Chapter 15

Fur, Hair, and Clothing

The Autodesk® Maya® software offers a number of tools for adding fur, hair, and clothing to characters. Creative use of these tools adds believability and originality to your animated characters. In addition, many of these tools can be used to create engaging visual effects. This chapter takes you through a number of techniques that you can use to add fur, hair, and clothing to characters.

In this chapter, you will learn to:

• Add fur to characters
• Add dynamic motion to fur
• Create dynamic curves
• Add hair to characters
• Style hair
• Use hair constraints
• Paint nCloth properties

Adding Fur to Characters

In this section, you’ll add Maya Fur to a model of a hound dog’s head. Maya Fur can be used on NURBS, polygon, and subdivision surfaces. There are some limitations when using NURBS and subdivision surfaces. For instance, rendering fur on trimmed NURBS surfaces can add to render time, and many of the paintable fur attributes do not work when using subdivision surfaces. For this reason, we recommend that you use polygon geometry whenever possible.

Maya Fur works best for short-haired characters or characteristics such as eyebrows and facial hair. Think about using fur for hair that would be two inches or shorter in the real world. If your character’s hair is longer than that, then consider using Maya Hair, or Paint Effects.

Preparing Polygons for Maya Fur

Polygon models need to have properly mapped UV coordinates that lie within a 0 to 1 range in texture space. You should make sure that there are no overlapping UVs. This can cause problems and may even crash Maya when rendering.

Try to maintain consistency in texture space as you create UV coordinates. Seams between separate UV shells and between parts of the model’s texture coordinates are easily seen in the distribution of fur across the surface, and they can be difficult to eliminate. Figure 15-1 shows an example of a visible seam in the fur attached to the hound dog model. This seam appears because the end of the nose is a separate shell from the rest of the hound’s head. In some cases, it may be impossible to eliminate all seams.

Figure 15-1 A seam is visible in the fur on the nose of the hound.

The best strategy is to place UV seams on parts of the surface that are less noticeable than others. Once you have an understanding of how fur works after completing this chapter, you should test a simple fur preset (such as the duckling preset found in the Visor) on your models as you map the UV texture coordinates. You’ll see where the problem areas are before you spend a great deal of time perfecting the fur itself. Props such as clothing can also be used strategically to hide UV seams.

Chapter 11, “Texture Mapping,” has detailed information on how to create UV texture coordinates for polygon models.

In this example, the hound model has been created and the UVs have been properly prepared.

The UVs for the houndHead model are displayed in the UV Texture Editor (see Figure 15-2).

Figure 15-2 The UV texture coordinates have already been created for the houndHead model.

If you are applying fur to a subdivision surface, you may want to convert the model to polygons first and prepare the UVs before applying the fur. You can convert the model to subdivision surfaces after the fur has been applied. Working with subdivision surfaces and polygons is covered in Chapter 4, “Modeling II.”

Creating a Fur Description

The fur description node contains all the settings for the fur, such as length, color, width, density, and so on. A single fur description node can be applied to more than one surface.

A number of preset fur descriptions are available on the Fur shelf or by clicking the Presets button in the Attribute Editor for the fur description node. You can use a preset as a starting point. In this exercise, you’ll build the fur description from the default fur settings.

Figure 15-3 The fur is displayed as long spikes on the surface. Locators must be visible in the perspective view in order to display the spikes.

To see a version of the scene up to this point, open the hound_v02.ma scene from the chapter15scenes folder at the book’s web page.

Editing the Fur Description: Baldness

There are several ways to design the look of fur applied to your model. You can adjust the slider settings in the fur description node to create an overall look for the fur, or you can apply texture maps to the fur settings. These texture maps can be procedural nodes (such as ramp, fractal, or checker), or they can be file textures painted in other programs. You can also use the Artisan Brush tool to paint settings directly on the model. In this section, you’ll use Artisan to determine where fur grows on the model.

