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54_381304-ch41.qxp 7/7/08 2:28 PM Page 997 Working with Inverse Kinematics The easiest way to use this IK solver is to select SplineIKSolver from the drop-down list in the IK Chain Assignment rollout while you’re creating the bone structure. After the bone structure is complete, the Spline IK Solver dialog box appears. With this dialog box, you can select a name for the IK chain, specify the curve type, and set the number of spline knots. The curve type options include Bézier, NURBS Point, and NURBS CV. You can also select to Create Helpers and to display several different options. Another way to use this IK solver is with an existing bone structure. To do this, you need a spline curve in the scene that matches how you want the bone chain to look. Then select the first bone where you want the solver to be applied, and choose Animation ➪ IK Solvers ➪ Spline IK. In the viewports, a dragging line appears; move the line to the last bone that you want to include, and then drag a second time to the spline that you want to use. The bone structure then assumes the shape of the spline curve. A helper object is positioned at the location of each curve vertex. These helper objects let you refine the shape of the curve. Tutorial: Building an IK Spline alligator The IK Spline solver is perfect for creating long, winding objects like snakes or an alligator’s tail. For this example, you’ll take an existing bone structure and, using the Spline IK solver, make it match a spline. To create a bone structure for an alligator that follows a spline using the IK Spline solver, follow these steps: 1. Open the Alligator spline IK.max file from the Chap 41 directory on the DVD. This file includes an alligator model created by Viewpoint Datalabs, a simple bone chain, the Skin modifier, and a spline. TIP If you’re having trouble seeing the bones located inside the alligator, you can enable the See Through option in the Object Properties dialog box or press the Alt+X keyboard shortcut. 2. With the first bone in the tail chain selected, choose Animation ➪ IK Solvers ➪ SplineIK Solver. A dragging line appears in the viewport extending from the first bone. 3. Drag and click the cursor on the last bone in the bone tail chain. 4. Another dragging line appears; drag and click on the spline, and the bone structure moves to match the spline’s curve. Figure 41.12 shows the bone structure for the gator’s tail. You can now control the gator’s tail by moving the dummy objects along the spline. 997 41 54_381304-ch41.qxp Part X 7/7/08 2:28 PM Page 998 Working with Characters FIGURE 41.12 The IK Spline solver is perfect for creating objects such as snakes and animal tails. Summary Inverse kinematics (IK) provides a unique way to control and animate hierarchical structures by transforming the child node. In this chapter, you accomplished the following:
Learned the basic concepts behind IK
Explored the difference between interactive and applied IK methods
Created and animated an IK system
Used the IK settings in the Preference Settings dialog box
Learned how to use IK solvers Now that you’ve learned the process for rigging a character and using IK, we’ll take a look at using Biped next and discover the benefits of using a pre-rigged skeleton. 998 55_381304-ch42.qxp 7/7/08 2:24 PM Page 999 Creating and Animating Bipeds and Crowds M ax has always had a great way to create and animate characters, but in early versions of Max, it was available only as a separate plug-in known as Character Studio. Happily, Character Studio has been integrated into Max to the point that it isn’t distinguishable as a separate package. In fact, some of Max’s original features have overgrown Character Studio, but much of Character Studio’s original, innovative features still exist and are extremely useful, including Biped. Using Biped, you can create a fully linked and constrained human-form skeleton by simply dragging in the viewport. Biped objects can be altered in many ways while retaining their benefit. The major benefit of bipeds is that you can realistically animate them by simply positioning their footprints or setting freeform keys. Although Max includes other features for rigging characters, if you plan on animating a character that walks on two legs and has two arms, then biped is definitely the way to go. It’s an incredible timesaver. Nobody likes crowds (except for certain types of bugs), but with the Character Studio’s Crowd Animation tools, controlling crowds can be lots of fun. The fun comes when you realize that you would spend weeks animating