Pose a Character

Whenever you create a new Avastar character it will initially be displayed with arms pointing horizontally and sideways. And both feet are parallel to each other standing on ground. This pose is called the “T Pose”, apparently because the character forms the shape of the letter “T”. This pose is also the “neutral” pose. That is, the original character mesh was modeled in that pose.

Pose & Bone

The process of “posing” is nothing else than changing the neutral pose of the character by moving the character bones. And that means there must be a way to relate the bones to the mesh. This is where rigging and weighting comes into play.

Targetless IK is enabled by default for a new Avastar character. You can see it in action when you select for example the left wrist bone and move it around (see image):

• Select the (green) bone controller of the left wrist (using the Right Mouse Button).
• Move the bone down as shown on the image (using the “g” keyboard shortcut).

This property of the armature is named “Targetless IK” (Inverse Kinematic), and the set of affected bones is the IK- chain. In our example the chain starts at the wrists and moves up to the Collar bones. Actually Targetless IK is a great and time saving feature. Imagine you needed to pose each bone separately to get your pose done.

But hold on, there is an issue. Take a close look at the left shoulder. When you inspect that area in detail, then you see an ugly distortion near the neck (see image). The pose has bended the mesh back into itself and it ended up intersecting its own surface. This can easily be fixed by rotating the collar bone back a bit and all is well.

IK Chain controller

[PS Showtime url=”/wp-content/uploads/2012/11/auto-ik.jpg”]

When at least one of the currently selected bones is ik enabled, then you find the Targetless IK control panel in the property sidebar of the 3D view. It is in the “Rig Properties” section.

• We have 5 separate IK chains: two for the arms, two for the legs, and one for the Spine up to the head.
• Each chain starts at the outermost bones (wrist, foot bone, skull respectively) and by default moves up to the collars, the Hips and the torso.
• Each chain length can be changed to end at the outermost bone, or all the way up to the COG Bone (that is the Center Of Gravity bone which is located on the Avastar’s backside, just above the Pelvis).

The 3D Manipulator allows to move and rotate bones just by click and drag. In particular i found the Rotate manipulator very handy to quickly adjust bones. In this context the Normal orientation setting makes most sense as it aligns the manipulator always to the selected bone’s orientation and thus the rotation axes are always oriented in a meaningful way regardless of the current Viewport angle and bone angle.

For example you always will rotate the wrist (green circle), wave hands up/down (red circle) and sideways (blue circle) regardless of the parent bones, the object orientation and the viewport angle.

You find the 3D manipulator Settings in the footer of the 3D View.

Pose and Animation

We know (or maybe just guess) that an animation is something dynamic, like a set of changing poses displayed over time. And a pose is something static, where the character does not move.

While this is in principle correct, technically a pose is exactly the same as an animation. Only that the “set of changing poses” contains only one pose which gets replayed in an endless loop.

For the pose all we need to specify is which bones shall be positioned where. So we could just record all bone locations. But practically it is sufficient to only record the changed bones. This recording is done by creating Keyframes in the Timeline

Keyframes & Timeline

The Timeline: is a recording of animation changes over time. Thus whatever movement happens for whichever bone, it is stored in the timeline.

The timeline can be found in the lower part of the default Blender screen. There is also a timeline cursor available, a green vertical line, initially set at position 0 (zero) in the timeline. Note that timelines are always attached to Objects. In our case the timeline is attached to the Avastar character.

A Keyframe: is a set of bones and their transformation data (location, rotation, scales) at a specific point in time. A keyframe does not need to store all character bones. It is sufficient when it stores just the bones which have been modified since the last keyframe.

You may have noticed that i did not pose the head. I did this on purpose! The reason is that the SL animation system allows us to play and mix multiple animation sequences and poses at the same time.

As a rule of thumb each bone that is NOT contained in a specific pose will be free for to be animatable by other poses. For example the head movement is normally controlled by the mouse. But this works only if the head has not been explicitly posed in our character. We will see in a moment how our pose keeps intact while we can move the head and even walk around in SL.