Animating Real- Time Game Characters-P5

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Animating Real- Time Game Characters-P5

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Animating Real- Time Game Characters-P5: My intent in writing Animating Real-Time Game Characters has been to share my work methods, thoughts, and ideas about animating real-time characters in 3ds max 4™ and character studio 3®. Any factor that affects the animation process using these two tools has been covered.

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  1. 108 Animating Real-Time Game Characters FIGURE 3.24 The Initial Skeletal Pose option helps you go from an animated to unanimated state. FIGURE 3.25 Assign all the upper arm vertices to the UpperArm link. (think knee and thigh). Vertices that are farther above the elbow will be less influenced by the forearm, and vertices below the elbow will be less influenced by the upper arm.
  2. Chapter 3 Weighting a Character Using Manual Vertex Assignment 109 Whenever it's a certainty that two links will be influencing a set of vertices like the elbow, go ahead and assign them all an equal weighting (1 to the parent link and 1 to the child link). Of course, these values won't stay that way for all the vertices, but it's a quick way to assign them to the right links simultaneously, causing the default Currently Assigned Links Only to be a boon and not a handicap when tweaking the values. Zoom in on the elbow area, and only select those vertices that make up the elbow. Bring up the Type-In Weights dialog box, click All Links, and assign the vertices to Betty R Forearm by clicking on it and typing in 1 (the vertices will turn dark green). Toggle Initial Skeletal Pose back and forth by unchecking and checking its box to see the effects the weighting change has on the elbow (Figure 3.26). FIGURE 3.26 The elbow here has equal influence on both the UpperArm and Forearm links. Unfortunately, the Forearm link does not immediately follow the UpperArm link in the Type-In Weights dialog box. Several links that are children to the Forearm appear first. Be careful not to accidentally assign weighting to a Hand link when you think you're assigning it to the Forearm (Figure 3.27)! While the weighting doesn't look bad, giving all of the vertices equal influence from both links detracts from the intent of the geometry, which
  3. 110 Animating Real-Time Game Characters FIGURE3.27 Beware the confusing out-of-order Forearm link. is to portray a thick elbow pad. Therefore, a few adjustments need to be made. By toggling the Initial Skeletal Pose box on and off, you can get a rough feel for what the values of the vertices should be changed to. For example, the vertices at the top of the elbow need to be influenced less by the forearm so the elbow can retain more of its shape, but the vertices at the bottom of the elbow don't need to be changed as much. Turn your Initial Skeletal Pose back on, and try the values shown in Figure 3.28 for the elbow area. Now when the elbow is bent, it looks better and keeps the shape of the elbow pad intact. (Figure 3.29). That solution solves the problem with the back of the elbow, but the front of the joint (the bottom of the bicep area) needs to be tweaked as well. With a weighting of 1 and 1, the arm crimps enough to make the bleep shrink, instead of remaining the same or bulging. However, if you bias the vertices more toward the UpperArm link, the forearm geometry will look strange (Figure 3.30). A solution to the forearm deforming the way it does is to lessen the contrast of the elbow juncture; transfer some of the influence from the forearm vertices over to the UpperArm link. It doesn't have to be much, and can vary from character to character. Select the three vertices at the top of Betty's arm in the bent position, lock them, and add the Betty R UpperArm link to the links that influence the vertices. A value of 0.1 should work fine (Figure 3.31).
  4. Chapter 3 Weighting a Character Using Manual Vertex Assignment 111 FIGURE 3.28 The elbow needs to be biased more toward the UpperArm link. FIGURE 3.29 The elbow looks better with the new weighting values.
  5. 112 Animating Real-Time Game Characters FIGURE3.30 Biasing the front of the elbow joint to the UpperArm link causes a strange deformation. FIGURE 3.31 Adding the UpperArm link to links that influence these vertices helps deform the forearm better.
