A critical problem of movie rendering is that while frames are calculated independently, the image sequence should not present flickering or inconsistency. A piece of curve must be consistent with the 3D geometry and move and deform with the object. On the other hand, it must also be consistent with the 2D image since in the traditional drawing process the artist draws in 2D. Hand drawn lines are roughly independent of the distance of the object from the viewer since rendering happens directly on the paper. Finally, manual drawing involves a great deal of randomness - the artist is not able to draw the same line twice. Being synchronized in both object and also in image spaces seems to be contradicting requirements. The rendering process should resolve this contradiction while presenting the natural randomness inherent in manual work. This paper presented an NPR (Non-Photorealistic Rendering) system and its application in the movie rendering pipeline. Our system implements three NPR effects: contouring, hatching, and painterly rendering. The algorithms that have been developed guarantee that these effects remain consistent with the animation and the deformation of the 3D geometry, avoid flickering, while still maintaining the look of hand drawn images. This project also proves that NPR effects can be made flexible enough to allow the artist to express his/her own ideas and produce images meeting his/her expectations
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