Fur is applied uniformly across the surface of a model. To control exactly where the fur grows, you’ll use the Baldness attribute. The Baldness value ranges between 1 and 0. The confusing aspect about the Baldness setting in particular is that a setting of 1 means fur covers the surface. A setting of 0 means the fur does not grow at all. This is confusing because intuitively more baldness (higher values) should mean less fur. In Maya, the settings are reversed so that a higher Baldness values mean more fur. Fortunately, this is the only setting that suffers from this counterintuitive behavior.

Settings between 0 and 1 determine the sparseness of the fur. Using a low Baldness setting, such as 0.1 or 0.2, might work well when creating whiskers for a man’s face.

In this exercise, you’ll apply Baldness values so that fur does not grow on the end of the nose, in the eye sockets, or on the inside of the mouth.

Fur Global Scale

You can also reduce the length of the fur by reducing the Global Scale value (as shown here). However, refrain from adjusting this slider when you first edit a new fur description, because the slider should be used to keep all the fur settings consistent when the model itself is scaled. For example, if this model and its fur are imported into a scene that requires the model to be resized, you can adjust the Global Scale value of the fur based on the scaling values applied to the model, and the look of the fur should remain consistent when rendered. If you adjust Global Scale before designing the fur, it may make it hard to adjust the settings properly if the model is scaled.

---

Figure 15-4 The painted-on surfaces of the hound turn black as you paint the Baldness value on the model. The fur spikes disappear in the black areas.

Figure 15-5 Use the Paint Fur Attributes tool to remove fur from inside the eye sockets.

Figure 15-6 Remove fur from the lips by painting from the inside of the model.

When you save the scene, the maps that you have painted for the fur attributes are saved to disk. You can find them in the current project’s furfurAttrMap folder. The maps are saved in the Maya IFF format.

Figure 15-7 An unnamed map is listed in the Maps section for the Baldness attribute.

If you reopen the scene, the UNNAMED label is replaced in the Maps section of the Attribute Editor for the houndFur node with the path to the baldness map that has been saved to disk (see Figure 15-8).

Figure 15-8 When you reopen the scene, the UNNAMED label is replaced with the path to the baldness map that has been written to disk.

Editing the Fur Description: Direction

You can use the Artisan Brush interface to comb the fur by painting the Direction attribute:

Figure 15-9 Observe the direction of the fur in this photo of an American foxhound.

Figure 15-10 Paint the direction of the fur on the surface of the hound. Increase the U and V Samples in the FurFeedback node to 256 to make it easier to see details in the fur direction.

To see a version of the scene up to this point, open the hound_v04.ma scene from the chapter15scenes folder.

Painting Across UV Texture Borders

As you paint across UV borders on the model, you’ll see the hair suddenly flip around. Since fur relies on UV texture coordinates to determine how the Polar attribute affects direction, as you move from one part of the texture space to another the polarity of the fur can suddenly change (a good example of this occurs on the back of the hound’s head). This may drive you crazy. To help deal with these problems, select the model, and choose Display ⇒ Polygons ⇒ Texture Border Edges. This makes the border edges of the UV coordinates visible as bold lines on the surface of the model. You can also reduce the size of the brush so that you can more easily paint specific areas along the border. With some patience and work, you’ll be able to make the direction of the fur consistent across the UV texture border.

---

Editing the Fur Description: Length

You can edit the Length attribute using the Paint Attributes tool as well. When editing lengths, you need to pay attention to the values used in the options for the Artisan Brush. For the hound, the fur is short near the end of the nose, is medium length on the face, and is long on the back of the head and neck. Values of 0.1, 0.25, and 0.5, respectively, were used on the aforementioned areas. To even out the transition between the fur lengths, set Paint Operation to Smooth, and paint the areas on the border between the different lengths of fur.

To see a version of the scene up to this point, open the hound_v05.ma scene from the chapter15scenes folder.

After painting fur lengths, you may decide to touch up the Direction attribute of the fur as well. You can change the paint operation mode (from Length to Direction, for example) in the Paint Fur Attributes Tool Settings pop-up whenever you need to, but remember that Maya may pause for a few moments to update the maps when you change attributes.