  6. Chapter 3 Weighting a Character Using Manual Vertex Assignment 113 This juggling of weighting influence between adjoining links is neces- sary to get around the limitation, which is a drawback of most generic weighting algorithms found in most programs like Physique. Only with a true "sliding skin" weighting system can areas like elbows, knees, wrists, ankles, necks, and even shoulders and hips be 100 percent accurate in the deformation of polygonal skin. However, keep in mind that this only applies to real-time games; movies featuring CG-rendered characters em- ploy all kinds of complex skeletal and musculature algorithms to simulate skin and muscle movement. Working on the Hand and Fingers While most real-time game characters have mitts for fingers and clubs for fists, Betty has the full use of five digits on her right hand. The weighting for wrists is somewhat similar to that for ankles; select the vertices at the joint, and give them equal influence by both Forearms and any of the in- ternal Hand links. To avoid too extreme a deformation at the wrist area, sometimes it's a good idea to build your character with the palms facing forward instead of downward. This may be as simple as turning the hand geometry, and then turning any bad edges (Figure 3.32). The fingers need to share influence between links at the knuckles. Starting at the end link of the finger, and working your way towards the FIGURE 3.32 Sometimes it's the geometry rather than the weighting that needs to be tweaked to ensure proper deformation.
  7. 114 Animating Real-Time Game Characters hand, select and assign the vertices to each link along the way (including all knuckle vertices), locking them as you go (Figure 3.33). FIGURE 3.33 Assign the vertices of the hand by starting with the fingers. As you can see in Figure 3.33, the vertices highlighted in Group 1 are assigned to Link A. Vertices in Group B are assigned to Link B, and those in Group 3 are assigned to Link C. The quickest and easiest way to com- plete the weighting is to go back and select only the knuckle vertices, and share influence with the link that is the parent of the assigned link. Whenever the Type-In Weights dialog box is brought up and All Links is chosen, the link to which the selected vertices are assigned will automatically be high- lighted, to make it easier to see against all the other links. However, when the link selected is far enough down the overall list, character studio displays it by dropping it to the bottom of the display window. By assigning vertices to the end link of the fingers, and moving inwards towards the parent, the parent link that needs to share influence over the vertices selected will be visible and on top of the selected link when the list of links is displayed. If the vertices had been assigned to the par- ent first, the child would be below the displayed list, and you would have to scroll down to see the child of the selected link (Figure 3.34).
  8. Chapter 3 Weighting a Character Using Manual Vertex Assignment 115 FIGURE 3.34 When typing in values for a parent-child set of links, assign the vertices to the child first, not the parent. Character studio duplicates the naming of links so that each character can have a number of Hand links. The best way to tell them apart is to look below each link in the list of links. For Betty's uppermost knuckles, share influence with the Hand link above the link the vertices have been assigned to. Often, when weighting vertices by hand, you 'II select a set, enter their values with the proper links, and then select another set, keeping the Type-in Weights dialog box open all the while. One quick way to isolate a link when "offscreen" is to toggle back and forth between displaying All Links and Currently Assigned Links Only. Doing this immediately lines up the selected vertices' link at the bottom of the long list and saves you from scrolling up or down to find it. For the thumb, rotate your view so you can see it in profile, and se- lect and assign its vertices (Figure 3.35). All the vertices in Group 1 are assigned to Link A, Group 2 to Link B, and Group 3 to Link D. Share influence with the proper links, and the thumb is weighted. The vertices in Group 3 that are assigned to the Betty
  9. 116 Animating Real-Time Game Characters FIGURE 3.35 The thumb is a little different from the fingers, but you assign the vertices in the same way. Hand link (Link D) can share influence with Betty R FingerO (Link C). Un- hide all the Biped Finger objects of the right hand to test the weighting. Saving Your Weighting Values Most of the time, the best way to save your weighting values is to save it- erative versions of your mesh as you work. You can also easily reuse or recover your weighting by saving the .phy file. Do this by clicking on the Save Physique (*.phy) File icon (Figure 3.36). FIGURE3.36 Save your Physique file for additional insurance or later reference.
  10. Chapter 3 Weighting a Character Using Manual Vertex Assignment 117 Keep in mind that when re-loading a physique file into one character or another, the Biped structure has to be the same, with the same added bones (if any) assigned to it. When working with older Biped or 3ds max files, Biped will sometimes revert to the previous version of character studio's naming convention. This means that all Biped links will be named after their child (one link below) instead of the actual bone they correspond to. Assigning the Neck, Shoulders, and Torso Hide m_headarmleg, and unhide m_torso, m_energy, m_fanvent, and all the Biped Spine objects, and go to the Right viewport (Figure 3.37). FIGURE 3.37 Even torso mesh objects are supposed to be heavily armored (that is, rigid). Start with the neck. Since the head is a separate object, it's easier to weight both it and the neck. When the neck is joined to the head, it re- quires more polygons and more time to set up the weighting. Zoom in to the top of the neck, select the vertices there, and assign them to the Betty Head link. Unhide the Biped head and m_headarmleg to test the deformation (Figure 3.38).
