Using Polygroups to Move the Mouth
The same problems with sculpting the ears also manifest when you’re trying to move the lips independently of one another. When trying to mask or move the upper lip, you will often find the lower lip is moved as well due to their proximity to each other. The brushes will simply affect anything underneath their falloff rings that isn’t masked. The solution to this is to polygroup the lower lip separately from the rest of the head. This makes it very simple to grab one part of the mouth and quickly manipulate it while sculpting.
To polygroup the mouth, we will use steps similar to those we used with the ear, but we first need to mask the lips separately from each other. This can be difficult since the lips are so close; masking one lip invariably seems to create a mask on part of the other. We will need to spread the lips open.
1. Store a morph target of your model by selecting Tool + Morph Target and clicking the StoreMT button. This creates a copy of the mesh shape in memory that you can easily return to. You are storing this morph target because you will now stretch the mouth open to facilitate masking the lips. By returning to the stored shape, you can correct any changes made to the mouth while keeping the mask.
2. Select the Smooth brush and smooth the mouth area. This will have the effect of spreading the mouth faces open. You can also get good results using the Inflate brush set to ZSub, as this will push faces apart (Figure 3.25).
Figure 3.25 Opening the mouth with the Smooth brush
This process is somewhat involved, so you would not want to repeat it each time you want to open the mouth. Although the mesh is masked, we can easily create a polygroup; therefore, hiding one half of the mouth is easier.
3. With the lower lip still masked, select Tool ->· Visibility and click the HidePt button HidePt will hide any unmasked faces. With the lower lip visible, you can now polygroup it separately from the rest of the head (Figure 3.26).
ZBrush 4 introduced a new brush mask called Topological Masking to help alleviate the issue of moving clips and other objects that may be close together, such as toes. Access this setting by choosing Brush + Auto Masking + Topological Masking (Figure 3.27). The Range slider will control how far from the center of the brush the effect will carry.
The brush will only affect those points topologically close to the brush center, not physically close. This means you can move the upper lip independently of the lower because they are only physically close while topologically the points are far apart. Topological Masking is a useful tool and I recommend using it whenever possible. I still polygroup the lower lip as we showed earlier since I find sometimes it is faster to hide the mask and manipulate the jaw rather than enable Topological Masking and adjust the Range slider. Each approach has its strengths and you will be well served to explore both. The Topological Masking setting is invaluable when working on the toes, for example.
Figure 3.26 Polygrouping the lower lip
Figure 3.27 The Topological Masking settings under the Brush menu
Setting Up GoZ and Subtool Master
In this section we will be using two ZBrush plug-ins, GoZ and Subtool Master. Subtool Master allows you to perform various functions on multiple subtools. We will use it to mirror parts across the X axis. GoZ allows you to move your work seamlessly between ZBrush and another 3D application. We will use it to add geometry to our creature head.
The Subtool Master plug-in is available for free download from www.pixologic.com. The GoZ plug-in is preinstalled with ZBrush but you have to set it up (see the next section, “Installing GoZ”). Make sure both tools are ready for use before you proceed.
You install Subtool Master by extracting the contents of the zip file to the ZBrush4/ ZStartup/ZPlugs folder. GoZ requires a different setup.
Installing GoZ
GoZ comes preinstalled with ZBrush. All you have to do to enable it is click the GoZ button and ZBrush will search for all the applications it is capable of connecting with. When you encounter an application that ZBrush cannot find, it gives you the option to browse to that application’s location or select Not Installed. So, for instance, if you do not have 3ds Max installed on your machine, then you click Not Installed.
The installer will copy scripts into a common folder for the 3D application to use. This will require that you use administrator privileges on your machine during the installation. Once it’s installed, you can take advantage of GoZ’s functionality. If you set the GoZ application to Maya, you will now have a shelf in Maya with a GoZ button. In some cases this particular functionality does not work and you have to add the shelf manually. The following steps show you how to enable the GoZ shelf in Maya:
1. To set up the shelf in Maya, open the Script Editor window in Maya (Figure 3.28).
2. Click File Source script and browse to C:\Users\public\Pixologic\GoZApps\Maya. Here you will find the scripts that allow you to transfer work from Maya back to ZBrush.
3. Select the file called GoZScript.mel and run the script to create a GoZ shelf in Maya (Figure 3.29).
Sculpting a Character Bust
In this section, you’ll sculpt a character from the generic human head bust (Figure 3.30). This ZTool is prepared with mouth and ear polygroups to facilitate a quick sculpting workflow when dealing with these areas. You’ll also add new parts to the head directly using the Insert Mesh function. In the course of this exercise, you’ll make use of the Gravity Brush modifier as well as Transpose. You’ll also use the Subtool Master plug-in later in this exercise. Be sure to download and install this free tool from www.pixologic.com before you begin.
1. Initially you know that you want this character to be leaning his head back and grinning. The orientation of the head you want is different than that of the generic head mesh. To accomplish this change, use Transpose to shift the orientation of the head on the shoulders. To do this, snap to a side view and mask the shoulders with a lasso. Switch to Transpose Move by pressing the W key and shift the head back slightly (Figure 3.31). Subdivide the mesh by pressing Ctrl+D, and using the Standard brush,build up the anatomy of the neck—at this stage just suggesting the form and direction of the sternomastoid and clavicle.
