Sculpting and Polypainting 'The Cannibal'
Ivan de Andres Gonzalez takes us through how he used the tools in ZBrush to create his popular image, The Cannibal
In this tutorial, I will focus on my use of ZBrush techniques. You will see any number of useful processes within this software, including sculpting, Polypainting and using references; using Spotlight and working with paint brushes, alphas and strokes to achieve a realistic result.
To begin, references are essential to achieve your goal. You can look for real world references or artistic interpretations – both will help you to understand shapes and see what elements make an object unique.
I usually categorize the references in 3 groups:
Look for images that resemble what you want to achieve. These don't have to be exact references but they have to have similar appeal. My likeness references for this project were Julian Beck, Emperor Palpatine and 30 Days of Night.
This time you want more concrete images – you are looking for specific help. Maybe you need references for the smile, the eyes or the wrinkles. Try to find the same subject (the mouth, for example) from different angles and with different lighting. My detail references for this project included this old man.
3. Fine detail
Other artists' work and scanned material are your best bet for the fine detail. You want to know how it really is and how other people have interpreted them.
The references will accompany you during the entire process and will be your best guide, so invest all the time you can in collecting the best ones you can find.
Favorite sculpt brushes
There is no secret weapon here. For human sculpting, the DamStandard brush is a great tool, and you can combine it with the Inflate brush to give a more organic feel to the wrinkles. Clay brush is great to give irregularities to the skin and to achieve the look of fat beneath the flesh. To achieve the opposite, the hPolish brush is great – it lets you give tension to the skin. And the last one is the Move brush which will help you to shape the face and break straight lines.
These brushes are essential to sculpt pores. Not many people seem to know of them or utilize them, but they make your alphas work just right.
Nose pores are very different from cheek pores. Working with the 3 smoothing brushes, you can create these 2 different pores just using one generic alpha – simply alternate between peaks and valleys.
1. The Smooth Standard brush smoothes the entire surface equally.
2. The Smooth Peaks brush smoothes ONLY the peaks (the top), which lets you simulate an open pore as found on the nose.
3. The Smooth Valleys brush smoothes ONLY the valleys (the bottom) and lets you simulate a pimple.
Try them and you'll be amazed. In fact, it's a good idea to customize your ZBrush interface and keep them handy.
Detail alphas and strokes
This is where the fun starts! I added an overall layer of generic pores over the surface of the skin. Not very intense, but still covering the entire object. I used the Standard brush with Spray stroke and a generic pore alpha. I then added some more detail with the same generic pore, but changed the scale and orientation. I also used the Standard brush with the Drag stroke, then changed the alpha settings to achieve more diversity.
Then it was time for the smoothing brushes! I played with the different smoothing brushes to get some diversity.
I then introduced new alphas. These alphas had to be area dependant – with different alphas for different areas of the face. I tried to imitate the pore diversity of a real face using the Drag stroke.
Finally, I checked my work with different materials, lights and angles of vision. I don't use MatCap materials while I am sculpting, only for checking.
As you can see I love the Drag stroke – it's one of my favorites for detailing, and I miss this stroke a lot when I am painting in other software. You have a lot of control with this one.
Sculpting The Cannibal
One thing you have to be aware of is that the intensity of the fine detail is dependent on what type of work are you doing. For rendering, as was my case, the subsurface materials will smooth a lot of the intensity of the pores, so you have to exaggerate them a bit more in ZBrush. This is trial and error at first.
If you are going to render your model with subsurface shaders, you should put all your work into layers to have more control over the intensity. In fact, it's always a good idea to put your fine sculpt in layers. If you do that, you'll find that ZBrush smoothes all the visible content independently of what layer it's in. So you might have to hide and unhide layers from time to time.
What I tried to achieve with the cannibal's face was to make it very organic and with a lot of movement. I tried to break all the straight and parallel lines and all the patterns that you recognize as unnatural. I used the Move, Blob or Elastic brushes. I can also fix some of these later in Photoshop with Liquify too. The only pattern I kept was the straight line of the teeth because I wanted the viewers to recall shark teeth. They have very straight gums.
How to author your own alphas
You have to try this. There's nothing better than to use your own alphas to really accentuate your skills (and to not depend on other's work).
The process is very easy:
1. Choose an image you like. It has to have clean detail, and it's best to make it square.
2. Make it 16 bits. In Photoshop go to Image > Mode > 16 bits. Do this before doing any modification to the content of the image.
