Essential Blender- P14 docx

Figure RST.28: The toe bone sized and in place. Go back to an angled view and select the root of the "toe_L" bone. In a side view, Ctrl-LMB click once behind the tip of the lower leg bone, then once again a little further back. Figure RST.29: More foot bones. Select the joint between the last bone created and the one just before it. Press Shift-S again to bring up the Snap menu and choose "Selection to Cursor." The 3D cursor should still be at the tip of the lower leg bone, snapping the new bones' joint to the same place. If you've accidentally moved the 3D cursor by LMB clicking in the 3D view at some point, you will have to reset it by selecting the tip of the lower leg bone and using "Cursor to Selection." The bones on the other side of the armature should follow along, giving you this: Figure RST.30: The rest of the foot bones in place, and named appropriately. Name the new bones "foot_L/R" and "ankle_L/R" to match the illustration. Creating Parent/Child Relationships in the Feet You want the feet and legs to move at the request of the controller bone. You'll get to the legs in a moment, but you can get by with only parent/child relationships for the feet. Select the "foot_L" bone and Shift-RMB select the "leg.control_L" bone. Press Ctrl-P to make the leg controller the parent of the foot bone. When you make a parent/child relationship with bones, there is one more step than when doing it with regular objects. Upon pressing Ctrl-P, a menu pops up asking "Connected" or "Keep Offset." You've gone to some small trouble to offset the bones in just this way, so choose "Keep Offset." Now, RMB select "toe_L" and Shift-RMB select the left leg's controller again. Ctrl-P to make it the toe's parent, choosing "Keep Offset." Repeat this procedure on the other side of the armature. At this point, you have almost all the bones you need to control Hank. The next step will involve adding some constraints, which must be done in Pose mode. Before you temporarily leave Edit mode, though, there is one more thing to do. Fixing Bone Roll Remember how you removed the rotation and scaling from the Hank mesh before you began this whole procedure? The same thing needs to be done to the bones before you start constraining and animating. With the armature still in Edit mode, use the A-key (once or twice, depending on what you currently have selected) to select all the bones in the armature. Press Ctrl-N and accept the pop-up that appears. Several of the bones, particularly the ones in the arms and legs, roll in place. Figure RST.31,.32: Before and after recalculating bone roll. What you've just done is recalculated optimized roll values for all the bones. This will make animating significantly more predictable. With that accomplished, leave Edit mode for a while and see how the armature moves. Making the Legs Into I K C hains Armatures can work in three different modes: Edit, Object and Pose. The Tab-key toggles into and out of Edit mode. Ctrl-Tab toggles between Object and Pose modes. Edit mode overrides both Object and Pose modes, so pressing the Tab-key in either mode will take you to Edit mode. Determining Edit, Object and Pose mode for armatures. At first, determining what mode your armature is in can be a bit confusing. When all bones are selected, their selection outlines are: - Yellow for Edit mode; - Blue for Pose mode; and - Pink for Object mode. If you still can't figure it out, you can use the pop-up menu on the 3D header to see which mode your armature is in, and to change the mode. Figure RST.33: The Mode menu on the 3D header. Press the Tab-key to go from Edit mode to Object mode. Then, press Ctrl-Tab to put the armature into Pose mode. Hank's legs, like the legs of most armatures, will be rigged with Inverse Kinematics, meaning that the leg bones are not posed individually, but by moving a target bone and forcing the legs to follow. In an angled view, RMB select the bone "ankle_L" and Shift-RMB select "leg.lower_L," in that order. Notice that in Pose mode, selected bones are outlined in bright blue. Press Ctrl-I, the hotkey for adding an IK constraint. Accept the "To Active Bone" popup that appears. The leg bone should turn a dull yellow. In the buttons window at the right, you will see an IK Solver constraint in the Constraints panel. Figure RST.34: The left leg made into an IK chain. Now, to see how this works, RMB select the controller for the left leg and foot, "leg.control_L," and move it around with the G-key. The leg follows the foot, mostly. Now, try some rotations to see how the foot and leg react. To work with rotations when posing bones, it is quite efficient to turn on the rotation Transformation Manipulator. By no means do you have to use it, but many animators find that it significantly speeds up their work flow. Use Ctrl-Spacebar in the 3D view to select "Rotate" from the Manipulator pop-up menu. On the 3D header, make sure that the Alternate Transformation Space is set to "Normal," which will cause the manipulator to operate locally on each selected bone. Figure RST.35: The rotation manipulator, set to Normal space. With the LMB, click and drag on the different orbits of the rotation manipulator to see how the leg and