Discuss: Maya SSS shader

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Discuss: Maya SSS shader

文章HapZungLam » 2日 9月 2009年, 08:11

I have been playing with the mentalray Miss_Skin_Maya shader for Maya for some time. This is what I found to setup realistic skin material. Im here to share my experience with you. I know that this is still under construction stage and I will improve it for better result. This is not the best and will always be a better way of doing it. If you have a different point of view or have anything add to it please feel free.

This tutorial is currently in English. I'll "try" to translate into Chinese when Im not lazy.

The character for this demonstration is Maurice. I did the base model and UV in Softimage, detailing in Zbrush, texture in Photoshop CS4(very nice with the new 3D mode) and finally back to Maya for rendering.
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文章HapZungLam » 2日 9月 2009年, 08:12

Understanding:

SSS is a combination of a several value: Overall, Diffuse, Epidermal, Subdermal, Back Scatter, Primary Specular and Secondary Specular

Think of a real human skin. We have our first layer of skin. Under there is a second layer of skin, then fat, then vain and muscles. Use that as an idea to apply onto each map. Overall as the overal value of all the maps. Diffuse will be your first and second layer of skin. Epidermal will be the fat layer. Subdermal will be the vein and muscles. Back Scatter is also the vein and muscles but it will only appears when the light shot from behind. Primary spec will be the major specular value of the skin under no oil or water on top. Secondary specular will be the oil on top of the skin.

I'll break it up individually with the map I created for further explaination.
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文章HapZungLam » 2日 9月 2009年, 08:12

Overall and Diffuse

Overall is like a colour which will overide all the maps as a multiplyer. Diffuse is just like a regular diffuse from a phong or a blinn. In this case, I hook up my diffuse map into the overall channel. However, I use the diffuse colour to control the brightness of the final result. I find it pretty good for my lighting setup. You may have to try it out both channel and see which channel fits your diffuse map better.
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文章HapZungLam » 2日 9月 2009年, 08:13

Overall map:
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文章HapZungLam » 2日 9月 2009年, 08:14

Overall map:
It'll appears too much detail if you hook up your diffuse map right into the overall channel. What I did is to brighen the diffuse map up a little bit and lower its contrast.
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文章HapZungLam » 2日 9月 2009年, 08:16

Diffuse map:
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SSS_Default.jpg
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文章HapZungLam » 2日 9月 2009年, 08:16

Diffuse map:
This is what the original texture of the head. I map it with photos in photoshop. In my case, I m not going to use this map for any of the channels.
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文章HapZungLam » 2日 9月 2009年, 08:17

Epidermal map:
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SSS_Epi.jpg
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文章HapZungLam » 2日 9月 2009年, 08:17

Epidermal map:
As I explain perviously to use epidermal as the fat layer of a skin. What is inside the middel layer of the skin should include in this map. eg: fat, different layers of veins, differnt thickness of fat, some fat may blend into some of your muscles, etc. The more detail you give to this map will get you better result.

In my map, I did not mono tone my diffuse map into yellow. Try to avoid having grey value. If you want to have some dark area, make it more saturate when you tone down the curve.
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文章HapZungLam » 2日 9月 2009年, 08:18

Subdermal map:
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文章HapZungLam » 2日 9月 2009年, 08:18

Subdermal map:
This is the muscles and bone layer. More or less is just pure red. I can add more variaty to it but I find it un-noticable. So I just use my diffuse map and monochromatic to red. This red map will appear on very outer each of your skin. You will not see anything under direct light.
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文章HapZungLam » 2日 9月 2009年, 08:19

Back Scatter map:
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文章HapZungLam » 2日 9月 2009年, 08:19

Back Scatter map:
This will only show up when a light his shining from behind. Notice that if you give too high value to this channel will make your object looks like wax. A lot of user feeling happy to crank this value up because they don't see the effect. But this should just be a little touch ups on the corner of the ear and nose in my opinion. Over done it will appears waxxy looking.

I dim it with Subdermal map and brighen up a bit around the corner of the ear and the tip of the nose where they have no bone structure to block the light.
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文章HapZungLam » 2日 9月 2009年, 08:20

Primary Specular:
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文章HapZungLam » 2日 9月 2009年, 08:21

Primary Specular:
Warning: Do not brighten your specular on skin ever. Notice that the skin is actually a pretty dull material. The little specular you see is almost react like regular diffuse. Even the lip should be not much different from any other places of the skin. People see specular on their lip either after they lick themselves or wearing lip gloss. Do not over done on the lip.

As you notice my specular map is really dark and having a little blue tone to it. You may make it pure de-saturate but I found a little blue will make it contrasts nicely with the skin.
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