Hedgehog labeling: View management techniques for external labels in 3D space

Annotations of objects in 3D environments are commonly controlled using view management techniques. State-of-the-art view management strategies for external labels operate in 2D image space. This creates problems, because the 2D view of a 3D scene changes over time, and temporal behavior of elements in a 3D scene is not obvious in 2D image space. We propose managing the placement of external labels in 3D object space instead. We use 3D geometric constraints to achieve label placement that fulfills the desired objectives (e.g., avoiding overlapping labels), but also behaves consistently over time as the viewpoint changes. We propose two geometric constraints: a 3D pole constraint, where labels move along a 3D pole sticking out from the annotated object, and a plane constraint, where labels move in a dominant plane in the world. This formulation is compatible with standard optimization approaches for labeling, but overcomes the lack of temporal coherence.