pigmented colorants: dependence on media and time - Cornell ...

specifying pigments works adequately for creating a wide range of plausible paints,
without the careful measurements needed for true K-M theory.
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Figure 4.9: Various synthetic pigments determined interactively from
Curtis et al. The swatches are painted over a black stripe to distinguish
the more opaque pigments from transparent ones. Adapted
from [CAS + 97].
The optical compositing equations are used to determine the overall reflectance
of the layers and reasonable results are achieved. Although the watercolor renderer
runs too slowly for interactive painting, the work demonstrated that compositing
many glazes of pigments using the K-M model was feasible in real-time. The
model used simpler rendering and a lower resolution during user interaction, and
then added more detail and more accurate colors as a post-processing step.
Rudolf et al. used the same form as Curtis et al. in their wax crayon simu-
lation [RMN03]. Crayons were treated as a translucent <strong>pigmented</strong> material (this
is different from real world crayons, as they contain other impurities). The model
used three wavelengths for the K-M coefficients and the crayon colors were sim-
ilarly not derived from real-world measured materials. The model was also not
fast enough for real-time rendering, but still served as a good preview-and-render
system (strokes took 0.3-2 seconds to render on a high end workstation of the time
of the paper).
However, there are issues with these implementations of Kubelka-Munk theory.