Abstract: We present a novel framework for non-photorealistic rendering (NPR) based on view-dependent geometric simplification techniques. Following a common thread in NPR research, we represent the model as a system of particles, which will be rendered as strokes in the final image and which may optionally overlay a polygonal surface. Our primary contribution is the use of a hierarchical view-dependent clustering algorithm to regulate the number and placement of these particles. This algorithm unifies several tasks common in artistic rendering, such as placing strokes, regulating the screen-space density of strokes, and ensuring inter-frame coherence in animated or interactive rendering. View-dependent callback functions determine which particles are rendered and how to render the associated strokes. The resulting framework is interactive and extremely flexible, letting users easily produce and experiment with many different art-based rendering styles.