Modeling with rendering primitives: an interactive non-photorealistic canvas

Non-photorealistic rendering has placed much emphasis on developing algorithms that determine the appearance of renditions. To successfully deploy NPR rendering systems using these algorithms, however, one has to consider how artists, illustrators, or lay people can influence the created renditions. Many systems require a cyclical process of parameter tweaking, rendering, and validation before one is satisfied with the final rendition. We present an interactive NPR canvas in which a user can construct a rendition with pre-rendered primitives and modify these primitives using tools that provide spatially explicit computational assistance. We call this approach modeling with rendering primitives. Our technique has the advantage of algorithmic support for creating NPR renditions but requires neither global parameter adjustments and re-rendering cycles nor attribute changes on individually selected primitives. We demonstrate the applicability of this interaction technique for the creation of painterly rendering, pointillism, and decorative mosaics.