Apart for taking ages to come up with a title for this segment that rhymes it seems that throughout my time messing about with 3D/2D stuff I may have picked up a few things from trial and error that others might have missed! So to save everyone the pain and agony that I went though I decided to start a series of posts detailing how I have managed to achieve some of the visuals in my pieces over the years – as such without further ado let’s jump into the topic of skin!
I will mostly focus on the human face for this part, but some of these should definitely be useful for recreating human skin and texturing in general.
For this image I used:
> a basic default female face available as a Subtool in Zbrush as a base
> bump maps from texturing.xyz
> MARI – for texturing
> Zbrush – for sculpting
> Photoshop – for texture adjustments (MARI tends to melt my laptop if I get too wacky)
> Keyshot for rendering
When it comes to texturing the human face there are three main maps that we will look at – Bump Maps, Specular Maps and Diffuse Maps.
This particular model was initially textured with displacement maps that were downloaded from texturing.xyz. One of the first things you might notice with the original files from the website is that they come in 3 different detail levels. This is important as in the long run it will give us great control over skin roughness and pore details. At this stage in order to maximize the texture detail I decided to use MARI to texture my model.
Using MARI however did require some preparation on the texture files. For example the highest texture size that MARI supports on its pain buffer is currently 16k. This meant that the original files had to be cut into smaller pieces in order to work with the software.
Another technical formality was that I needed to be able to paint with 3 different textures at the same time. To do this I assigned all 3 original textures to a single color channel (as they are greyscale diffuse maps) secondary detail was given the red channel, tertiary the blue and micro details the green – this separation meant that I could later again extract separate displacement values from a single color image. The pieces were then imported into MARI and projected onto the mesh.
*an excellent tutorial for the previous paragraph can be found here.
Once I had the model fully textured I took the UVs into Photoshop and separated them into individual greyscale images again. At this point I moved onto Zbrush where I would actually apply my displacement maps. This was done because Zbrush is currently the fastest way I can think of seeing how a displacement map will work on a model with up to 20 million polygons in real time. I work with an extremely high poly model as my workflow also relies on Keyshot for rendering which does not process displacement maps in a realistic manner when it comes to organic models.
Once in Zbrush I imported my Secondary detail map and used the “Mask by Alpha” function. I then used the “Move” brush it manually push and pull masked sections of the skin – this allowed me to control pore depth and skin smoothness in individual areas of the face. Once I was happy with the result the same process was repeated with the other two maps.
The next step was to create a Specular Map – this would dictate which section of the skin would reflect more light and accommodate for build up of sweat, oil or dry skin.
To create these I used a blend between the displacement maps as a base (where light areas would indicate more gloss and the dark less gloss) – for Specular detail on a pore level. I next Polypainted the model in Zbrush highlighting the areas like the lips and the eye lids as well as some parts of the cheeks and forehead where more gloss is needed.
Finally it was time for the Diffuse or Color Maps. To start off I used a photo with the “Eye-Drop” tool in Zbrush to extract some skin colors. Next I used the “Mask by Cavity”, “Mask by Smoothness” and “Mask by Alpha” functions to color the face in separate sections while keeping and expressing some of the displacement detail in the color map with thinks like dirt and dry skin. While this game me great results I decided to export this color map to Photoshop where I overplayed and blended some of my original displacement maps on top to bring back that full 16k resolution of detail to my color map. The final touches were to fade out some of the pore detail through make up and skin irregularities.
When it came to the final render we now have all the essential maps we need for a believable face. I also experimented with converting some of my Displacement Maps to Normal Maps and in some lighting conditions in Keyshot this produced superior results, however due to the nature of the project at the time I decided to use Displacement Maps as they expressed the Specular Maps better.
*Displacement vs Normal respectively
Some of this things I did not explore in this section are Roughness Maps (long story short – inverted Speculer Maps) which Keyshot supports in their more advanced materials. This is because at the time there is a bug with the advanced translucent material that prevents a Roughness and a Color Map to show at the same time – this could potentially give great visuals in the future.
Another texture map that I didn’t mention is the Subdermal Map – This is used in a translucency material where different sections need to transmit different colors. While this is the most realistic method for rendering skin – I found that these maps have little to no visible impact on model appearance at the expense of massive render times. Should you wish to pursue them though (hopefully in different renderer) they are achieved by increasing the saturation and redness of the color map (it usually worth adding blue patches around the eyes where the skin is thinner – hence visible veins)
*Rough idea of a Subdermal Map
In the end of the day with some tweaking of the maps contrasts and brightness within Keyshot you should be able to get a result similar to this.