I set this layer to Screen mode; this way I got all the detail of the bump going through the white zones I'd just painted. Now, playing with the opacity of the white layer, I was able to adjust the level of specularity. I also added a tuning layer between the bump and displace group and the "white zones" layer, to adjust the luminosity of the details, in order to obtain this for my final specular map (Fig.23).
Of course, all these maps needed tweaking once I started test rendering the picture. I could have done a simple specularity map, with just black and white areas, without using the bump map as a background, but using this bump map helped to get better details during the rendering. It sort of underlined the bump, as if skin pores and wrinkles didn't have as much specularity as the rest of the skin, which is probably right in real life too.
On this project, I wanted to test the new mental ray sss2 shader. It basically works the same way as the former version, but has some new tools, that are definitely worth a look. You can now play with a 3 color tuner (red, green and blue) for the radius of each level (epidermal, subdermal, backsurface etc), You can also use two layers for reflections and two others for specularity, and the results are way better than the former shader.
So, how did I get started? First of all, I set up a simple scene. Then I imported my basemesh, applied a Turbosmooth modifier to it, with enough render iterations to get my sculpting details, then added a Displace modifier and plugged the displacement map into the map slot (Fig.24).
Your displacement map needs to be at least a 16-bit image or you'll get poor results. I worked with a 32-bit EXR map, which are very convenient when using displace. I just put the displace strength to 1.0 and there was no need to spend hours making adjustment (Fig.24).
Next I applied the sss2 material to it, and plugged my normal bump into the bump map channel (Fig.25).