# Subsurface scattering field

I have color A and color B and you want sub surface scattering. My question is, on the "thickness" map, does pure white represent complete translucency or does grey?

White would mean I'm taking 100% of color B right? Which means color A will not be present at all which isn't translucent. So my guess is .50 (grey) is the true value if you want both colors? Or am I wrong?

I already tried this with principle shader with red and blue creating purple with .5 (grey) sub surface scattering:

If I have white, I would be taking 100% of color B, thus there is no translucency with the red.

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So my basic question is, when I make a sub surface scattering map, should I be using grey for max translucency? Or is there something I'm missing here? Because I have seen White areas in thickness maps before which makes no sense to me, you're just taking 100% of color B?

• Hello :). The slider doesn't simply mix the two colors. It works as a multiplier for the Subsurface Radius values. So having it at 1 often makes sense. Blender Manual - Principled BSDF Commented May 17, 2020 at 18:43
• Thanks the math makes sense but I don't understand why color A would vanish completely when set to max... If they colors simply don't "mix", wouldn't I see some traces of the red? Commented May 17, 2020 at 19:40
• Hello :). This is a special case where you're using pure RGB Blue so only blue channel is available. See my answer. Commented May 17, 2020 at 23:08

When Subsurface is 1, the Base color has no influence.
Still you can use radius to extract different colors from the Subsurface color.

Why it doesn't work for you
You're using RGB Blue (0,0,1), so Red and Green cannot be extracted (as they're zero).

Example
I'm using some random Blue containing all three channels (RGB: 0.14, 0.19, 0.8):

• Subsurface = 1 (so the base color has zero influence)
• I can bring up plenty of Red from my Blue, using the Subsurface Radius.

• Thanks Jachym, what value would be recommended for skin? Probably not 1.. Commented May 18, 2020 at 0:26
• Hello :). This thread could help: Principled BSDF subsurface scattering values for skin material. Also the Subsurface Radius will be rather important. Commented May 18, 2020 at 9:48