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

color representation, it is not feasible to store full-spectrum K and S samples on
a per-pixel basis or compute it interactively. Most naturally occurring spectra are
fairly smooth functions and hence are approximated by polynomials of moderate
degree. After selecting a light spectra, the model chooses eight sample wavelengths
and weights. A better implementation would focus more weight on the response
matching functions, as some of the outlying sample wavelengths do not maximize
their effectiveness in Baxter’s model. A Gaussian quadrature integration scheme
is used to compute the final conversion of per-wavelength K-M diffuse reflectances
to RGB for display.
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Figure 4.10: The left column shows graded mixtures of Yellow Ochre
and Prussian Blue under a 5600K light. The right four columns show
computer simulations of the mixtures using different techniques. As one
can see, linear RGB incorrectly predicts brown. While IMPaSTo does
not match the scanned colors exactly, it is important to note that the
8-sample Gaussian quadrature is almost identical to using 101 samples.
Thus, given more accurate data as input, the samples could be matched
very closely. Adapted from [BWL04].
Unlike previous K-M implementations, this work offers true real-time rendering.
The model is realized using programmable fragment shaders on graphics hardware.