by hand all the actions that are possible with the Crowd animation tools. Characters included in a crowd simulation are called delegates, and these delegates can have assigned behaviors that tell them to follow a certain object or a certain path and to avoid designated objects. As you begin to simulate crowds, you’ll delight in how much it is like taking the whole family shopping together, except the delegates actually do what you say. Character Creation Workflow A typical workflow for creating characters in Max involves first creating a skin mesh object. After the skin mesh is complete, you can create a biped object to 999 IN THIS CHAPTER Learning the basics of Character Studio Creating and editing a biped Animating a biped using Footstep and Freeform modes Introducing the Biped applications Using Crowd and Delegates 55_381304-ch42.qxp Part X 7/7/08 2:24 PM Page 1000 Working with Characters drive its animation. The biped consists of a pre-rigged skeleton of bones that provide an underlying structure to the character. Animating these bones provides an easy way to give life to the character. With a biped created, position the biped within the skin mesh and match the bone links to the relative size and position inside the skin mesh. The bones do not need to be completely within the skin mesh given you can set the biped objects to not be rendered, but the closer they are to the skin mesh, the more accurate the movements of the character are. After the biped is sized and matched to the skin mesh, use the Skin modifier to attach the skin mesh to the biped. This automatically sets all the envelopes that govern which skin parts move with which bones. You can also use the Skin modifier settings to deform the skin at certain bone angles, such as bulging a muscle when the arm is raised. The original Character Studio package used the Physique modifier to bind the mesh skin to the biped. Although this modifier still exists and can be used, the Skin modifier includes many new features and is the preferred method for binding a mesh skin to the biped. NOTE The next step is to animate the biped using its animation tools, which can include walk, run, and jump cycles by placing footsteps or freeform animation using keys. Along the way, you can save, load, and reuse animation sequences including motion capture files. Animated sequences can be combined and mixed together to form a smooth-flowing animation using the Motion Mixer. Creating a Biped Creating a hierarchical skeleton that is used to control the animation of the mesh skin that is draped over it is quite easy when you create a biped. The skeleton can be set to be invisible in the final render and exists only to make the process of animating easier. Although Max includes a robust set of tools that can be used to create a skeleton of bones, the Biped feature automates this entire process using prebuilt skeletons. For some characters, manipulating a biped is more work than building a custom skeleton. For these occasions, you can manually create a skeleton structure. Building a skeleton system by hand is covered in Chapter 40, “Understanding Rigging and Working with Bones.” CROSS-REF To create a biped, simply select the Create ➪ Systems ➪ Biped menu command and drag in a viewport. The Biped menu command accesses the Biped button found in the Systems category of the Create panel. Figure 42.1 shows a default biped created by dragging in a viewport. The Create Biped rollout includes two creation methods: Drag Height and Drag Position. The Drag Height creation method lets you set the height of the biped by dragging in the viewport, and the Drag Position creation method creates a standard-sized biped and lets you position it by dragging about the viewport. NOTE To precisely position a biped on the surface of any existing object, enable the AutoGrid option at the top of the Object Type rollout. In the Root Name field, you can name the biped. Every biped bone is given a unique name, and this root name is attached to the front of the unique bone name. For example, if you specify Gloop as the root name, then the right calf bone is given the name Gloop R Calf. Below the Biped Name field is the Body Type drop-down list. In this list, you can select from Skeleton, Female, Male, and Classic body types. The differences among these body types relate to the size and shape of the bones. The Classic body type was used in previous versions of Character Studio and exists for backward compatibility. Figure 42.2 shows each of these body types. 