  11. 118 Animating Real-Time Game Characters FIGURE 3.38 The top of the neck is linked solely to the head to avoid making the gap there visible. Since there's no geometry at the top of the neck, the line of vertices there has to move with the head. Now, undo any rotations you did, and re-hide m_headarmleg and Betty Head. Hide the assigned neck vertices, go to the Front viewport, and select all the vertices near her right shoul- der geometry. Don't include any of the rear backpack geometry (for ex- ample, m_fanvent or m_energy), but assign them instead to the Betty R Clavicle link (Figure 3.39). Linking the shoulder to the clavicle gives you a small amount of mo- bility, but because Betty is supposed to be wearing heavy armor, the shoulder will remain almost motionless throughout her animations. Hide those assigned vertices, and go back to the Right viewport. Make sure all three of the mesh objects are selected (m_energy, m_fanvent, and m_torso), and assign the vertices of the backpack and upper torso to the Betty Spine2 link (Figure 3.40). All the vertices are assigned to the second spine link instead of par- tially to the third, because the backpack and upper body armor need to appear hard and inflexible. Assigning as many vertices as possible to one link achieves this look. However, because there are four links, some of the lower backpack and torso vertices can be assigned to Spinel, the par- ent of Spine2 (Figure 3.41).
  12. Chapter 3 Weighting a Character Using Manual Vertex Assignment 119 \ I I I FIGURE 3.39 Assign the shoulder pad vertices (1) to the Betty R Clavicle link (A). FIGURE 3.40 The backpack and upper torso vertices (2) are assigned to the Spine2 link (B).
  13. 120 Animating Real-Time Game Characters FIGURE 3.41 The vertices in vertex Group 3 are assigned to Link C, the Spinel link. Earlier, Spine2 was chosen as a link for the backpack vertices, because Spinel would have vertices assigned to it as well, and Spine2 was a better choice over Spine3 due to its proximity to the next bone in the hierarchy. Next, the vertices near the waist need to be tweaked further, to make sure they deform smoothly when the torso bends and twists. Select only the vertices that make up the two rows you just assigned to Spinel, bring up your Type-In Weights menu, and assign the vertices to the Betty Spine link as well. Make sure you don't assign any backpack vertices to the second link (Figure 3.42). Weighting the Other Leg Assign the vertices of the right leg to their proper link by referencing the first leg you spent time weighting. First, assign the Toe vertices of the leg element of m_torso to the Toe link, and hide them. Then unhide m_headarmleg, and go to the Front viewport. Select both m_torso and m_headarmleg. Click on the Select by Link button on the Vertex menu to the right (Figure 3.43). Click on the left Foot link and study the vertices selected (Figure 3.44, page 122).
  14. Chapter 3 Weighting a Character Using Manual Vertex Assignment 121 FIGURE 3.42 Giving the waist vertices influence from both Spine! and Spine ensures smooth deformation. FIGURE 3.43 The Select by Link button selects all vertices assigned to a link. Using Select by Link is a quick way to see which vertices you previ- ously assigned and how. Because of the pose of the Biped rig, some of the vertices of the right foot geometry are included in the vertices assigned to the left Foot link. Ignoring this temporary weighting, select all the ver- tices of the right foot geometry that mirror the left foot geometry. Assign them to the Betty R Foot link; then, using the left foot vertices as a guide, type in matching values for the right foot vertices (Figure 3.45).
  15. 122 Animating Real-Time Game Characters FIGURE 3.44 Selecting the left Foot link to see which vertices are assigned to it also selects some vertices of the right foot geometry. FIGURE 3.45 Using the vertices of one foot for reference, the other one is easily and quickly weighted.
