Computer-generated mosaic animation

As a new attempt for Non-Photorealistic Rendering and Animation, we extend computer generated mosaic techniques to produce animations and explore its visual possibilities. While simulating a 2D cel cartoon effect, we aim to minimize “popping” and maintain temporal coherence. Our solution includes four major components.; A “layer” concept is first introduced to separate different objects into layers. This allows us to isolate objects' influence from the nearby tiles due to their changing shapes.; A physically based model is then used to move the tiles inside an object when the object changes its shape. A spring-like connection is set up among tiles and the control points along the border of an object. Tiles displace to their new positions when all the forces achieve equilibrium. The parameters of the forces give us control on the way tiles move.; A neighbourhood relations among tiles are maintained by Delaunay triangulation. The resulting mesh allows us to detect the densities in different regions. A edge-based scheme is proposed to create new tiles where the space is too sparse and merge or delete tiles where the space is too dense.; We also give tiles the freedom of varying their sizes, thus making the animation evolve more smoothly. Multiplicatively weighted Voronoi diagrams, which allow Voronoi regions to vary their sizes with their corresponding tiles, are employed in the relaxation algorithm to locate the new positions of the tiles.; A prototype of the system is implemented. While giving users enough flexibility on making a frame of mosaic image, it minimizes users' interaction on producing animation. The result matches well with our visual goal.