Game Development Reference
In-Depth Information
Schlick (1994) presented practical methods of tone mapping with an objective of
efficient calculations, with few intuitive parameters. For this purpose, he used
rational fractions of degree 1 to apply real luminance on displayable values;
In 1999, Tumblin and Turk (1999) suggested the LCIS method (Low Curvature
Image Simplifier). This method separates the input image (real or computer-
generated) into large zones and fine details, compressing the first and maintaining
the latter. Note that the basic idea is taken from artists' techniques.
Tone mapping for dynamic images
As mentioned in the introduction, the human visual system is capable of perceiving the
luminance in the range of 10 6 to 10 6 cd
m 2 . This is possible thanks to a complex
process of visual adaptation, which is not momentary. It is thus important to be able to
simulate this temporal aspect of visual adaptation. We will now present certain models
which perform interactive tone mapping.
·
Fewerda et al. (1996) developed a model that takes into account the change in
the appearance of colour, visual acuity and temporal sensitivity, while maintaining
global visibility. This model is based on Ward's model (Ward, 1994) for cones and
on the threshold data for rods and uses a psychophysical model of adaptation;
Pattanaik et al. (2000) suggested an operator of tone mapping that depends
on time. It is based on the model by Tumblin and Rushmeier (1993), with an
adaptation model and an appearance model;
Durand and Dorsey (2000) described a model that uses data on visual adaptation
and which is based on the model of Fewerda et al. (1996).
We will also mention the article (Drago et al., 2003) in which the authors compare the
results obtained with seven tone mapping operators.
Section 15.1 was written by Pascal Guitton, section 15.2 by Mathias Paulin and
section 15.3 by Bernard Péroche.
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