Moving from animating a 3D bouncing ball to a 3D character rig, from the first time animators perspective seemed a unique combination of slightly intimidating and intriguing at the same time. Nevertheless, after the introduction on Monday and Today’s animating tutorial, the task of making a character move across the screen is much more appealing.
Much like the movement of a bouncing ball in Maya, moving a character rig follows the same strategy – albeit with more controls. The character rig had several controls to work with;
Between 1 and 3 on the Arms
3 on the torso
Between 1 and three on the Legs
And head controls.
The reason for the alternate controls on the arms and legs was due to two different ‘modes’ of movement available; Forward Kinematics (FK) and Inverse Kinematics (IK). Forward Kinematics is very much a hierarchy of movement. An example:
Top of arm > Moves: Top of Arm, Bottom of Arm and Hand
Bottom of arm > Moves: Bottom of Arm and Hand
Hand > Moves: Hand
Both Kinematics designate a particular control as a ‘Parent’ and the rest as the ‘Child’. The Parent’s movements influence that of the child, while the Child’s movement has no influence on the Parents. In the case of Forward Kinematics, the top of the Arm is the Parent in that it has the control over all other areas of the arm, while the bottom of Arm and Hand are the children. Of course this structure can become complicated in more complicated rigs and feature multi-layered levels of Hierarchy. In the case of the ‘FK’ Arm while the top of the Arm controls the bottom, the bottom of the Arm still retains control over the Hand – so even in this basic rig, the rigger has used a multi-layered structure.
Of course for Inverse Kinematics, this logic is flipped on its head. In the IK Arm hierarchy the Parent is in fact the Hand. By moving the Hand, the rest of the arm compensates for the movement – however extreme it is. By using Inverse Kinematics, it can make quickly moving an arm or leg into position very easy, but it has a few issues. The first is the fluidity of the end animation. By moving all areas of an arm at the same time, the animation will likely not be as fluid as the computer will choose the most direct route to the end ‘goal’. This could mean that an arm which is meant to swing naturally into position might simply move diagonally into place.
Another issue with the IK is that the original length of an arm might become distorted to compensate for a particular hand movement. With FK this isn’t a problem as form is maintained at all times.
These pros and cons are not to say that IK is useless, but more that it has to be applied to the right aspects of a rig. For example often FK will be used for arms but IK will be used for legs as the IK animating is much more suited to quick movements of legs.
In addition to these basic areas which can be manipulated, there are levels of detailed movement which can be captured using the Maya software. For example: fingers, foot movement, and facial expressions can all be edited by imputing particular numerical values or by physical moulding the control. This just adds an entirely new level to what can be done with a basic character rig at the lowest level of Maya Control.
Having had around 3 hours on the software to just experiment, I constructed a simple animation, which I will upload later this week. Still, despite this new interest in the medium of 3D animation, it is somewhat restricting to just work with the ‘Moom’ so I will likely still work in 2D for my final piece.
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