139,17 +143,20 @@
 
 Subsurface Method
    Rendering method to simulate subsurface scattering.
+   
+   .. note:: Eevee does not use these subsurface scatter methods but instead uses an approximation.
 
-   :Christensen-Burley:
-      Is an approximation to physically-based volume scattering.
-      Gives less blurry results than Cubic and Gaussian functions.
-   :Random Walk:
-      Provides the most accurate results for thin and curved objects.
-      This comes at the cost of increased render time or noise for more dense media like skin,
-      but also better geometry detail preservation.
+   :Random Walk (Fixed Radius):
+      Provides accurate results for thin and curved objects.
       Random Walk uses true volumetric scattering inside the mesh,
       which means that it works best for closed meshes.
       Overlapping faces and holes in the mesh can cause problems.
+   :Random Walk:
+      Behaves similarly to *Random Walk (Fixed Radius)* but modulates 
+      the *Subsurface Radius* based on the *Color*,
+      *Subsurface Anisotropy*, and *Subsurface IOR*. This method
+      thereby attempts to retain greater surface detail and color than
+      *Random Walk (Fixed Radius)*.
 
 
 Outputs

Modified: trunk/blender_docs/manual/render/shader_nodes/shader/sss.rst
===================================================================
--- trunk/blender_docs/manual/render/shader_nodes/shader/sss.rst	2021-10-06 01:17:53 UTC (rev 8452)
+++ trunk/blender_docs/manual/render/shader_nodes/shader/sss.rst	2021-10-06 01:43:53 UTC (rev 8453)
@@ -32,48 +32,32 @@
    The scattering distance is specified separately for the RGB channels,
    to render materials such as skin where red light scatters deeper.
    The X, Y and Z values are mapped to the R, G and B values, respectively.
-Sharpness
-   Used only with *Cubic* falloff.
-   Values increasing from 0 to 1 prevents softening of sharp edges and reduces unwanted darkening.
+IOR :guilabel:`Cycles Only`
+   Index of refraction for *Subsurface Scattering*.
+Anisotropy :guilabel:`Cycles Only`
+   Controls the directionality of subsurface scattering.
 Normal
    Normal used for shading; if nothing is connected the default shading normal is used.
-Texture Blur
-   How much of the texture will be blurred along with the lighting,
-   mixing the texture at the incoming and outgoing points on the surface.
-   Note that the right choice depends on the texture.
-   Consider for example a texture created from a photograph of skin,
-   in this case the colors will already be pre-blurred and texture blur could be set to 0.
-   Even for hand-painted textures, no blurring or minimal blurring might be appropriate,
-   as a texture artist would likely paint in softening already.
-   One would usually not even know what an unblurred skin texture looks like; we always see it blurred.
-   For a procedural texture on the other hand this option would likely have a higher value.
 
 
 Properties
 ==========
 
-Falloff
+Subsurface Method
    Rendering method to simulate subsurface scattering.
 
-   :Cubic:
-      Is a sharp falloff useful for many simple materials. The function is :math:`(radius - x)^3`.
-   :Gaussian:
-      Gives a smoother falloff following a normal distribution,
-      which is particularly useful for more advanced materials that use measured
-      data that was fitted to one or more such Gaussian functions.
-      The function is :math:`e^{-8x^2/ radius^2}`,
-      such that the radius roughly matches the maximum falloff distance.
-      To match a given measured variance *v*, set :math:`radius = sqrt(16 × v)`.
-   :Christensen-Burley:
-      Is an approximation to physically-based volume scattering.
-      Gives less blurry results than Cubic and Gaussian functions.
-   :Random Walk: :guilabel:`Cycles Only`
-      Provides the most accurate results for thin and curved objects.
-      This comes at the cost of increased render time or noise for more dense media like skin,
-      but also better geometry detail preservation.
+   .. note:: Eevee does use not these subsurface scatter methods but instead uses an approximation.
+
+   :Random Walk (Fixed Radius):
+      Provides accurate results for thin and curved objects.
       Random Walk uses true volumetric scattering inside the mesh,
       which means that it works best for closed meshes.
       Overlapping faces and holes in the mesh can cause problems.
+   :Random Walk:
+      Behaves similarly to *Random Walk (Fixed Radius)* but modulates 
+      the *Radius* based on the *Color*, *Anisotropy*, and *IOR*. 
+      This method thereby attempts to retain greater surface detail and
+      color than *Random Walk (Fixed Radius)*.
 
 
 Outputs