Local layering

ABSTRACT

In a conventional 2d painting or compositing program, graphical objects are stacked in a user-specified global order, as if each were printed on an image-sized sheet of transparent film. In this paper we show how to relax this restriction so that users can make stacking decisions on a per-overlap basis, as if the layers were pictures cut from a magazine. This allows for complex and visually exciting overlapping patterns, without painstaking layer-splitting, depth-value painting, region coloring, or mask-drawing. Instead, users are presented with a layers dialog which acts locally. Behind the scenes, we divide the image into overlap regions and track the ordering of layers in each region. We formalize this structure as a graph of stacking lists, define the set of orderings where layers do not interpenetrate as consistent, and prove that our local stacking operators are both correct and sufficient to reach any consistent stacking. We also provide a method for updating the local stacking when objects change shape or position due to user editing - this scheme prevents layer updates from producing undesired intersections. Our method extends trivially to both animation compositing and local visibility adjustment in depth-peeled 3d scenes; the latter of which allows for the creation of impossible figures which can be viewed and manipulated in real-time.

REFERENCES

• 1: Adelson, E. H., and Wang, J. Y. A. 1994. Representing moving images with layers. IEEE Transactions on Image Processing 3, 625--638.
• 2: Apple, 1999--2009. Final Cut Pro. http://www.apple.com/finalcutstudio/finalcutpro/.
• 3: Paul Asente , Mike Schuster , Teri Pettit, Dynamic planar map illustration, ACM Transactions on Graphics (TOG), v.26 n.3, July 2007
• 4: P. Baudelaire , M. Gangnet, Planar maps: an interaction paradigm for graphic design, ACM SIGCHI Bulletin, v.20 n.SI, p.313-318
• 5: Frederic Cordier , Hyewon Seo, Free-Form Sketching of Self-Occluding Objects, IEEE Computer Graphics and Applications, v.27 n.1, p.50-59, January 2007 [doi>10.1109/MCG.2007.8]
• 6: Paul E. Debevec , Camillo J. Taylor , Jitendra Malik, Modeling and rendering architecture from photographs: a hybrid geometry- and image-based approach, Proceedings of the 23rd annual conference on Computer graphics and interactive techniques, p.11-20, August 1996 [doi>10.1145/237170.237191]
• 7: Tom Duff, Compositing 3-D rendered images, Proceedings of the 12th annual conference on Computer graphics and interactive techniques, p.41-44, July 1985
• 8: Everitt, C. 2001. Introduction to interactive order-independent transparency. Tech. rep., NVIDIA.
• 9: Takeo Igarashi , Tomer Moscovich , John F. Hughes, As-rigid-as-possible shape manipulation, ACM Transactions on Graphics (TOG), v.24 n.3, July 2005
• 10: Olga A. Karpenko , John F. Hughes, SmoothSketch: 3D free-form shapes from complex sketches, ACM Transactions on Graphics (TOG), v.25 n.3, July 2006
• 11: Kimball, S., and Mattis, P., 1995--2009. The GNU Image Manipulation Program. http://www.gimp.org.
• 12: Mediachance, 2001--2009. Real-Draw PRO push-back tool. http://www.mediachance.com/realdraw/help/pushback.htm.
• 13: Nitzberg, M., and Mumford, D. 1990. The 2.1-d sketch. Computer Vision, 1990. Proceedings, Third International Conference on (Dec), 138--144.
• 14: Thomas Porter , Tom Duff, Compositing digital images, Proceedings of the 11th annual conference on Computer graphics and interactive techniques, p.253-259, January 1984
• 15: Smith, A. R. 1995. Alpha and the history of digital compositing. In Microsoft Technical Memo #7.
• 16: John Snyder , Jed Lengyel, Visibility sorting and compositing without splitting for image layer decompositions, Proceedings of the 25th annual conference on Computer graphics and interactive techniques, p.219-230, July 1998 [doi>10.1145/280814.280878]
• 17: SVG Working Group, 2003. Scalable Vector Graphics (SVG) 1.1 Specification. http://www.w3.org/TR/SVG11/.
• 18: Keith Wiley , Lance R. Williams, Druid: representation of interwoven surfaces in 21/2d drawing, University of New Mexico, Albuquerque, NM, 2006
• 19: Lance R. Williams, Topological Reconstruction of a Smooth Manifold-Solid from Its OccludingContour, International Journal of Computer Vision, v.23 n.1, p.93-108, May 1997 [doi>10.1023/A:1007967925618]

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.3 COMPUTER GRAPHICS
      I.3.3 Picture/Image Generation

Keywords:
animation, compositing, image editing, layers, stacking, visibility