Fundamentals

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Here's a quick run-through of some of the terminology and basics involved with Geometric hierarchy tracking and rigging.

Moving object. Freely moving object (node) that's the basis of SynthEyes's normal object tracking, driven by various automatic or supervised trackers parented to it. One or more meshes can also be parented to a moving object. Cannot be built into hierarchies.

GeoH object. A regular SynthEyes moving object that is configured to use the GeoH solving mode on the solving panel; it is tracked using the GeoH tracking system instead of the regular solver. May have trackers attached for hybrid tracking configurations. Can be the parent of a single child mesh (attaching more than one mesh is an error). Can be built into hierarchies.

Hierarchy. a collection of interrelated moving or GeoH objects that form a tree, ie any object can have one parent and none, as well as one or more child objects. When an object moves, its child objects are carried along (when that frame is retracked!).

Child objects must always be GeoH objects.

Root object. An object that has no parent, and thus no constraints on its motion. A free-flying drone would be a root object, while a hand would be a child object. A root object can be a GeoH object, or a regular moving object for a hybrid setup.

Pivot. The default position of a child object in its parent's coordinate system. For example, in a body hierarchy with the torso as the root, each hip joint would have a pivot position that defines the neutral position of the leg, where all the joint values are zero.

Joint aka Axis aka Channel aka Degree of Freedom . An object has 3 translational joints/axes/channels/degrees of freedom and 3 rotational joints/axes/channels/degrees of freedom, as in usual 3D animation. While both a moving object and a GeoH object have an animated path in world coordinates, only GeoH objects have these six joints etc that describe its position relative to its pivot point, which in turn is relative to its parent object. All six joints are zero at the pivot location, by definition.

Bone. A illustrative graphic that visually shows the hierarchy. There is a bone from each parent to each child; all such bones are associated with the parent.

Deformation vs animating pieces. When an object owns a mesh and one or more child objects that do not own their own meshes, the (properly configured) children will deform the mesh. So a single mesh can be deformed into the desired shape to match the imagery. Alternatively, you can have individual meshes parented to many different levels in the hierarchy. Animating pieces is typically used for objects such as robots, while deformation is used for organic shapes. Note: the Intro version only animates pieces, it cannot deform meshes.

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