1000 55_381304-ch42.qxp 7/7/08 2:24 PM Page 1001 Creating and Animating Bipeds and Crowds FIGURE 42.1 The default biped includes all the basic body parts for a human character. Open Fig File FIGURE 42.2 The four available body types include Skeleton, Female, Male, and Classic. By default, all biped bones are color coded, with all bones on the right side colored green and all bones on the left side colored blue. The pelvis, which is the root bone, is colored yellow, and the head is light blue. These colors help keep the different bones straight, and the same colors are used for the footprints that define the biped’s motion. 1001 42 55_381304-ch42.qxp 7/7/08 Part X 2:24 PM Page 1002 Working with Characters Customizing a biped Although the standard biped resembles a human form, you can use the settings in the Create panel to radically change the biped to resemble whatever creature you’ve created. Customized biped skeletons can be saved using the Save File button found in the Motion panel when Figure Mode is enabled. Biped files are saved with the .fig file extension. Saved biped files can then be recalled when a new biped is being created using the Open Fig File button in the Create Biped rollout. You can also select to create any new bipeds using the user interface settings or using the Most Recent .fig file. NOTE The Save File button saves the skeleton structure as a .fig file when Figure Mode is enabled and saves the animation sequence as a .bip file when Figure Mode is disabled. The Create Biped rollout includes settings for toggling the arms on and off. Settings are available for controlling the number of links used to represent all the various body parts listed in Table 42.1. These same settings are available in the Structure rollout of the Motion panel, which is available when Figure Mode is enabled. TABLE 42.1 Biped Parts Body Part Link Limits Arms On or Off Neck Links 1 to 25 Spine Links 1 to 10 Leg Links 3 to 4 Tail Links 0 to 25 Ponytail1 Links 0 to 25 Ponytail2 Links 0 to 25 Fingers 0 to 5 Finger Links 1 to 3 Toes 1 to 5 Toe Links 1 to 3 Props Up to 3 enabled Ankle Attach 0.0 (back of foot) to 1.0 (front of foot) Height unlimited Triangle Pelvis On or Off Triangle Neck On or Off Forefeet On or Off Twist Links On or Off Upper Arm Twist Links 0 to 10 1002 55_381304-ch42.qxp 7/7/08 2:24 PM Page 1003 Creating and Animating Bipeds and Crowds Body Part Link Limits Forearm Twist Links 0 to 10 Thigh Twist Links 0 to 10 Calf Twist Links 0 to 10 Horse Link Twist Links 0 to 10 (Leg links must be set to 4 to use Horse Links) Ponytail links are located on the back of the head and, like the arms, will naturally hang down when the spine bones are rotated. Tail links extend as expected off the back of the pelvis bone. Enabled Props appear as tall rectangular boxes attached to the hands. Prop1 is attached to the right hand, Prop2 is attached to the left hand, and Prop3 floats on the left side of the body. Figure 42.3 shows a biped with two ponytails, a tail, and a single prop. TIP Ponytail objects can be used to represent ears, horns, or a unique haircut that moves independently of the head. FIGURE 42.3 This biped includes two ponytails, a tail, and a prop object attached to its right hand. 1003 42 55_381304-ch42.qxp 7/7/08 Part X 2:24 PM Page 1004 Working with Characters The Triangle Pelvis option isn’t initially visible when creating a biped, but if enabled, the pelvis consists of two links that extend from the spine to where the leg links are located. This helps keep the leg joints from intersecting directly under the spine. You can also select to use a Triangle Neck bone, which extends to connect to the clavicle bones, helping deform the skin better. The Forefeet option causes the biped hands to act like feet, which is helpful for creating quadruped characters. NEW FEATURE The Triangle Neck and Forefeet options are new to 3ds Max 2009. The twist links feature allows body parts to twist during animation. The Twists option needs to be enabled before twist links can be used, and the twist links are frozen by default. For example, if you hold your arm out to the side with your palm facing forward, the ulna and radius bones that make up your forearm are actually rotated 90 degrees. NOTE The twist links feature, located at the bottom of the Structure rollouts, cannot be animated individually; it can be used only to deform the skin as the body part is animated. Using Xtras If your character has some other specialized body parts that can’t be covered using the typical Biped structure elements, you can use the Xtras section to add custom structures that are parented to any existing biped part, even to other Xtras. For example, if you’re