Computer aided inbetweening

ABSTRACT

The production of inbetweens is a tedious task for animators and a complicated one for algorithms. In this paper, an algorithm for computer aided inbetweening and its integration in a pen-based graphical user interface are presented.The algorithm is layer-based, assuming an invariant layering order. It is applicable to animations in a style similar to paper cut out, in which the drawings on the cut-out pieces are inbetweened as well. The content of each key drawing is analysed and classified into strokes, chains of strokes and relations that hold among them. Rules decide what parts of different drawings may be matched. These rules specify allowed changes between relations in key drawings. A cost function based approach determines the correct matching of strokes. Generated animation paths between corresponding strokes determine the resulting inbetweens.To hold for possible mismatchings and to allow for artistic control over the results, the inbetweening algorithm is embedded in a free form graphic user interface. Thus artists are enabled to focus on the part of the inbetweening task computers are not able to solve.

REFERENCES

• 1: N. Burtnyk , M. Wein, Interactive skeleton techniques for enhancing motion dynamics in key frame animation, Communications of the ACM, v.19 n.10, p.564-569, Oct. 1976 [doi>10.1145/360349.360357]
• 2: Edwin Catmull, The problems of computer-assisted animation, Proceedings of the 5th annual conference on Computer graphics and interactive techniques, p.348-353, August 23-25, 1978
• 3: Daniel Cohen-Or , Amira Solomovic , David Levin, Three-dimensional distance field metamorphosis, ACM Transactions on Graphics (TOG), v.17 n.2, p.116-141, April 1998 [doi>10.1145/274363.274366]
• 4: Cassidy J. Curtis, Loose and sketchy animation, ACM SIGGRAPH 98 Electronic art and animation catalog, p.145, July 19-24, 1998, Orlando, Florida, United States [doi>10.1145/281388.281913]
• 5: DURAND, C. X. 1991. The "toon" project : Requirements for a computerized 2d animation system. Computers & graphics 15, 2, 285-293.
• 6: 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]
• 7: Jonas Gomes , Lucia Darsa , Bruno Costa , Luiz Velho, Warping and morphing of graphical objects, Morgan Kaufmann Publishers Inc., San Francisco, CA, 1998
• 8: IGARASHI, T. 1999. Freeform User Interfaces for Graphical Computing. PhD thesis, University of Tokyo.
• 9: IGARASHI, T. 2000. Supportive interfaces for creative visual thinking. In Collective Creativity Workshop. May 7-8, Nara (Japan).
• 10: John Lasseter, Principles of traditional animation applied to 3D computer animation, ACM SIGGRAPH Computer Graphics, v.21 n.4, p.35-44, July 1987
• 11: MADEIRA, J., STORK, A., AND GROSS, M. H. 1996. An approach to computer-supported cartooning. The Visual Computer 12, 1-17.
• 12: MADEIRA, J. 1999. A new region matching-based approach to computer-assisted cartooning. PhD thesis, TU Darmstadt, Aachen.
• 13: NEBEL, J.-C. 1999. Keyframe animation of articulated figures using autocollision-free interpolation. In 17th Eurographics UK Conference'99. April 13-15, Cambridge, UK.
• 14: William H. Press , Brian P. Flannery , Saul A. Teukolsky , William T. Vetterling, Numerical recipes in C: the art of scientific computing, Cambridge University Press, New York, NY, 1988
• 15: 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]
• 16: SCHNEIDER, P. J. 1988. Phoenix : An interactive curve design system based on the automatic fitting of hand-sketched curves. Master's thesis, University of Washington.
• 17: SEAH, H. S., AND FENG, T. 2000. Computer-assisted coloring by matching line drawings. The Visual Computer 16, 269-304.
• 18: Thomas W. Sederberg , Eugene Greenwood, A physically based approach to 2–D shape blending, ACM SIGGRAPH Computer Graphics, v.26 n.2, p.25-34, July 1992
• 19: Thomas W. Sederberg , Peisheng Gao , Guojin Wang , Hong Mu, 2-D shape blending: an intrinsic solution to the vertex path problem, Proceedings of the 20th annual conference on Computer graphics and interactive techniques, p.15-18, September 1993 [doi>10.1145/166117.166118]
• 20: THOMAS, F., AND JOHNSTON, O. 1981. Disney animation : the illusion of life. Abbeville Press, New York.
• 21: WHITAKER, H., AND HALAS, J. 1981. Timing for animation. Focal Press, Oxford.
• 22: WILLIAMS, L. 1991. Shading in two dimensions. In Graphics Interface '91, Morgan-Kaufman Publishers, Canadian Human-Computer Communications Society, 143-151.
• 23: XIE, M. 1995. Feature matching and affine transformation for 2d cel animation. The Visual Computer 12, 419-428.

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.6 Methodology and Techniques
          Subjects: Interaction techniques

Additional Classification:
  I. Computing Methodologies
  I.2 ARTIFICIAL INTELLIGENCE
        I.2.10 Vision and Scene Understanding
            Subjects: Shape
  I.4 IMAGE PROCESSING AND COMPUTER VISION
      I.4.8 Scene Analysis
          Subjects: Object recognition

Keywords:
inbetweening, keyframe animation