Represents a child reference point on the constrained object's hierarchy.
Child references define points on the constrained object (typically child transforms) that the constraint uses as evaluation origins instead of the constrained object itself. This is fundamentally different from ConstraintSource, which specifies external targets to follow.
When child references are set, the constraint solves for the parent transform such that the weighted child reference points align with the constraint target, rather than aligning the parent object directly. For example, in an AimConstraint, the parent rotates so that the specified child point aims at the target, allowing indirect aiming from an offset position. In a ParentConstraint, child references act as anchor points from which offsets are calculated instead of using per-source offsets.
If multiple child references are provided, their positions and rotations are combined using weighted averaging. The weight of each child reference determines its relative influence in this combination.