creating a flying monkey with a tail and wings sticking out from the monkey’s shoulders, Xtras can be used to add the new wings. Each new Xtra added to the biped can have up to 25 links, and you can select the biped object to link the Xtra part to. The Xtras controls, shown in Figure 42.4, also include buttons to automatically select and/or create a symmetrical part. New Xtras are highlighted red and yellow until an opposite is created. Then they become blue and green to match the biped’s left and right sides. New Xtras can be renamed using the name field. FIGURE 42.4 The Xtras section can add new structures attached at any part to the biped. Create Opposite Xtra Delete Xtra Create Xtra Sync Selection Select Symmetrical Pick Parent 1004 55_381304-ch42.qxp 7/7/08 2:24 PM Page 1005 Creating and Animating Bipeds and Crowds Modifying a biped After a biped is created, you may look to the Modify panel to change the biped, but the Modify panel is empty. Don’t be surprised: All the controls for modifying a biped are located in the Motion panel. This is because a biped deals with animation and not just with modifying structures. In the Biped rollout of the Motion panel, you see several icons. These icons are described in Table 42.2. TABLE 42.2 Biped Rollout Buttons Toolbar Button Name Description Figure Mode Enables Figure Mode, where you can edit the skeleton structure Footstep Mode Enables Footstep Mode, where you can animate the biped by placing footsteps to follow Motion Flow Mode Enables Motion Flow Mode, where you can create scripts of motions for a biped to follow Mixer Mode Enables Mixer Mode, where you can load and save Mixer files Biped Playback Plays the animated biped in the viewport in real time showing only the bones Load File Opens .fig, .bip, and .stp files Save File Saves .fig, .bip, and .stp files Convert Converts footstep animation sequences to freeform animation keys Move All Mode Enables a mode where the biped can be moved along with all its animation footsteps The first icon button of a little character is the Figure Mode button. When this button is selected, the button turns light blue, indicating that you are in Figure Mode, and a Structure rollout appears. The Structure rollout includes all the same settings that were available in the Create panel when the biped was first created. In Figure Mode, all bones can be moved, rotated, and scaled as needed to match the required skin mesh. You also need to set the initial position of the biped in Figure mode. If you look closely at the Biped rollout, you’ll notice a title called Modes and Display with a plus sign to its left. If you click this title, several additional buttons appear. The Mode buttons are used to manipulate bones in certain ways and the Display buttons are used to set which biped objects are displayed. The Mode buttons are described in Table 42.3. 1005 42 55_381304-ch42.qxp Part X 7/7/08 2:24 PM Page 1006 Working with Characters TABLE 42.3 Biped Mode Buttons Toolbar Button Name Description Buffer Mode Displays the latest footstep copied into the copy buffer. Rubber Band Mode Allows a parent object to be moved without altering its child hand or foot. Typically results in stretching. Scale Stride Mode Scales the biped’s stride in proportion to the biped’s height. In Place Mode, In Place X Mode, In Place Y Mode Makes the character go through the keyed actions without transforming its center of mass. The second button in the Modes section is used to enable Rubber Band Mode. In this mode, you can move a parent bone without moving its children along with it. For example, if you’ve positioned the left foot exactly where it needs to be, then in Rubber Band Mode, the upper leg can be moved without affecting the foot’s position. This is accomplished by stretching the upper and lower leg bones like a rubber band. NOTE The Buffer Mode, Scale Stride Mode, and In Place Mode all work with animation sequences and are covered later in the chapter. Although most body parts are attached to their adjacent body parts, the head can be moved in Figure mode independent of the rest of the body. This makes creating a headless character easy. Setting the Biped display options The Display buttons in the Biped rollout let you show or hide certain items in order to speed up the display in the viewports. These controls become critical when working with crowds of bipeds. The Display buttons are explained in Table 42.4. TABLE 42.4 Biped Display Buttons Toolbar Button 1006 Name Description Objects, Bones, Bones/Objects Shows only the objects, only the bones (which appear as simple lines), or both