We present an interactive modeling system for flower composition that supports seamless transformation from an initial sketch to a detailed three-dimensional (3D) model. To begin, the user quickly sketches the overall appearance of the desired model as a collection of two-dimensional (2D) strokes on hierarchical billboards. Then the user iteratively replaces the coarse sketch with a detailed 3D model referring to the initial sketch as a guide. Since a flower model consists of many repetitive components, the system helps the user to reuse 3D components to facilitate the modeling process. The global view of the entire model is always shown in a separate window to visualize how local modifications affect the global appearance. Our system helps the user make appropriate design decisions to keep the model consistent with the initial design, which is difficult in traditional bottom-up plant modeling systems in which the global view only emerges after all of the details are specified. Catego...