Baking Textures into Maps

You can use a procedural texture node (such as a ramp, fractal, or checker) as a starting place for a fur attribute map, as shown here. This works well when you are painting fur applied to a NURBS surface, since the UV texture coordinates are based on the parameterization of the surface itself. If you create a texture by clicking the Create Render node icon, you will need to bake the attribute before seeing the results. To do this, open the Attribute Editor for the FurDescription node. Set the Bake attribute to the desired attribute, and click the Bake button.

To see the Bake attribute in action, open the rampBaldness.ma scene from the chapter15scenes folder at the book’s web page.

A good use for this technique would be to apply fur as grass to a NURBS plane. You can use a fractal texture to create procedural variation in baldness or length to make the grass appear patchy.

---

Test-Render Fur

Now that you have the basic fur description created for the houndHead, you may want to see what it looks like when rendered. You can render the scene using either the mental ray® or Maya Software. The results should be fairly similar. In this example, you’ll use mental ray:

Figure 15-11 Choose the Production Rapid Fur preset on the Quality tab of the Render Settings window.

Figure 15-12 Create test renders of the fur as you adjust the settings.

To see a version of the scene, open the hound_v06.ma scene from the chapter15scenes folder.

The fur should cover the model completely; however, you will notice that some attributes, such as the baldness map and the direction, may require further editing.

Applying a Color Map

Adding a texture map to the color greatly helps the realism of the fur. You can increase the efficiency of the render by applying the same file texture to the fur color and the shader as applied to the model. This technique should work as long as the model does not get extremely close to the camera.

A texture map that has been carefully painted in Photoshop or in a 3D texturing program works better than a map created by painting color on the fur. In this case, ZBrush was used to create the color texture map for the hound model.

Figure 15-13 Drag the file1 node from the Textures tab of the Hypershade onto the Base Color channel of the houndFur node.

Figure 15-14 Add a color map to the fur description (left image), and render the scene shadows (right image).

To see a version of the scene, open the hound_v07.ma scene from the chapter15scenes folder.

Applying Map Offsets and Multipliers

In the Details section of the houndFur node, you’ll notice that each attribute has Map Offset, Map Multiplier, Noise Amplitude, and Noise Frequency settings. These sliders can apply an additional adjustment to the fur map attributes.

The Map Offset and Multiplier attributes are used to change the range of values for any of the attributes. Most of the attributes are limited to a range between 0 and 1, which corresponds to the grayscale values painted on the surface with the Paint Fur Attributes brush. If you would like to change the range so that it can go beyond 1, you can use Map Offset or Map Multiplier.

Offset adds a number to the overall range. If you want to offset the range for an attribute so that, instead of a range of 0 to 1 the range becomes 2 to 3, set Offset to 2.

If you want to expand or diminish the range of values, use Multiplier. For example, if you want the range of a value to be between 0 and 10 instead of 0 to 1, set Multiplier to 10.

The Noise Amplitude and Frequency sliders add randomness to the map values.

Figure 15-15 Shorten the overall length of the hair by reducing the Multiplier value for the Length attribute. Add variation to the tip color by adding noise to the Tip Ambient Color attribute.

To see a version of the scene, open the hound_v08.ma scene from the chapter15scenes folder.

Enhancing the Realism of Fur

The basic fur description for the hound has been created, but to make it look realistic, a fair amount of editing still needs to be done. There are many additional attributes you can use to help accomplish this. This section describes how these attributes work. As with the Baldness, Length, Direction, and Color attributes, you can use a single value to determine the overall setting for each attribute, paint values for the attribute on selected areas, or use a texture map to determine the strength of the selected values.

Inclination, Roll, and Polar are attributes that determine the direction that the fur is pointing along the surface of the model. As noted, Inclination determines whether the hair points straight up from the surface (at values closer to 0) or lies along the surface (at values closer to 1). The Roll setting rotates each hair around the base, and the Polar attribute determines the direction the fur points along the surface. Roll and Polar can be used together to fine-tune the direction of the hair. If you have painted a map for the Direction attribute using the Paint Fur Attributes tool, changing the Polar setting has no effect.

