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Greg Hughes avatar image
Greg Hughes asked ·

How to create a subdermal map for SSS?

I believe there is a way of using a "subdermal map" with the Subsurface parameter of the aiStandardSurface shader so you can target what areas of a mesh show more of the chosen subsurface colour, e.g to target ears on a mesh of a human head with SSS so they appear more red on the inside. If you just use the skin shader preset as is, the ears look light pink, like a plastic doll.

Is the subdermal map meant to be a greyscale texture? And where exactly do you plug it in -- Radius?

I am assuming you would manually paint on the map in a program like Substance Painter and export it to Maya. Any one have any experience with this, or a tutorial?

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Lee Griggs avatar image
Lee Griggs answered ·

Here is an example with an SSS radius map connected to radius (without and with comparison renders 2nd from right).

>Can you just paint in greyscale and set a red colour for the >Radius swatch in the aiStandardSurface shader to tint it?

The image on the far right is the result of that.


radius.jpg (94.5 KiB)
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Lee Griggs avatar image
Lee Griggs answered ·

Yes, a red map to radius.

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Greg Hughes answered ·

@Lee Griggs

Hello Lee,

If you use a red coloured map, can you make some areas more affected, like the ears, by painting on a certain shade of red? e.g. would you paint more saturated red to make it show more on the ears than on the face? WOuld that be how it works?

Can you just paint in greyscale and set a red colour for the Radius swatch in the aiStandardSurface shader to tint it?

Thanks

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Greg Hughes answered ·

@Lee Griggs

Thanks Lee!

For the second example image with the red ears, did you just change the Subsurface Color parameter from skin pink to a red colour? Presumably the first example with the pink/tan ear used the pink/tan skin colour as shown in the image of the parameters?

Would you know if you have to manually paint the greyscale map or is there a simple method for generating them, perhaps in Substance Painter with an occlusion map or something?

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Lee Griggs avatar image
Lee Griggs answered ·

>For the second example image with the red ears, did you just change the Subsurface Color parameter from skin pink

Its the same map but colorized red.

>simple method for generating them, perhaps in Substance Painter with an occlusion map or something?

Maybe you could bake an AO shader using Render Selection to Texture.

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Greg Hughes answered ·

Thanks Lee, I will look in to Render Selection to Texture.

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Greg Hughes answered ·

@Lee Griggs

I was also wondering... would you output the rendered image of the red ears shown as a separate compositing layer to blend with the diffuse map pass? If I use a red tinted greyscale map the blacks appear in the image, overriding the Base Color. I had assumed black would be ignored by SSS and simply not show through -- it seems I was wrong.

So presumably the map must be a mix of the diffuse skin color (tan/pink) and red (ears) to make the SSS blend correctly in a single render within Maya? Perhaps you need to just paint a red tint in the ear on the diffuse map and use this for SSS Radius?

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Greg Hughes answered ·

@Lee Griggs

My further research (Arvid Shcnieder's tutorial on skin shading) indicates that the way to do this properly is to add the diffuse map to the Subsurface Color, not the Radius, and set the Radius parameters to make the red light scatter more deeply.

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Lee Griggs answered ·

JFYI, here is a recent test of the Emily scene and it looks fine without needing to connect a map to the SSS Radius.


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Greg Hughes answered ·

@Lee Griggs

Hello Lee,

That seems to be the way to do it. The Radius parameter is more for controlling the scattering of the RGB channels, e.g. deeper penetration by red light for skin, as well as setting the appropriate scale for the scattering to work effectively on a mesh of a particular size or thickness in certain areas like ears. At least that is what my research indicates. I think you would set the Radius colour to a red shade to get more obvious reddening of the ears.

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