Subsurface Scatter Question

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sldstt

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May 13, 2023, 1:48:40 PM5/13/23
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Hi, I'm playing around with a subsurface scatter, but seems like I'm missing something.

My scene is just a flat subsurface material wall with no texture. the only light source is a spot light which produces a small spot on the wall. My expectation was that with enough samples I should be able to reconstruct the diffusion profile for this material, but no matter what parameters I'm using (mean free path and reflectance), I get the same result, just a few lit pixels and that's it.

What am I doing wrong here?

Thanks

Matt Pharr

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Jun 9, 2023, 7:52:44 PM6/9/23
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Can you post the scene?

Thanks,
Matt

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sldstt

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Jun 11, 2023, 4:31:59 PM6/11/23
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Sure, here it is. I took the mfp values from the "head" scene for no particular reason. 
I'm illuminating the wall with a small spot, but changing these parameters doesn't seem to have any effect.

Thanks

LookAt 0 0 0
0 0 1
0 1 0

Camera "perspective"
"float fov" [1]

Sampler "halton" "integer pixelsamples" 256
Integrator "volpath"

Film "rgb" "string filename" "wall_ss.exr"
"integer xresolution" [200] "integer yresolution" [200]

WorldBegin

LightSource "spot"
"rgb I" [1 1 1 ]
"float coneangle" [0.03]
"float conedeltaangle" [.01]
"point3 from" [0 0 0]
"point3 to" [0 0 1]

AttributeBegin
Material "subsurface"
"bool remaproughness" [ false ]
"float vroughness" [ 0.01 ]
"float uroughness" [ 0.01 ]
"float eta" [ 1.33 ]
"rgb reflectance" [0.2 0.2 0.2]
"rgb mfp" [ 0.0012953 0.00095238 0.00067114 ]
Shape "disk"
"float height" [.001]
"float radius" [100]
AttributeEnd


sldstt

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Jul 11, 2023, 8:30:07 AM7/11/23
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update: looks like using "skin1" or "skin2" I can get some visible SSS effects. Am I setting the mfp/reflectance paramters wrong?
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