After painting a map for the Direction attribute using the Paint Fur Attributes tool, you may want to paint values for the Inclination and Roll attributes. This can help define more exactly the direction in which the fur points along the surface. You may find yourself switching back and forth among Direction, Inclination, and Roll as you edit the fur on the surface. If you need precise control over the styling of the fur, be prepared to spend some time working with these attributes.

Base Opacity and Tip Opacity are self-explanatory attributes. The base of the fur is the part of the fur strands closest to the surface; the tip is the part of the fur farthest from the surface. Opacity is applied as a gradient across the length of the fur. To create the look of soft, fine fur, set Base Opacity to 1 and Tip Opacity to a very low setting or even 0. You can experiment with these values to create special effects; try a low Base Opacity and a high Tip Opacity.

Base Width and Tip Width establish the shape of the fur strands. A small Tip Width coupled with a large Base Width produces a pointy shape for the fur. A very low Tip Width helps create the look of soft, fine fur.

The Base Curl and Tip Curl attributes add curl to the fur strands at the base or tip. A value of 0.5 produces no curling. A value of 1 or 0 produces curling in one direction or the other.

The Scraggle, Scraggle Frequency, and Scraggle Correlation attributes add random kinks to the hair to create a messy appearance. The Scraggle setting determines the strength of the scraggle. Scraggle Frequency determines how many kinks appear in each strand of fur. Scraggle Correlation determines how the Scraggle value of one strand affects another. A setting of 0 for Scraggle Correlation creates random kinks throughout the fur strands, and a Scraggle Correlation of 1 means all the fur strands kink the same way, creating a wavy appearance for the fur.

The Clumping, Clumping Frequency, and Clump Shape settings cause the fur strands to attract each other into bunches on the surface. This is useful for making a surface appear wet or matted. The Clumping setting sets the strength of the clumping, and Clumping Frequency determines the number of clumps created across the surface. Clumping Frequency ranges between 0 and 100; higher values take longer to render. Clump Shape determines whether the clumps themselves are convex or concave. Settings closer to –10 produce concave clump shapes, whereas settings closer to 10 produce convex clumps (see Figure 15-16).

Figure 15-16 Clumping is demonstrated on two planes. The plane on the left has a Clump Shape value of –10; the plane on the right has a Clump Shape value of 10.

Rendering Fur Using mental ray

You can render fur using mental ray or Maya Software. When rendering with Maya Software, you’ll need to add a fur-shadowing node to the lights in the scene. In this section, you’ll learn how to refine the look of the fur with mental ray.

If you plan to use depth map shadows, use the Production: Rapid Fur preset. If you plan to use raytrace shadows, use the Production: Fine Trace Render preset. If you need the fur to appear in reflections or refractions, use raytracing.

Fur renders use indirect lighting techniques such as Final Gathering. Be aware that the render times for dense fur descriptions when Final Gathering is enabled can be quite long.

To create a realistic render of the hound using raytracing, follow these steps:

Figure 15-17 Render the hound using raytrace shadows.

To see a finished version of the scene, open the hound_v09.ma scene from the chapter15scenes folder at the book’s web page.

You can continue to enhance the look of the fur by improving the texture maps applied to the fur description as well as by improving the lighting in the scene.

Maya Fur does a good job of creating fur effects for many typical situations. For truly stunning fur and hair effects, you may want to consider using the Shave and a Haircut plug-in developed for Maya by Joe Alter. This plug-in has been used for many feature films and television shows. For more information, visit www.joealter.com.

Animating Using Dynamic Curves

Dynamic curves are NURBS curves driven by the Nucleus dynamic simulation framework. The primary use of dynamic curves is to drive the dynamics of nHair systems applied to characters. They can also be used to drive fur. However, the usefulness of dynamic curves goes far beyond creating hair motion. Curves used to loft or extrude surfaces, curves used for Paint Effects strokes, curves projected on NURBS surfaces, curves used as IK splines, curves used as particle emitters, and so on can be made dynamic, thus opening up a large number of possibilities for creating additional dynamic effects in Maya. While working through the scenes in this chapter, you may want to set the timeline preferences to loop so that you can see the hair update continuously as you adjust its settings. To do so, follow these steps:

Using Dynamic Curves with IK Splines

In Chapter 7, “Rigging and Muscle Systems,” you learned about the IK Spline tool, which uses a curve to control the inverse kinematics (IK) of a joint chain. The curve itself can be converted into a dynamic curve that can be used to drive the IK Spline tool. This is a great way to add dynamic motion to a rig used for tails or tentacles.

