Space-Time Surface Simplification and Edgebreaker Compression for 2D Cel Animations

Abstract

Digitized cel animations are typically composed of frames containing a small number of regions; each region contains pixels of the same color and exhibits a significant level of shape coherence through time. To exploit this coherence, we treat the stack of frames as a $3D$ volume and represent the evolution of each region by the bounding surface of the $30$ sub-volume $V$ with constant-time planes. The intersection is generated in real-time with standard graphics hardware through an improved capping (i.e. solid chipping) technique, which correctly handles overlapping facets. We have tested this approach on real and synthetic black&white animations and report compression ratios that improve upon those produced using the MPEG, MRLE, and GZIP compression standards for an equivalent quality result.