@techreport{Bartesaghi:2002:NPR,
  optpostscript = {},
  number = {1895},
  month = nov,
  optnote = {},
  author = {Alberto Bartesaghi and Guillermo Sapiro},
  optkey = {},
  optannote = {},
  url = {http://www.ima.umn.edu/preprints/nov2002/nov2002.html#1895},
  address = {Minneapolis, USA},
  localfile = {papers/Bartesaghi.2002.NPR.pdf},
  optkeywords = {},
  optciteseer = {},
  optdoi = {},
  optwww = {},
  title = {{N}on-{P}hotorealistic {R}endering from {S}tereo},
  abstract = {A new paradigm for automatic non-photorealistic rendering is
              introduced in this paper. Non-photorealistic rendering (NPR)
              provides an alternative way to render complex scenes by
              emphasizing high level or salient perceptual features.
              Particularly, the pen-and-ink rendering style produces
              sketchy-like drawings that can effectively communicate shape and
              geometry. This is achieved by combining drawing primitives that
              mimic ink patterns used by artists. Existing NPR approaches can be
              categorized in two groups depending on the type of input they use:
              image based and object based. Image based NPR techniques use 2D
              images to produce the renderings. Object based techniques work
              directly on given 3D models and make use of the full volumetric
              representation. In this paper we propose to enjoy the best of both
              worlds developing an hybrid model that simultaneously uses
              information from the image and object domains. These two sources
              of information are provided by a calibrated stereoscopic system.
              Given a pair of stereo images and the calibration data we solve
              the stereo problem in order to extract the normal and principal
              direction fields, which are fundamental to guide a texture
              synthesis algorithm that generates the NPR renderings. In
              particular, normals guide tonal variations, while principal
              directions determine the orientation of stroke-like texture
              patterns. We describe a particular, fully automatic,
              implementation of these ideas and present a number of examples.},
  type = {IMA Preprint Series},
  year = {2002},
  institution = {Institute for Mathematics and its Applications, University of
                 Minnesota},
}