I tried to implement a colour conversion from RGB (display) to
RGB (Radiance) for my Sketchup exporter with information I could
find in the archive and on the web. I had some sort of conversion
working but the closest match is achieved by using the RGB values
directly in Radiance (without any of the -> XYZ -> xyY -> etc steps).
So I'm wondering: Do you have to convert the colour triples at
all to get a visual match in Radiance? And if so, has anyone
already written a script for this or can point out a simple
documentation on the process?
RwR, ch. 5.1.4 Estimating Surface Color (new edition) states that the
Radiance primaries are 'very similar to the primary colors used in
computer RGB monitors, although there is no widely accepted standard.'
Considering the colour variations you get with different monitors, and
even different settings of the same monitor, it's probably not worth
it.
To be honest, I didn't even look into different RGB colour systems.
I was more concerned with
a) improving on the Photoshop colour picker technique (also described
in RwR), which requires:
a1) converting the 0-255 range to a 0-1 range, and also
a2) applying a gamma correction
b) creating the material data bases. There are currently well above
20000 entries.
c) coding import filters for other colour notations
While a1), b) and c) are done, I haven't actually had the time to look
at gamma correction yet, although it should be fairly
straight-forward. This is why the swatch may appear rather different
to the preview render, which has a gamma of 2.2
Axel