Shadows for cel animation

ABSTRACT

We present a semi-automatic method for creating shadow mattes in cel animation. In conventional cel animation, shadows are drawn by hand, in order to provide visual cues about the spatial relationships and forms of characters in the scene. Our system creates shadow mattes based on hand-drawn characters, given high-level guidance from the user about depths of various objects. The method employs a scheme for “inflating” a 3D figure based on hand-drawn art. It provides simple tools for adjusting object depths, coupled with an intuitive interface by which the user specifies object shapes and relative positions in a scene. Our system obviates the tedium of drawing shadow mattes by hand, and provides control over complex shadows falling over interesting shapes.

REFERENCES

• 1: Wagner Toledo Corrêa , Robert J. Jensen , Craig E. Thayer , Adam Finkelstein, Texture mapping for cel animation, Proceedings of the 25th annual conference on Computer graphics and interactive techniques, p.435-446, July 1998 [doi>10.1145/280814.280949]
• 2: Jean-Daniel Fekete , Érick Bizouarn , Éric Cournarie , Thierry Galas , Frédéric Taillefer, TicTacToon: a paperless system for professional 2D animation, Proceedings of the 22nd annual conference on Computer graphics and interactive techniques, p.79-90, September 1995 [doi>10.1145/218380.218417]
• 3: GORNOWlCZ, G., AND WILLIAMS, L. Snap to it! Automatic 3D object and silhouette registration. Sketches and Applications, SIGGRAPH 2000.
• 4: Takeo Igarashi , Satoshi Matsuoka , Hidehiko Tanaka, Teddy: a sketching interface for 3D freeform design, Proceedings of the 26th annual conference on Computer graphics and interactive techniques, p.409-416, July 1999 [doi>10.1145/311535.311602]
• 5: KERSTEN, D., MAMASSIAN, P., AND KNILL, D. C. Moving cast shadows induce apparent motion in depth. Perception 26, 2 (1997), 171-192. Also see: http://vision.psych.umn.edu/www/kersten-lab/demos/shadows.html.
• 6: Paul Rademacher, View-dependent geometry, Proceedings of the 26th annual conference on Computer graphics and interactive techniques, p.439-446, July 1999 [doi>10.1145/311535.311612]
• 7: ROBERTSON, B. Disney lets CAPS out of the bag. Computer Graphics World (July 1994), 58-64.
• 8: ROBERTSON, B. Mixed media. Computer Graphics World (Dec. 1998), 32-35.
• 9: ROBERTSON, B. Deep background. Computer Graphics World (July 1999), 50-51.
• 10: Chris Schoeneman , Julie Dorsey , Brian Smits , James Arvo , Donald Greenburg, Painting with light, Proceedings of the 20th annual conference on Computer graphics and interactive techniques, p.143-146, September 1993 [doi>10.1145/166117.166135]
• 11: Michael A. Shantzis, A model for efficient and flexible image computing, Proceedings of the 21st annual conference on Computer graphics and interactive techniques, p.147-154, July 1994 [doi>10.1145/192161.192191]
• 12: THOMAS, F., AND JOHNSTON, O. Disney Animation: The Illusion of Life. Walt Disney Productions, New York, 1981.
• 13: UNIVERSAL STUDIOS / DREAMWORKS. The Prince of Egypt. Movie, 1999.
• 14: VAN OVERVELD, K., AND WYVlLL, B. Polygon inflation for animated models: A method for the extrusion of arbitrary polygon meshes. Journal of Vision and Computer Animation 18 (1997), 3-16.
• 15: Bruce A. Wallace, Merging and transformation of raster images for cartoon animation, Proceedings of the 8th annual conference on Computer graphics and interactive techniques, p.253-262, August 03-07, 1981, Dallas, Texas, United States
• 16: WALT DISNEY PRODUCTIONS. Tarzan. Movie, 1999.
• 17: Leonard C. Wanger , James A. Ferwerda , Donald P. Greenberg, Perceiving Spatial Relationships in Computer-Generated Images, IEEE Computer Graphics and Applications, v.12 n.3, p.44-51, 54-58, May 1992 [doi>10.1109/38.135913]
• 18: WARNER BROTHERS. The Iron Giant. Movie, 1999.
• 19: Lance Williams , Galen Gornowicz, 3D rendering effects for 2D animation, ACM SIGGRAPH 99 Conference abstracts and applications, p.227, August 08-13, 1999, Los Angeles, California, United States [doi>10.1145/311625.312112]
• 20: WILLIAMS, L. Shading in two dimensions. Proceedings of Graphics Interface 91, 143-151.
• 21: Lance R. Williams, Topological Reconstruction of a Smooth Manifold-Solid From Its Occluding Contour, University of Massachusetts, Amherst, MA, 1994
• 22: Daniel N. Wood , Adam Finkelstein , John F. Hughes , Craig E. Thayer , David H. Salesin, Multiperspective panoramas for cel animation, Proceedings of the 24th annual conference on Computer graphics and interactive techniques, p.243-250, August 1997 [doi>10.1145/258734.258859]
• 23: Robert C. Zeleznik , Kenneth P. Herndon , John F. Hughes, SKETCH: an interface for sketching 3D scenes, Proceedings of the 23rd annual conference on Computer graphics and interactive techniques, p.163-170, August 1996 [doi>10.1145/237170.237238]
• 24: Song Chun Zhu , Alan L. Yuille, FORMS: a flexible object recognition and modeling system, International Journal of Computer Vision, v.20 n.3, p.187-212, Dec. 1996

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism
          Subjects: Animation

Additional Classification:
  H. Information Systems
  H.5 INFORMATION INTERFACES AND PRESENTATION (I.7)
      H.5.1 Multimedia Information Systems
          Subjects: Animations

  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.7 Three-Dimensional Graphics and Realism
          Subjects: Color, shading, shadowing, and texture

General Terms:
Design, Experimentation, Performance, Theory

Keywords:
NPR, cel animation, inflation, shadows, sketching