Tuesday, November 9, 2010

SSS courtesy of Leslie

Quick Guide for setting up a an object with a basic Subsurface scattering shader

1. Create object(s)
Subsurface scattering is most visible on objects that have areas of thin geometry

2. Create two lights
1 area light: lighting the front of your object with an Intensity of ~ 1.2
1 spot light: lighting the back of your object with an Intensity of ~ 1.5

3. Add a misss_fast_skin_maya shader to the object(s).

a. In the Attributes Editor for the shader, change the following Weights down to
Diffuse Weight
Epidermal Scatter Weight
Subdermal Scatter Weight
Primary Specularity Weight
Secondary Specular Weight

b. Start by entering a value of 0.500 for the Back Scatter Weight.

c. Render the scene…and be sure your camera is facing the front of the object
(this allows the object to be backlit by the spotlight).

d. Adjust the Back Scatter Weight until you can see a notable red glow to the
out edge of the object. The Back Scatter Radius can be increased/decreased
determine the spread of the glow. ***If you are seeing a black screen with
NO red glow, see the Normals solution below.

e. Continue to add values to the different scatter weights, in this order:
Primary Specularity
Secondary Specularity

***Normals Solution
Problem: When you first drop the SSS shader onto an object and render it, it does
not look anything like subsurface scattering (looks like a regular blinn) OR when
you render with only a value in Subdermal Scatter Weight, you get a black screen
with no red glow.

1. Select the Object
2. From the Polygons Menu, choose Normals > Reverse
3. Render again, and you should now be able to see the subsurface scattering effect.

extra note:
to give the impression of an object within your main sss object that blocks some of the light coming through, put the same sss shader on the small blocking object and place it inside the geometry of the main object

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