  16. Chapter 3 Weighting a Character Using Manual Vertex Assignment 123 Use this same technique to weight the right knee and rest of the right leg geometry. When you get up to the thigh area, hide m_headarmleg, and make sure to assign the left thigh vertices to the Betty L Thigh link (Figure 3.46). FIGURE 3.46 Don't forget to assign the left thigh vertices to the L Thigh link. Loading a .Bip File into Biped Before moving on to weight the hips, you need to apply a run animation to the character to see the effects of the weighting as you make adjust- ments. The rest of the character could have benefited from a full anima- tion as well, but for the hips, it's especially important to see the character's mesh deform while adjusting it. A run or walk animation is perfect for this. Hide everything but Betty Spine and m_torso. Select Betty Spine, and go over to the Biped menu on the Motion panel. Make sure you're out of Figure mode. Click on the In Place Mode icon (it turns purple). Now the character will stay in view, even if the animation translates it through space and it's supposed to move off-screen. This mode is great for fine- tuning animations for real-time characters, which, by nature, usually need to be animated "in place" for implementation in a game. Click on the Load File icon (Figure 3.47).
  17. 124 Animating Real-Time Game Characters FIGURE3.47 Click on the yellow Open File icon to load a .bip animation into your character. Find Run.bip in the Chapter3 directory on this book's CD-ROM, and load it into your character's Biped. Click on the Time Configuration icon located near the bottom of the screen to the right (Figure 3.48). FIGURE 3.48 The Time Configuration icon brings up the menu that controls the number of frames displayed. Once the Time Configuration menu comes up, establish the number of frames in the active animation range by setting the Start Time to 0 and End Time to 18 (Figure 3.49). Changing the length of the animation to match Run.bip allows you to play it in an endless loop if you want. Hit OK, and as you slide the Time Slider or advance through the animation frames, the mesh deforms with the run animation. Advance forward through the animation one frame at a time by hitting the period (.) key. Go back a frame at a time by hitting the comma (,) key. Play and stop the animation by hitting the slash (/) key.
  18. Chapter 3 Weighting a Character Using Manual Vertex Assignment 125 FIGURE 3.49 Set the animation Start and End time to 19 frames (0-18). With the animation applied to the Biped, you will find it easier to see the deformation on all parts of the mesh. With the In Place mode active, the character won't run away as you try to weight it. The In Place Mode icon has a fly-out menu that allows you to restrict the movement along the X-axis only, Y-axis only, or both simultaneously (the default). Just hold down the mouse button with the cursor over the icon, and drag down to bring up the other options (Figure 3.50). Tackling the Hips The hips are one of the most difficult areas to weight, second only to the shoulders. Usually, even when weighting vertices manually, it's a good idea to see how closely the default initialization weighted the hips before dialing them in by hand. Put Betty in her Initial Skeletal Pose, and select all the vertices around her hips. Click the Remove from Link button to make it active, go to the Front viewport, and drag your selection fence across all the links on either arm.
  19. 126 Animating Real-Time Game Characters FIGURE 3.50 These are the options for the In Place Mode icon's fly-out menu. Whenever you use Remove from Link, you must select the right type of three avail- able vertices. Since you 're dealing solely with rigid vertices, make the green plus sign active, or the removal won't take. Also, under the Blending Between Links menu, choose No Blending (Figure 3.51). FIGURE 3.51 Under Vertex Type, select the color of the vertices to which you're applying Remove from Link. Drag the selection fence across the upper body Spine links, as well. Lock the vertices, and play or frame forward through the animation. The front part of the hips look good, and the posterior looks nice except for the bottom two rows of vertices of her rear. When Betty takes a step, you can see those vertices have too much weight assigned to the leg links, so they need to be corrected. Turn on the Initial Skeletal Pose again, and, on Betty's right buttock, select the nine vertices shown in Figure 3.52. Unlock them, and assign them a weight of 1 for both the Betty R Thigh link and the Spine link that appears just above it in the Type-In Weights dialog box (Figure 3.52).
  20. Chapter 3 Weighting a Character Using Manual Vertex Assignment 127 FIGURE 3.52 Assign these vertices an equal weighting value for both the Thigh link and Spine link above it. If you had not checked Triangle Pelvis under the Structure sub-menu on the Biped rig, you wouldn 't have the two additional Spine links to help hold the hips together (Figure 3.53). As you'll see later, these two Spine links will often supplant the Pelvis link—if not replace it entirely—to hold the hip shape together. FIGURE 3.53 The Triangle Pelvis checkbox is pretty useful after all. Turn off Initial Skeletal Pose again, and see how the area deforms. Everything should look good now, except for the three vertices above the ones just corrected. Select these three, unlock them, and assign them to the Spine link above the Thigh link (Figure 3.54).
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