In radiation therapy treatment planning, physicians need to understand the three-dimensional distribution of radiation dose in the fullest possible context of the patient anatomy.   There are typically many superimposed surfaces in this data whose 3D shapes and locations must be understood in relation to each other.   To facilitate an immediate understanding of the 3D location of the relevant soft tissue structures indicated by the skin surface, without unduly obscuring the visibility of the underlying tumor and dose surface, I developed a method for automatically highlighting the locations of the valley and ridge lines that are central to the understanding of the surface shape.   This research is described in the paper: Interrante, Fuchs and Pizer. "Enhancing Transparent Skin Surfaces with Ridge and Valley Lines", proc. Visualization '95, pp. 52-59 (728k pdf).