In this example, you’ll use a dynamic curve to control a segmented armored tail. The armored tail consists of polygon pieces, each of which has been parent-constrained to a joint in a chain. The first step is to create a curve (see Figure 15-18).

Figure 15-18 The armored tail consists of polygon pieces constrained to a joint chain.

Figure 15-19 A number of nodes are added to the scene when a curve is made dynamic.

Figure 15-20 The dynamic curve droops as if it is attached at both ends to the original curve.

Figure 15-21 Move the pivot point of the follicle to the end of the curve.

To see a version of the scene, open the armoredTail_v02.ma scene from the chapter15scenes folder.

Creating an IK Spline Handle from the Dynamic Curve

In this section, you’ll create an IK spline handle for the armored tail and attach it to the dynamic curve. The dynamics of the curve will be edited to change the behavior of the tail.

Figure 15-22 Editing the Stiffness Scale curve changes the stiffness along the length of the dynamic hair.

The Stiffness setting creates the overall stiffness value for the dynamic curve. Stiffness Scale modifies that value along the length of the curve. Both settings, like almost all of the dynamic curve settings, can be animated.

To see a version of the scene, open the armoredTail_v03.ma file from the chapter15scenes folder.

Using Forces

The settings in the Forces section add levels of control for the curve’s motion. Play the animation in the armoredTail_v03.ma scene, and adjust these settings while the scene loops so that you can see how they affect the motion of the tail.

Adding Hair to a Character

Hair is created by attaching follicle nodes to a surface. Each follicle node controls a number of hairs. The follicles themselves are styled using a combination of control curves and forces. Follicles and control curves are connected to a hair system node. A single hair system node can control hair connected to any number of surfaces, and a single surface can be attached to multiple hair systems.

When you create hair, you have to consider how you plan to render it. You have the choice of creating Paint Effects strokes for the hair or curves that can be used to render in third-party engines such as Render Man, or creating both Paint Effects strokes and curves. Even though hair uses Paint Effects, it renders using mental ray without the need to convert the hair to polygons.

You can still use Classic Hair, located under nHair ⇒ Classic Hair, to build and style your character’s hair. Once nHair is created, you can toggle between Classic Hair and the Nucleus Solver from within the hair system shape node’s Attribute Editor. In this section, you’ll create and style hair for a character using nHair and the Nucleus framework.

Applying Hair to a Surface

When you want to apply hair to a character, you can either apply the hair uniformly to the entire surface or paint the hair selectively on parts of the surface.

It is common practice to create a nonrendering scalp surface that can be parented to a character’s head and then apply the hair to the scalp surface rather than directly to the character’s head. This allows flexibility because scalp surfaces and their attached hair can easily be swapped between characters. It also speeds up playback in the animation because the hair dynamics are not factored into the calculations required to deform the character’s surface if it has been skinned to a skeleton or to other deformers.

Some animators like to apply separate hair systems to each part of the scalp to control the various sections of a particular hairstyle. For instance, one hair system may be applied to the bangs that hang over the character’s forehead, whereas another system may be used for the hair on the back of the head. In this exercise, you’ll keep things simple by using a single hair system for the character’s hairstyle. Both methods are valid, and as you become comfortable working with hair, you may want to experiment with different techniques to see which approach works best for you.

The following procedure uses the Nancy Hair scene, which contains the rigged nancy character used in Chapter 6, “Animating with Deformers.” The head is rigged to a series of joints. You can select and rotate the headCtrl curves above the head to change the position of the head. A scalp surface has been created by duplicating part of the head geometry. This scalp geometry is parent-constrained to one of the joints in the head rig.

You can apply hair to NURBS or polygon surfaces. When you use polygon surfaces, the UV texture coordinates must be mapped so that none of the UVs overlap and the coordinates fit within the 0 to 1 range in the UV Texture Editor. As with fur, you’ll get better results from your hair system if the UV coordinates have been carefully mapped. Remember to delete history for the surface once you have created UV texture coordinates to keep the coordinates (and attached hair) from moving unpredictably during animation.