foot react to rotations of the controller. When you are done playing around, make sure to use Alt-R and Alt-G to clear any transformations you've put onto the bones. One thing you may have noticed is that when rotating the controller around the Z Axis (the blue orbit), the foot turned, but the leg did not follow. This is because IK solving involves the position, not the rotation of the target object. When the controller rotates, the target barely moves; likewise, the leg. Unfortunately, using the "Rot" button on the IK constraint controls does not do the trick. In order to get the leg to rotate along the Z axis with the controller, you need to add a new bone. Of course, bones can only be added and removed in Edit mode, so back you must go! Before switching to Edit mode, RMB select the lower leg bone. Then, use the Tab-key to enter Edit mode. You'll notice that the same bone is automatically selected in Edit mode. Edit mode and Pose mode selections carry over into one another, making it convenient when you are troubleshooting a rig like this. Adding a Loc k T rac k Constraint for the K nee You don't necessarily want to have the entire leg chain rotate with the foot. In general, it will be the knee that rotates to keep pace with the foot's direction. If you get up and walk in a circle for a while, you will probably observe that, while the foot can rotate independently of the knee a little, the knee usually follows, a little behind. You can mimic that same behavior by creating a new bone and adding a constraint. With the lower leg bone selected, go into a side view. Press Shift-D to duplicate the bone and move it forward, away from Hank. Rename this bone "knee_L." Then, scale the bone down until it looks something like this (be sure to scale the bone here, not just grab the root or tip and make it smaller that way. It's fairly important that the bone maintain the same angle and direction as the lower leg bone): Figure RST.36: A new bone called "knee_L." As you can see from the dashed line, the knee bone is the child of the upper leg bone. You want it to actually be the child of the leg's controller. So, as the knee bone is already selected, Shift-RMB select the controller ("leg.control_L"), and use Ctrl-P to create a parent/child relationship using "Keep Offset." Press the Tab-key to leave Edit mode. It should have returned you to Pose mode, as that's where you were before. If not, though, use Ctrl-Tab to re-enter Pose mode. Now, let's add the Locked Track constraint. The easiest way to do this is to first RMB select the knee bone, then Shift-RMB select the lower leg bone. With the mouse still over the 3D view, press Ctrl-Alt-C, which will bring up a list of different available constraints. Choose "Locked Track" and watch your leg bones go kerblooey. Note: You can always add and configure constraints by using the Constraints panel in the Edit buttons. However, doing it from the GUI saves you from having to enter the names of the target armature and bones. Locked Track is one of the less-understood constraints. It is like a version of the Track To constraint, whose behavior is obvious, that allows you to prevent the tracking along one axis. So, if you were to prevent the bone from following its tracked target along the Y axis, its length, the bone would rotate only around its length as it followed the target. That is what you would like the leg bones to do. So, in the Locked Track constraint on the Constraints panel, set the "Lock" control to "Y," so the bone will only roll around its length. But which value to click for the "To" control? If you were to show the Axes for each bone ("Draw Axes" on the Armature panel), you would see that the lower leg bone's Z-axis is the one most closely pointing toward the knee bone. So, in the Locked Track controls, set "To" to "Z." If the Z axis had been pointing away from the knee, the best choice would have been "-Z." When you adjust Lock to Y and To to Z, the leg regains its normal behavior, but with an addition. Now, selecting the controller bone and rotating with the blue orbit (Z axis) rotates the lower leg bone as well. To get the upper leg to follow, repeat the Locked Track procedure: - Select the knee bone first, then the upper leg bone; - Ctrl-Alt-C and choose "Locked Track"; and - Adjust the constraint so that "Lock" is Y and "To" is Z. The next step is for you to repeat this entire portion of the exercise for the right leg. Here's a brief rundown, so you can keep track of what you're doing: - Create an IK solver on the lower leg, targeting the ankle bone; - Duplicate, scale and move the lower leg bone in Edit mode to create the knee bone; - Change the knee bone's parent to the right leg's controller; and - Add Locked Track constraints to the upper and lower legs, targeting the knee bone. Figure RST.37: The legs and feet with knee targets and IK in place. Restricting T ransformations So you have a leg and foot rig that works reasonably well. But what happens if you (or someone else) grabs one of the foot or knee bones and translates them? Then the rig is ruined. There is a simple way to prevent this. In Pose mode, make sure that the Transform Properties panel is active. If it isn't, press the N- key to bring it up.