@inproceedings{Tolba:1999:SPS,
  opturl = {},
  author = {Osama Tolba and Julie Dorsey and Leonard {McMillan}},
  booktitle = {Proceedings of the 12th Annual {ACM} Symposium on User Interface
               Software and Technology, UIST'99},
  optstatus = {url},
  address = {New York},
  localfile = {papers/Tolba.1999.SPS.pdf},
  abstract = {Freehand sketching has long had appeal as an artistic medium for
              conceptual design because of its immediacy in capturing and
              communicating design intent and visual experience. We present a
              sketching paradigm that supports the early stages of design by
              preserving the fluidity of traditional freehand drawings. In
              addition, it attempts to fill the gap between 2D drawing programs,
              which have fixed views, and 3D modeling programs that allow
              arbitrary views. We implement our application as a two-dimensional
              drawing program that utilizes a projective representation of
              points — i.e. points that lie on the surface of a unit sphere
              centered at the viewpoint. This representation facilitates the
              production of novel re-projections generated from an initial
              perspective sketch and gives the user the impression of being
              immersed in the drawing or space. We describe a method for
              aligning a sketch drawn outside the system using its vanishing
              points, allowing the integration of computer sketching and
              freehand sketching on paper in an iterative manner. The user
              interface provides a virtual camera, projective grids to guide in
              the construction of proportionate scenes, and the ability to
              underlay sketches with other drawings or photographic panoramas.},
  title = {{S}ketching with {P}rojective {2D} {S}trokes},
  publisher = {ACM Press},
  optmonth = {nov~7--10},
  doi = {http://doi.acm.org/10.1145/320719.322596},
  pages = {149--158},
  year = {1999},
}