Figure 15-23 The Create Hair Options area

Figure 15-24 The hairs appear as long spikes on the top of the head. When you click the Play button, the hairs fall and settle into a basic hair shape.

To see a version of the scene, open the nancyHair_v02.ma scene from the chapter15scenes folder.

In the next section, you’ll learn how to style the hair.

Determining Hair Shape

A number of settings in the hair system node determine the look of the hair. These are found in the Clump and Hair Shape section of the hair system’s attributes.

Figure 15-25 Adding and moving points along the various edit curves can shape the overall look of the hair.

Figure 15-26 Establish the basic shape of the hair using the settings in the hairSystem1 node.

To see a version of the scene, open the nancyHair_v03.ma scene from the chapter15/scenes folder.

Styling Hair

Once the hair has been set up, you can use a number of tools to style the hair. You can use dynamic fields as a hair-styling tool, paint follicle properties on the hair, or even manipulate the CVs of control curves.

Start and Rest Positions

Before styling the hair properly, you should create a start position for the hair, so that the animation does not start with the hair sticking straight out of the head. Doing so makes styling much easier.

The start position represents the shape of the hair at the start of the simulation. The rest position represents the hair’s shape when no forces are acting upon it. These are very similar, but you can distinguish between the two by thinking of it like this: imagine an animation where a character is jumping up and down and then stops. The animation starts with the character in midair. You want to set the start position to represent what the hair looks like when the character is in midair. Once the character stops jumping and the hair settles, the hair assumes its rest position. For some animations the start and rest positions may look exactly the same; at other times, such as in the example described, the start and rest positions look different.

Hairstyle Presets

Maya comes with a number of preset hairstyles in the Visor, as shown here. You can open these by choosing (from the nDynamics menu set) nHair ⇒ Get Hair Example. To use a hairstyle, right-click one of the icons and choose to import the file into your scene. Each preset style comes with hairline geometry that can be parented to your character’s head. Or you can copy the style using the Transplant Hair option.

---

To see a version of the scene, open the nancyHair_v04.ma scene from the chapter15scenes folder at the book’s web page.

Painting Follicle Attributes

Using the Artisan Brush interface, you can paint follicle attributes. Before doing this, you must make sure that the hair is in its rest or start position. Some attributes, such as Inclination, require that the animation be on frame1.

Figure 15-27 Trim the hair at the front of the head using the Paint Hair Follicles tool.

To see a version of the scene, open the nancyHair_v05.ma scene from the chapter15scenes folder.

Modifying Curves

You can modify curves directly by moving their CVs or by using the tools in the Hair ⇒ Modify Curves menu. By modifying curves directly, you can fine-tune a style.

You can modify only start or rest curves. To do this, use the Show menu in the viewport window to disable the visibility of strokes in the scene, and choose nHair ⇒ Display Rest Position (or Start Position). Select the curve (or right-click the curve, and choose Control Vertex to work just on selected CVs), and apply one of the actions listed in the nHair ⇒ Modify Curves menu. You can also edit the shape of the curve directly using the Move tool to change the position of CVs on the curve (see Figure 15-28).

Figure 15-28 Modify the CVs of a start curve using the Move tool.

As you are editing the curve, you can lock the length so that the changes you make do not stretch the curve beyond its original length. Select the curve, and choose nHair ⇒ Lock Length (or use the l hot key). Conversely, you can unlock the curve if you want to change its length.

Curling, Noise, Sub Clumping, and Braids

Curling, Noise, and Braids all work best when the Sub Segments attribute in the Clump and Hair Shape section of the hair system node is increased. You can find the Curling and Noise settings in the Displacement section of the hair system node.

The Sub Clumping setting causes the hair within clumps to bunch together. This helps when you are creating wet or kinky hair.

The Braid option is available as an attribute for individual hair follicle nodes. For a braid to work successfully, you may need to alter the clump shape and the hairs per clump. It may be a good idea to use a separate hair system to create a detailed braid.

