Abstract:
This paper presents a hatching algorithm which -- while also allows for an implementation in real-time -- is integrated into the production pipeline of computer generated motion picture. Motion picture production pipelines impose special functional and quality requirements. From the functional point of view, the stages of modeling, 3D rendering, and compositing form a pipeline without feed-back, and frames are rendered independently, possibly on different computers. Thus, no temporal data can be shared between them while flicker free animation needs to be generated. Quality requirements can be grasped as that of dual consistency: the generated hatching must consistently follow object movement and deformation, and, at the same time, it should have a consistent pattern and density in image-space to provide the hand-crafted look. In order to meet both requirements, we apply a particle based method and develop an image-space density control mechanism using rejection sampling and low-discrepancy sequences. We also discuss the decomposition of rendering tasks according to the main stages of the production pipeline and demonstrate how the artist can define the illustration style in a convenient way.
Keywords:
NPR, Hatching, rejection sampling, Halton series, animation.