3. Convert it to black and white. I usually like the Blue Filter preset.
4. Add a High Pass Filter with a radius of 7, although this is content dependant.
5. Invert it.
6. Adjust the levels to leave only the detail you want.
7. Save it as a 16-bit PNG file.
The first thing you need is an idea of the color palette you want to use. What kind of skin tone and mood are you trying to achieve? Once you have your ideas clear, the best thing is to find a photo closest to your ideal palette and eliminate all the information that you don't need.
In my case, I only wanted to build a color palette with the color variation of a face. You can blur your reference to eliminate all the small details that can distract you. Photoshop's Surface Blur filter works well here.
ZBrush Spotlight is a good way to use your new palette. Just load your texture in ZBrush, add it to Spotlight and turn it on. Once you have the texture loaded into Spotlight you can follow these steps:
1. Shift+Z to unhide Spotlight.
2. Press Z to make it active for the Color Picker.
3. Hold C while you pick a color.
4. Shift+Z to hide Spotlight.
6. Repeat 1 to 5.
Favorite brushes, strokes and alphas for Polypaint
For Polypaint you only need the Standard brush – the fun is in the strokes and alphas. I used the Color Spray stroke to paint the first layer and the Drag stroke to add detail.
The alphas are the real weapon here. I used some of the ZBrush stock alphas like the veins and alpha number 08, but the real fun is in making your own.
You can spend any amount of time you want in choosing good photos and making your alphas, but in my case my alphas are nothing fancy. They work for the cannibal but if in the future I make a more subtle face, I will definitely redo them.
As always, talking about references is really important. There are a lot of free samples of scanned faces on the web – just pick a few and study them. You will find that the skin has a lot of detail and color variations. This richness is what you want to replicate in your texture.
Scanned references are great because they are just like an albedo map. They do not have shading information that can cheat you. With them you don't see speculars or shadow, just the color. So surf the web and start your own collection of scanned material. They are invaluable.
They are useful too, for thinking about new alphas. If you pay attention to the small details you can recognize groups of spots that you can isolate into new alphas and use later on.
Now you want a material that shows your albedo as you are painting it, that is, without adding any interference besides the reaction to the light sources. The Skin Shade Standard material is great for this. It's better that you check your progress from time to time with the flat color material. With the flat color material, you see your work as it is without any other information (no light, no specular). It's easy to lose a lot of time playing with different flattering materials so the best thing is to attach yourself to an unflattering one.
MatCap materials are not welcome here.
Look at your color palette reference (remember, the blurred one) and start to pick colors. You want to imitate the tonal variations of a real person, such as some gray in the beard zone or some blue below the eyes. We are not only pink; the human face has a lot of colors. Don't be afraid of colors – the trick is in the subtleness.
We are not adding detail at this time, only painting color areas with soft transitions between them. You will only need your Standard brush with no alpha and the Color Spray stroke with a color variance of 0,125 or less. The color variance parameter is great to achieve natural variety, but if you put a high number in, things start going crazy pretty fast! Pick a color and paint, pick a color and paint – easy!
Blend and detail
My favorite step! Here your scanned references are essential. I always do this with the Drag stroke – it can be slower but you have all the control. What you want to do now is to break the softness that we painted in the last step, adding detail to the soft transitions and more specific details.
To make the first point possible, it is better that you choose a somewhat generic alpha with generic round pores (Alpha 08 works fine here too) and start to drag them between the color islands. You can rotate and scale them while you drag them over your model, and vary their color to match how the skin looks in your reference. To accomplish the second point, the ZBrush veins alpha works great. It helps you to add little veins and more specific detail. You can vary the color and the softness of the alpha.
This is the time to use your entire arsenal – you're finishing your work and want it to be perfect. Introduce new alphas, vary the blur, contrast and mid-value parameters that you can find in the alphas shelf.
Your goal now is to achieve variety and subtleness. Check your scanned reference all the time. Play with the RGB intensity and the alpha blur. This always works: less RGB intensity is equal to more alpha blur. This way you can add depth to your texture by painting detail beneath the skin; for example, painting a deep vein or a broken superficial vein.
Skin shade standard
Always check your work by swapping between materials and light directions. You want to know what you are doing at all times, and for this you need to test your work under different conditions. The specularity of the Skin Shade material and the shadow of the light can give you some clues about how your texture is going to perform in later steps.
Polypainting The Cannibal
This is the most fun part and ZBrush really excels at it. I love how clean you can visualize your work, how easy you can change your light, the great strokes you have at your disposal and how great the alphas work. I miss a more robust layer system though – at this time I am always a bit insecure utilizing the layers.
My goal with The Cannibal Polypaint was to capture the richness of the face. I was very comfortable with ZBrush doing this.