Rendering Hair

Rendering hair can be done using Maya Software or mental ray. The hair should be either Paint Effects strokes or Paint Effects strokes converted to geometry. Paint Effects strokes are discussed in detail in Chapter 8, “Paint Effects.”

Rendering hair is a straightforward process. If you’re not familiar with Paint Effects, you should review Chapter 8 before reading this section.

When you convert hair to geometry, the Hair Tube shader is automatically applied. You can render Paint Effects hair using mental ray without the need to convert the hair to geometry.

When you are ready to render the hair, you’ll want to increase the Hair Sub Segments setting in the hairSystem node's Attribute Editor, as well as Hairs Per Clump, Hair Width, and Hair Width Scale, in order to create fuller hair. You can always add follicles as well using the Paint Follicles tool.

In the Render Stats section of the hairSystem node, you can enable Receive Shadows, Visible In Reflections, and Visible In Refractions when rendering with mental ray. On the Quality tab of the mental ray render settings, you can use the Rapid Motion Hair preset to render hair without raytracing or the Production: Fine Trace preset for rendering with raytracing. If the hair will not render using mental ray, make sure the Render Fur/Hair setting is activated on the Features tab of the mental ray Rendering section.

In this scene, the dreads.mel preset, found on the Hair Examples tab of the Visor, is applied to the nancy model. The hairLights.mel file has also been imported from the Visor and applied to the scene.

The scene is set up to render using mental ray. The render will take a couple of minutes. Figure 15-29 shows the results (shadows have been enabled for the lights in the image).

Figure 15-29 Apply the dreadlocks preset hair to the nancy model, and render it with mental ray.

Most standard lights will render hair nicely. When you’re testing the look of the hair, using the hairLights.mel preset makes it easy to see how the hair will look when rendered.

Creating Clothing for Characters

In this section, you’ll explore techniques for using nCloth to add dynamic motion to a character’s clothes. The example files are simple, but you can use the same techniques for more complex characters and models.

The Nucleus solver divides its computations into multiple threads for self-colliding surfaces and stretch resistance. Additional threading is also used to speed up playback of simulations with multiple nCloth objects on the same solver. Before starting this section, you should review Chapter 13 (“Introducing nParticles”) and Chapter 14 (“Dynamic Effects”) so that you understand how nDynamics and the Nucleus solver work.

Modeling Clothes for nCloth

The models you create for use with nCloth must be polygon meshes. Beyond that, there is nothing special about how you model your clothing. Smooth mesh polygons work just as well as standard polygons. You’ll start by taking a look at an example scene.

This scene has a simple cartoon character that has been rigged and animated. The character has a shirt and pants that have been created using standard polygon modeling techniques. Both objects are currently smooth mesh polygons. The scene has been arranged so that the display layers contain the major components of the model and the animation rig.

Figure 15-30 The simpleMan_v01.ma scene contains a simple cartoon character. Clothes have been modeled using polygons.

Figure 15-31 When you play the scene, the character’s pants fall down.

The first step in preventing the pants from falling is to make the character’s body a Passive Collider object. It does not matter that the character is already rigged and animated. However, it’s a good idea to convert the polygons to nCloth objects (both nCloth and Passive Collider objects) when the character is in the default pose and there are no intersections between the nCloth and Passive Collider geometry.

To see a version of the scene, open the simpleMan_v02.ma scene from the chapter15scenes folder.

In the next section, you’ll create a constraint that will keep a character’s pants from falling down.

Using Constraints

The simplest way to keep the character’s pants on is to create a transform constraint. A transform constraint attaches the selected vertices on an nCloth object to the pivot point of another object without affecting the position of the nCloth vertices. When the constraining object is translated or rotated, the vertices follow along, dragging the rest of the nCloth object with them.

Figure 15-32 Select the edges at the top of the pants (left image). Convert the edge selection to vertices (center image). When you constrain the vertices to the rootCtrl locator, the pants stay up and collide with the animated character (right image).

To see a version of the scene, open the simpleMan_v03.ma scene from the chapter15scenes folder at the book’s web page.

