“…In the areas of non-photorealistic rendering (NPR) and illustrative visualization, however, abstraction and emphasis techniques have been investigated. Examples include the use of halos for simple line rendering [2,11] or shading [22,37] and volume rendering [5], the use of additional depth cueing by influencing line or shading parameters (e. g., [11]), interactive emphasis techniques (e. g., [27,35,41]), or focus+context techniques (e. g., [13,39]). …”