Abstract: We present an interface for collaborative conceptual design that combines sketch elements, direct manipulation of 3D objects and non-photorealistic rendering. Such a combination results in a simple and intuitive 2D-sketch-to- 3D modeling system suitable for novice users. It allows users potentially located in geographically distant areas to cooperate by sketching, exploring and modifying their ideas interactively, with immediate visual feedback. Our system prototype supports several modeling primitives and can be extended to handle user-defined objects. Potential applications of our system include early stages of urban and landscape design, rapid prototype of virtual environments, animation, education and recreational use.