Dynamic Annotation of Interactive Environments using Object-Integrated Billboards

We present a technique for the dynamic annotation of three-dimensional objects in interactive virtual environments. Annotations represent textual or symbolic descriptions providing explanatory or thematic information associated with scene objects. In contrast to techniques that treat annotations as two-dimensional view-plane elements, our technique models annotations as separate three-dimensional scene elements that are automatically positioned and oriented according to the shape of the referenced object. The shape of such an object is generalized by an annotation hull and skeleton used to determine an adequate position and orientation of the annotation with respect to the viewing direction. During camera movements, annotations float along the surface of the annotation hull. Additional constraints for the generalizations provide further control about geometric and dynamical properties. In a case study, we show how this technique can be applied for annotating buildings and other components of virtual 3D city models.