Non Human Character rigging

In this lesson we go even into more details about how the SL Avatar’s Bone System is actually constructed. You might be aware that the Second Life Avatar was originally created with Maya. Thus many of its properties result from how the Maya Animation System was implemented. That’s why we decided to add a small excursion into Maya to better understand the Bone orientations of the SL Avatar within Blender. And since Maya uses the BVH format for its animations we have to take a closer look at this as well.

• A bit of History
• About BVH
• The T-Pose
• Tools Differ
• Maya in More detail
• Proceed to Blender
• Adding a single Bone
• Show Bone Axes in Object Mode
• BVH again …
• The Avastar Trick
• Editing the Bone(s)
• Bone Edit Mode
• Offset and Roll
• Bone Axes in Pose/Edit Mode
• Bone Transform Properties
• Transformations in Edit Mode
• The Bone Data Properties

Bone rolls values are extremely important to let the rig work correctly during animation. Having a clean and consistent bone setup with correct bone roll settings also avoid tedious and sometimes almost impossible fixes.

The correct bone roll settings are also important for animators because one of the major interaction models for transforms is via hotkeys, using the x, y, and z keys to specify axes. And finally a well organized setting of bone roll can make manual animating easier when we use Blender’s pose tools for copy&paste and copy&mirrorpaste.

• The local Y Axis
• The Dominant Axis
• The Lower Arms (Elbow Joints)
• The Lower legs (Knee Joints)
• The Head
• The Eyes
• The Dominant axis and the X-Z Plane
• Enable Axes Display
• Bones with 2 dominant axes
• Which axis to use when ?
• Modify the Bone Roll
• Editing the Avastar Rig
• Adjust the wrist Bone
• Left-Right symmetries
• Create a symmetric Pose
• Fixing Bone roll Asymmetry
• The root Bone
• The COG Bone

After the previous chapters have taken us through a bit of theory and history, now we will proceed with some practical work.
In this lesson we will start with the default Human skeleton and bend it “into” a Horse skeleton. This approach is dictated by the limitations imposed on us by Second Life. We are obliged to reuse the Second Life Avatar’s skeleton as it is. We only are allowed to move the joints around. However we will see that we can get very close to a reasonable Qudruped skeleton that also would work for almost any other quadruped as well.

• Homework first
• Prepare the Model
• Prepare the Armature
• Hide the Avastar shape
• Use Orthographic View
• Advanced: Manual edit & Snap
• From Human to Horse

Now that we have defined our new shape, it’s important to fix the bone rolls. Bone rolls values are extremely important to let the rig work correctly during animation, avoiding tedious and sometimes almost impossible fixes. These values will determine which is the natural bending direction of each single bone in this rig. This is the reason for that long explanation about joint orientations, bvh standard and the in depth discussion of how to setup bone roll: it is what we have to comply with now.

• The anterior Legs (front)
• X Mirror
• Anterior Legs chain
• Recalculate Bone Roll
• Quickfix for flipped X Axis
• Check the Deform Bones
• Adjust the Deform Bones
• More about Snap
• Check the Rest Pose
• Bone Display Style
• Snap Rig to Pose

The last thing to fix is the IK target locations: The IK targets have been fitted to the Avastar human character. But after we changed the Skeleton to a Horse skeleton the IK bones no longer are where they should be. Actually they MUST be placed where the hoofs are, otherwise the animation process would be incomplete:

• Snap IK Bones to Rig
• Manual Process
• The Pole Angle
• Rotation Constraints
• IK Rotation limits
• FK Rotation limits

We’re finally here! The skinning process is what defines how the mesh should deform to follow our skeleton’s movements. It’s the final, most important thing we have to do to be able to upload our newly created character to Second Life. Avastar provides quite a few options to help us in this process, but for the sake of clarity we also describe the manual process.

• Preparation
• Parenting
• Weight Tools
• Workflow Preset “Skin”
• The Vertex Groups Pane
• Vertex Groups in Edit Mode
• Pose changes in Edit Mode
• Weight Display in Edit Mode
• Editing Weights in Edit Mode
• Finding Broken Verts
• Quick Tip for Eyes