You can also constrain objects to components of nCloth objects, such as vertices. Using this technique, you can easily simulate the effect of buttons holding a shirt together.

Figure 15-33 The surface of the shirt intersects the pants in the back of the character. Use the Move tool to move the faces of the shirt outward to fix the problem.

Figure 15-34 As the character moves, the front of the shirt flies open.

Figure 15-35 Select vertices near the collar, and turn them into a constraint (left image). Then create four pairs of constraints on the front of the shirt (right image).

Figure 15-36 When you play the animation, the shirt stays closed as if it has buttons.

To see a version of the scene, open the simpleMan_v04.ma scene from the chapter15scenes folder at the book’s web page.

Maya 2014 adds a new type of constraint called simply Component. The Component constraint differs from the Component To Component constraint you just used; you can use it to replace nCloth’s internal Stretch constraints. As a result, you gain a high level of individual control. The following steps demonstrate the process and the potential for the Component constraint.

Figure 15-37 Select the vertices of the shirt minus the sleeves.

Figure 15-38 The default attributes of the Component constraint

Figure 15-39 Without any resistance, the sleeves stretch with gravity.

Connecting Buttons to the Shirt

You can connect buttons to the shirt geometry using the Point On Poly constraint:

Figure 15-40 Select the vertices toward the top of the shirt, and then Shift+click the button.

Figure 15-41 The Offset fields are used to rotate and translate the constrained button into the correct position.

To see a version of the scene, open the simpleMan_v05.ma scene from the chapter15scenes folder at the book’s web page.

You can also select a face of a polygon object and use the Point On Poly constraint to attach an object to a polygon face.

Applying Forces

You can use wind or a directional force to move an nCloth object. You can assign these locally, affecting the object and leaving all other nCloth objects unaffected. This feature can be useful to give elements such as capes a cinematic feel. The settings to modify a local force or local wind are located on the nCloth shape node (see Figure 15-42).

Figure 15-42 The Local Force and Local Wind settings

Painting nCloth Properties

nCloth properties can be painted to gain detail in your simulation. You can paint properties such as Bounce, Stretch, and Wrinkle onto an nCloth object. All the properties can be painted as vertex maps or texture maps.

When you paint a vertex property map, you paint property values directly onto the vertices of the object, similar to painting smooth skin weights for joints. The more vertices you have in your object, the more detail you can create for your vertex property map. The vertex map values are saved with the object, so you do not need to link to external map files.

Texture property maps are independent of the number of vertices in the object, but they do require that UVs are properly created for the object, meaning that the UVs do not overlap and do remain within the 0 to 1 range in the UV Texture Editor. Texture property maps for nCloth objects are similar to texture property maps created for fur. However, you do not need to bake the maps after applying them.

When you paint a vertex or texture map, the map is listed in the Attribute field in the Dynamic Properties section of the nCloth shape node’s Attribute Editor.

In this example, you’ll paint Wrinkle attributes for the simple man character’s pants. A wrinkle map displaces an nCloth object to create folds in the surface. You can paint detailed wrinkles into objects with a lot of vertices. In this example, you’ll use the wrinkle map to add cartoonish embellishments to the pants, which have a fairly low number of vertices.

When applying a Wrinkle attribute, positive values push the nCloth outward, while negative values push it inward. There are a few peculiarities about painting Wrinkle values, which you’ll explore in this exercise:

Figure 15-43 When you create the wrinkle map and play the animation, the pants bloat outward. When you apply the value 0 to all the vertices, the pants turn black and the shape returns to normal.

Figure 15-44 You can adjust the Min/Max value fields to allow for a wider range of values for the Paint nCloth Attributes tool. Adjusting the Min Color and Max Color sliders allows you to visualize the new values painted on the surface.

Figure 15-45 Paint a value of -0.2 around the belt area of the pants. Paint positive values near the pant cuffs to create flares.

To see a version of the scene, open the simpleMan_v06.ma scene from the chapter15scenes folder.

To learn more about fur, hair, and nCloth, check out Maya Studio Projects: Photorealistic Characters (Sybex, 2011).

The Bottom Line