Lecture 16

Foundational ideas

• different kinds of npr trees.
• leaves: Depth-differencing algorithm using the z buffer.
• leaves: disk size and depth difference threshold.
• leaves: abstract primitives (ie leaves)
• trunk: Difference image algorithm and Floyd-Steinburg as the alternate. See M. Salisbury, M. Wong, J. F. Hughes, and D. Salesin. Orientable textures for image-based pen-and-ink illustration. In SIGGRAPH ’97 Conference Proceedings. ACM SIGGRAPH, 1997.
  • Difference image algorithm builds on ideas of user input for tone, direction and texture
  • Each stroke covers some of the importance in a region computed using a blur.
  • comparison of blurred illustration with original image resets importance.
  • Next stroke gets the next-most important area.
  • iterate until all importances are below a certain threshold.
  • Floyd-Steinburg dithering discussion at Wikipedia.
• everything: lod through non linear mapping on depth differencing.
• and graftals.