CompuServe Thread

+++++++++ More info on how to use Bones with IK. This is the beginning of a follow to Bones Rules Part 1. Its, very rough, not complete yet, but rather than waiting, I figured some of it might be helpful to few folks right now. ++++++++++++ PART 2. CREATING BASIC POSES FOR MOVEMENT X. <The DEFAULT STATE MUST HAVE SHAPE AND GROUPING STATES DEFINED> to lock the geometry to the orientation of the bones. The Properties are optional but in most cases probably should also be selected. X. Create new poses for your figure by Rotating joints in Pick Group mode around their LOCAL axes this will maintain the hierarchical relationships and allow you to create more realistic poses. X. <Be sure to SAVE your whole objects after creating new state in the Detail Editor> Otherwise the object file you made will not be update with the new states. X. Other Bone states only need GROUPING defined, unless the geometry is also be deformed with morphing to cleanup a joint in an odd position or a different facial expression is being used, then you would need SHAPE defined as well. You don't need to use Bones Update when you crate a new state. This command is principally to allow you to see how the new pose you created will deform the geometry in the Detail editor. X. Use Bones update to see if your pose is correct. Since Bone states technically only need a GROUPING state it isn't always necessary to perform this command. However you won't hurt anything by doing it. X. <Clean up problems wit the joints using a SHAPE state> This is one of the important tricks in getting bones to work well. Sometimes when you bend a limb into an extreme posture the geometry just won't bend correctly around the joint. You will usually see these problems after you perform BONES UPDATE on the object. Just move the few points that are out of wack, and add a SHAPE state to this pose, as well as the GROUPING. Then when you stage animation that uses this pose, morphing will correct problems with the geometry. X. <NEVER use a DEFAULT state in your animation>, because it will not interpolate with other key states. Default states should be reserved for creating a base shape for LOCKED textures and brushes. Get into the habit of making a duplicate pose of the default as your first NEW state, so you can include that pose in you animation when needed. X. <USING INVERSE KINEMATICS> Inverse Kinematics work the opposite of normal hierarchical animation in Imagine. They allow you to grab an extremity like a hand or foot and and pull or place it where you want. The more primitive method of animating hierarchies is called FORWARD KINEMATICS. Inverse Kinematics can be used to pose almost any kind of limb, but where the technique really shines is in spinal articulations. IK allows them to be manipulating like a linked chain. For example, you can grab the end bone in the tail and wag the whole thing. Or grab a figures head and have the neck and upper body follow it around as you put it into a new position, This kind of movement is what gives articulated objects the appearance of intelligence rather that just reproducing movement from rote. Think about the way you move when you want to pick up an object. You don't think about moving you shoulder a little, and then your elbow a little, and then your wrist a little. You just “think'' your hand directly into position, and the rest of the joints follow along as necessary. Or if you turn to look at someone, you don't think about gradually moving each vertebrae in your neck a slight amount going up until you get to the head. You think about moving your head, and the rest of the vertebrae a follow automatically. IK allows you to pose things this way, but you can also use the older FORWARD Kinematics as well to make minor adjustments (Humanoid users please note that these techniques will not work properly until the 3.0/3.1 upgrades are done. IK is difficult to use with the topsy turvy deisgn of Cycle objects.) X. You activate Inverse Kinematics by turning on Constraints and switching to Pick Objects mode. The freeze menu is used to lock the rotation of joints so they move with more correct biomechanics. For example, you would only want a knee to bend in X so set a JOINT LOCK on the knee for Y and Z. This type of lock does not immobilize the joint it simply restricts the way the the joint can rotate. The joint will still move when its child object, (or parent objects in Forward Kinematic mode) is moved. the other Locks in the FREEZE menu allow to Immobilize objects movement COMPLETELY in one or all axes. An object can either have its position locked or its alignment locked. For example if you wanted to make a figure move one foot forward as if taking a step, you would LOCK the POSITION of the foot or toe that is planted, and you would LOCK ALIGNMENT on the Pelvis so the figures upper body doesn't tip over. Then you would Pick the opposite foot (the one that's not locked in position) and pull it out to take step forward. X. Unfortunately the LOCK parameters are not saved with an objects file, so you have to reset them every time you want to load a figure and pose him. But as you work with IK you'll realize that the locks need continuous adjustment as you create different poses. In many instances, you will want to LOCK POSITION on things like shoulders, pelvis, neck to isolate movements of the limbs so they don't effect the overall pose of the body. -Tim