Non-Photorealistic Computer Graphics Library

Representation and acquisition models for expressive rendering

Author(s): Pascal Barla.
PhD Thesis: Institut National Polytechnique de Grenoble, 2006.
[BibTeX]

Abstract:
Expressive rendering is a field that emerged around the beginning of the 90s as an alternative to the common trend in computer graphics to produce ever more realistic renderings. By producing "non-photorealistic" imagery, researchers tried to mimic the way artists create paintings and drawings, in order to capture many of these qualities that differentiate them from photographs. The field grew consequently and nowadays it is an inherent part of computer graphics, with expressive rendering papers published in the most important computer graphics conferences and journals, and even a dedicated biennial symposium since 2000, the International Symposium on Non-Photorealistic Animation and Rendering (NPAR). Besides this sudden growth of interest, expressive rendering is still a young research field and naturally, most of the previous work proposed specific solutions to specific problems, nearly always imitating traditional techniques. This thesis proposes to investigate expressive rendering from a more principled point of view, through two main issues which will be presented below: representation, or how to balance user interaction and computer automation to give an intended style to a representation; and acquisition, or how to analyse stylistic information input by a user in order to apply it elsewhere in a representation. Before going into greater detail about expressive rendering, we should first direct our attention to the notion of "realism", from which it tries to depart. To this end, we briefly consider, in the next section, how the quest of realism evolved in art history, before relating expressive rendering to this evolution. We also give here a first glimpse at the connections that tie human vision to any expressive representation, which will be an underlying theme. Finally, we give an overview of the different parts that constitute this thesis. A deeper description of traditional techniques and related work in expressive rendering can be found in each part.