Map creation questions for rendering skin

obloquy · May 2019

Hey, I've done a lot of research into map creation for rendering skin, but still have a few questions I wanted to ask to clarify.

Currently I've finished diffuse and displacement/bump maps based on xyz scans. I know that I need a gloss and a spec map which seem fairly straight forward to create in mari.

One of the things I'm stuck on is creating an sss map and an sss weight map. I've seen some artists who look like they've taken an AO map and overlayed it over a desaturated version of the diffuse map with hue changed in places to make an sss map - not sure if I'm right there (see pic1). But at the same time theres artists on the Marmoset toolbar tutorials & xyz pages where that use multiple sss maps for deep/mid/shallow scatter skin sss so not sure whats what and what the real difference is between these two methods are... it seems a bit of a grey area (see pic2) I'm rendering in Arnold 5 for maya 2018 and it seems that SSS layers have been removed on the aistandard shader and just limited to a single slot..

For the sss weight map (or is it called the sss mask like in pic 1?), am I right in saying that it can be created using a transmission/thickness map in SP or Toolbag. At the same time Şefki Ibrahim's work (see pic 3) shows the sss weight map in the bottom right hand corner that looks really blurry and with some procedural noise (?) added, so not sure what produces the best results now or if I'm on the right track. I thought that Knald seemed great for this but I don't think it supports udims at the mo

Also I wanted to utilise the skin pore details from the xyz scans in the spec map so that in the final render the pores/skin wrinkles don't look flat when the sss is applied and 'pop' more ... would creating a cavity map thats overlayed/multipled over the spec map be the best solution for this? Again I thought Knald would be the best approach for this but no udim support

Sorry for all the questions, just wanted to be certain before I start

Many thanks for whoever can help me

Pic1

Pic 2

Pic 3

Image: https://us.v-cdn.net/5021068/uploads/editor/2a/eqogbzt3x8am.jpg

musashidan · May 2019

If you're using Arnold 5 then there are is only a single map for the flesh. The shader soesn't use the 3-layer method. Arnold 4 used the ALsurface skin material which was a 3-layer setup, but the ALshaders won't be ported to Arnold 5.

The way the new A5 skin works is that a lot of your spec/rough detail comes from your microsurface bump map(displacement with autobump enabled)

Over the years there have been as many skin map setups as artists. Everyone does it a bit differently. Now though, the shader is doing a lot more of the work so creating all thee maps has been simplified(latest Arnold core is using randomwalk2.0 SSS)

Basically, you drop an albedo map(your painted skin/flesh tones) into both the base colour of the shader and into the subsurface colour. The SSS radius colour has the most effect on the final SSS look. In this shader you can essentially set this up with or without a map. You set a high Red value(around 1), a lower Green value(around .35), and a lower Blue value(around .2) because this is the order and strength that light penetrates the skin in reality. You can optionally add a map here for veins, etc, but this essentially replaces the 3-layer shader aproach because the SSS radius values are effecting the values on your albedo map, so you don't even need a deep scatter map becuase veins/etc can be painted directing into your albedo texture. Scale plays a big role and can have a drastic effect.

For the spec/rough you can just use breakup maps. The microsurface dispalcement will take care of most of this. Some of the older skin shading methods relied on primary and secondary spec layers, but again, this isn't the case in Arnold 5.

Have you studied the Emily project?(and the newer one by the same group) There are some great examples of real-world spec values captured under lighting conditions that allow us to see the spec exactly as we see it in a black shader.

obloquy · May 2019

Ahh right I see now, I knew that you need to drop the albedo into the sss and base but kept seeing a lot of variations with the maps specifically the sss weight and what not so wasn't too sure. I'm aiming for more of 'stylized realistic' look with sort of a 'heavy' sss sort of similar to like what Guzz Soares, Matias Zadicoff & Pedro Conti do (pics below). I wanted to maybe use vray as its something I've wanted to learn along with the al surface shader/fastsss it has as the results looks great for a stylized look.

I read up on the older emily project but didn't know there was a newer one so will defiantly check it out. Thank you again for answering my (annoying) musashidan, was very helpful and cleared up a lot of questions!

Map creation questions for rendering skin

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