@article{CigScoTar05,
   author = {Paolo Cignoni and Roberto Scopigno and Marco Tarini},
   title = {A simple Normal Enhancement technique for Interactive Non-photorealistic Renderings},
   editor = {S. Gumhold and S. Noll},
   journal = {Computers and Graphics},
   volume = {29},
   number = {1},
   year = {2004},
   month = {February},
   pages =  {125--133},
   publisher = {Elsevier Science},
}


@techreport{CigScoTar03,
   author = {Paolo Cignoni and Roberto Scopigno and Marco Tarini},
   title = {A simple Normal Enhancement technique for Interactive Non-photorealistic Renderings},
   abstract = {We present a simple technique to improve the perception of the
               shape of an object. Bump mapping is well-known in the computer
               graphics community for providing the impression of small-scale
               geometrical features, which are not explicitly modelled. Here,
               we propose a similar approach (variation of normals) for the
               purpose of enhancing the perception of a given geometry. Our
               approach is based on a simple modification of the surface normals
               in order to enhance the geometric features of the object during
               the rendering. The enhanced normals produced by this approach
               can be used in any rendering technique. The technique presented
               is particularly well suited to improve the rendering of mechanical
               parts where common straightforward shading techniques can often
               generate shading ambiguities.},
   institution = {Istituto di Scienza e Tecnologia dell’Informazione},
   year = {2003},
   number = {2003-TR-18},
   address = {Pisa, Italy},
   month = {},
   note = {}
}