Inverse Kinematics :
If you have no intention of using and/or learning about IK Solvers, then you can skip straight to the Skinning part of this tutorial. For those of you who are wiser than those thinking about skipping, lets continue.
Inverse Kinematics, by name... are the 'Inverse' of Forward Kinematics. Forward kinematics would be what we did to pose the character after linking, In order to lower the hand, we had to rotate the shoulder, then the arm, the wrist etc. Inverse kinematics are the other way round, if you want to lower the hand... you'd grab the hand, and lower it... everything else in the Solver will follow it accordingly, dependant on your pivot points and where you're positioning the IK Solver.
IK Solvers are a nice and easy way of animating multiple objects with just one controller. But it's entirely based on the joints in your model, so if your pivot points are illogically placed, you're going to get some very strange problems. See this example:
 |
The above example shows my characters arms in 2 scenarios. One modeled already bent, and the other straight, or awkwardly positioned. The IK Solver on the 'Right' side is able to work out which way to move the mesh based on the pivot points of the beginning, end and all in between. If you look at the 'Wrong' example, where the pivots actually go in a zig-zag fashion, the IK Solver has no idea what I want to do with this mesh, and clearly calculates that I really want to break my characters arm. This happens because IK Solvers have a 'Preferred Angle' that it tries to find when one is applied, on the 'Right' image, the angle is clear, thus meaning the calculation for the IK is clear. On the 'Wrong' image, it's all messed up, and so is the calculation.
You will find IK Solvers in the Animation menu, under the title 'IK Solvers'. The most basic Solver of them all is the IK Limb Solver, and as you can guess... it's designed purely for limbs, for example... Bone Mesh with 3 steps in it, Top – Middle – Bottom . Or, Thigh – Knee – Ankle (They're close enough):
 |
In most cases, you would only need 4 IK Solvers, two for each of the leg movements, and 2 more for the arm movements. Seeing as how my character has more than 3 steps in his arms (6 steps from Shoulder to Palm), the IK Limb solver is of no use to me here, instead I will use the HI Solver. The HI Solver is a lot like the IK Limb Solver, in that it manipulates the objects based on the preferred angle of the start and end points, the difference between the two is that the HI Solver can handle a lot more steps than the IK Limb solver. When applying an IK Solver, you need only select the start mesh, then drag the cursor to your end mesh and select it. Remember that whatever mesh you end it with, will be the controller.
I will only be using these 4 IK Solvers, so that concludes the Inverse Kinematic section of this tutorial. Next up, "would be" the Reaction Manager page, but I sort of ballsed it up. In practice, I applied my Spline Controllers AFTER the reaction manager, which meant having to do the Reaction Manager process all over again... SO, next up, is Spline Controllers And Constraints.
