painting sss maps for external rendering

[system]

I wasn’t exactly sure which part of the forums I should ask this on and I hope I’ve hit the right place.

I’ve been using zbrush to polypaint different maps for mental rays skin sss shader. I’m wondering whats the best way to do this:

1. Should I paint the subdermal, export that, then start from scratch and paint a bloodless pale white epidermal and export that as a second map?

2. Paint normal skin colors, with freckles and everything then export that as a single map and desaturate/saturate it for the epidermal and subdermal respectively in photoshop or other similar programs?

3. Some other way?

I’m rendering in 3dsm with mental ray as previously noted. I’ve done a lot of tests but my results are always terrible so I’m looking for some tips or points to the right direction.

Thanks.

[Trist]

Gday,

There’s a great Sybex book by Scott Spencer called “Zbrush Digital Sculpting - Human Anatomy” that has a section on SSS, for mental ray in apps such as Max.

There are pages of info on the subject but to put you in the right direction (always remeber techniques vary depending on the current work):

First of all paint in your Back Scatter map - an anatomical reference will help you see where to paint the muscle and bone (check out www.3D.sk for refs)

For the subdermal layer you can actually use the back scatter as a base. Give it a coat with a light pink colour and you can go from there with the rest of the detail you need.

Assuming you have a good understanding of what should go into the two previous layers, start on the Epidermal. As you have probably gathered by now, this is the top layer of skin where you will find moles and freckles etc and the overall skin shade.

As for the translation into Max, you will of course have to export out the layers separately as maps and then insert each one in its respective channel in a mental ray SSS shader. There are other enhancements you can add to your effect such as specular and bump.

It may take some time to perfect the skin in Max, google the subject and you will find some basic tutorials on the easiest way to get a good effect.

So there’s a REALLY simplified explanation that should give you a starting pont.

Good luck!

[system]

Thank you Trist, especially for the book. However I have a few more questions regarding your post:

In mental ray, isn’t the subdermal more important than the “backscatter (through)” slot since the backscatter will only be visible in certain light?

Shouldn’t the subdermal be highly saturated red/orange with maybe purple capillaries and a little yellowish fat rather than light pink, basically like a skinned face?

The epidermal should be basically like blood drained skin, lightly pink and blueish. Combined they should give out something more naturally skin colored or am I way off?

I’m not looking for 3dsm tutorials or mental ray, but more trying to wrap my head around how the maps multiply each other and what colors work best together.

Thanks again.

[Trist]

Unfortunately there is no set answer to your question. Depending on the particular effect you desire, you will need to tweak values such as the “weight”" of the channels relative to each other until you find a good balance. For example, if you wanted a strong effect of a red tinge through the ear and nose, you would give the back scatter more weight.

You are more or less correct about the subdermal containing capillaries etc. What I meant is that you can use the back surface (through) with a pink coat as a base. And yes, it can be highly saturated with reds etc. Remember you will need to paint several passes until you get an effective result (but this goes with pretty much any texturing you do).

With the epidermal layer, how it looks will obviously depend on the ethnicity of the character. Here you will find dark blue around the bearded areas (if male) and reds around the nose and eyes, pale purple around the lips etc. Then all of the surface stuff like freckles and moles. Also with the epidermal it’s a good idea to break up the colours to suggest the natural imperfections found on skin (unless you are aiming for a clean, cartoony look).

All of that said, there are general rules but they can be stretched and some can be broken.

I have really only touched on the subject here, this thread could go on for some time before all of the known techniques were explained and I’m still learning myself.

I hope I can help you with any other questions but the best bit of advice I can give you is to not get too bogged down in the technical details and have some fun with your artwork and just experiment with the effect.

And by all means, check out the book I mentioned before - It’s one of the best I have found!

I will probably write a tutorial on the ZB SSS to Max workflow when I have it all figured out. Please feel free to share any tips you might learn from your experience.

Cheers!

[system]

Thanks again Trist, very helpful. The book looks very interesting from what I’ve seen and I’ll be checking it out. I’m sure a lot of my questions will be answered by reading it.

As for sharing tips, I’m sure my knowledge is still way too limited on the subject. But I will be keeping an eye open for your tutorial as well as other similar topics where my limited knowledge might perhaps help one day.

[Trist]

No worries. Good luck!