CrossShade: shading concept sketches using cross-section curves

We facilitate the creation of 3D-looking shaded production drawings from concept sketches. The key to our approach is a class of commonly used construction curves known as cross-sections, that function as an aid to both sketch creation and viewer understanding of the depicted 3D shape. In particular, intersections of these curves, or cross-hairs, convey valuable 3D information, that viewers compose into a mental model of the overall sketch. We use the artist-drawn cross-sections to automatically infer the 3D normals across the sketch, enabling 3D-like rendering. The technical contribution of our work is twofold. First, we distill artistic guidelines for drawing cross-sections and insights from perception literature to introduce an explicit mathematical formulation of the relationships between cross-section curves and the geometry they aim to convey. We then use these relationships to develop an algorithm for estimating a normal field from cross-section curve networks and other curves...

• Type: Journal
• Year: 2012
• Where: TOG
• Authors: Cloud Shao, Adrien Bousseau, Alla Sheffer, Karan Singh
• Keywords: Communications, Concept Sketches, CR Categories, Cross Hairs, TOG 2012