Figure 3.28 Maya Script Editor window
Figure 3.29 The GoZ shelf in Maya
Figure 3.30 This character bust was sculpted from the generic human head mesh.
Figure 3.31 The head shifted back with Transpose Move
2. Now let’s take advantage of the ear polygroups to change the ear shape. Ctrl+Shift-click the ear to hide the head. Using the Move brush, adjust the ear shape into a more monstrous form (Figure 3.32).
3. Using the Move brush, stretch the mouth back, starting to suggest a grin. At this stage, you can widen the neck and shoulders to give the character a muscular look (Figure 3.33).
4. Taking advantage of the polygrouped mouth, let’s open the mouth by masking and moving the shapes (Figure 3.34). At this point let’s also add teeth to the model. (The teeth in this example were modeled by Jim McPherson.) Import them into the Tool palette, and then append them to the model as a subtool. Using the Transpose Move and Scale options, place the teeth in the head. Notice that the teeth here are upside down— I liked the ferocity that this underbite suggested, so I left them flipped (Figure 3.35). At this stage also add polymesh spheres as eyeballs.
Figure 3.32 Isolating the ear and changing its shape
Figure 3.33 Creating the grin and adjusting the shape of the shoulders
You can sculpt the teeth and gums independently of each other by using one of the Move brush variants new to ZBrush 4. The Move Parts brush will only affect the first part you click on when working with a single subtool composed of separate pieces, as is the case with the teeth. The Move Parts brush allows you to shift the teeth around and create irregularities quickly (Figure 3.36). To sculpt on the teeth without affecting them all at once, use polygroup masking. You’ll find Mask By Polygroup under the Brush + Auto Masking menu. Set the slider to 100 for any brush, and the brush effect will be applied only to the first polygroup you click. This is useful, for example, when you’re trying to sculpt striations in the tooth enamel without wanting to affect the gum tissue. For this technique to work, the teeth and gums must have separate polygroups (Figure 3.37). You can accomplish this by clicking Tool + Polygroups + Auto Groups.
5. To sculpt the forms of the ear, add another subdivision level and mask out inside the helix of the ear. Invert the mask, and using the Standard brush set to ZSub, carve away the negative space and start to introduce the ear forms (Figure 3.38).
Figure 3.34 Opening the mouth using polygroups
Figure 3.35 Teeth imported and placed
Figure 3.36 Quickly create irregularities with the Move Parts brush.
6. Using the Standard brush and alternating between ZAdd and ZSub, carve in the flow of major folds of flesh around the mouth and in the forehead. Take care to make the skin seem compressed at the cheeks by making deep recesses and high puckering rolls to help create the impression that the big mouth is stretching open. We can start to refine the anatomy of the neck, so also use InteractiveLight to move the light around and check the forms under different lighting conditions. Remember that this utility will only work with the standard materials and not the MatCap materials. For this example, we’re using the BasicMaterial.
7. Since this character is intended to be very fat, you want to add fleshiness and folds to the cheeks and under the chin. Using the Elastic brush set to ZAdd, start massing out the fat underneath the chin. Elastic is similar to Inflate, but it tries to maintain the forms already sculpted and tends to be less destructive of the area you are sculpting over (Figure 3.39).
Figure 3.37 Polygroup masking helps you sculpt each tooth and the gums separately.
Figure 3.38 Sculpting the forms of the ear
8. Let’s make further refinements to the shapes of the face (Figure 3.40). Use the Smooth brush on a low intensity to soften the forms. Create tight puckers between the folds of flesh by using the Inflate brush along the space where two folds meet. This has the effect of creating the look of two folds of skin pressing together.
9. Now use the Gravity modifier on the Elastic brush to add a sense of weight to the skin folds. Gravity is acting on our bodies at all times, but it is most apparent in loose-hanging skin like this character’s jowls. Figure 3.41 shows two forms. The form on the left has no sense of gravity, whereas the one on the right has a sense of weight and drag. By adding more body to the bottom of the fold, it appears that the fatty tissue is being pulled down by gravity. This applies to skin folds, finer wrinkles, and even cloth. The Gravity brush tries to automate this process by adding to the surface in the direction of the Gravity arrow (Figure 3.42). You can use Gravity on any brush by simply raising the Gravity slider value under the main Brush menu (Figure 3.43).
Figure 3.39 Adding fat to the neck with the Elastic brush
Figure 3.40 Stroke the Inflate brush between two folds to draw them together in compression.
Figure 3.41 This figure illustrates gravity and its effect on form. The right image is the sculpted form; the left represents the silhouette of the shape depicted. By adding more visual weight to the bottom of a form, you can create the impression that gravity is acting on it.
Figure 3.42 The Gravity brush modifier
10. The form is nearly finished and the sculpt is showing a strong sense of character (Figure 3.44). Turn off X Symmetry by pressing the X hotkey and start to “break” symmetry. Breaking symmetry means adding asymmetrical elements to different sides of the head to combat the perfect 3D look.
Figure 3.43 Using the Elastic brush with Gravity to add weight to the flesh folds
Figure 3.44 The final form development
