[jfrancis]

3D renderers as old as Renderman (The Renderman Companion, Steve Upstill, p. 42) and as young as Maxwell, have had the ability to represent colors in higher than the usual 3 samples (at red, green, and blue) along the spectrum. A common practice (among those who use multi-spectral sampling) is to represent colors with 9, and sometimes 12, wavelength samples.

This is especially useful for representing colors in so-called "subtractive color" situations, such as the layering of transparent colored objects, or their interreflections against each other, or the color falloff of objects underwater, or in exotic atmospheres.

Has the idea of multi-spectral sampling made it into Painter's internal color-mixing calculations? In the artist's oils routines, for example?

I'm wondering how much real world Physics and real world paint testing and mixing has made its way into the Painter IX color engine.

I guess I'm sort of asking Jin and John Derry, but if anyone else knows, I'm curious.

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[Jin]

Hi jfrancis,

You can count me out as someone who could answer your interesting question, sorry to say.

John Derry and/or Corel Painter Program Manager Rick Champagne would be your best sources.


Jinny Brown
TutorAlley Forums
Tutorials and Painter Info at PixelAlley

[jfrancis]

For anyone interested, I found a decent explanation of spectral rendering in a comment on a thread at, of all places, FARK.

http://forums.fark.com/cgi/fark/comments.pl?IDLink=1507984

do a search for this comment:

2005-05-31 01:43:29 PM COMALite J

Here's an excerpt:

But still, R, G, B. Problem is, real-world colors don�t work that way. Instead, they reflect differing amounts of different percentages of incoming light, along the visible (and invisible, but we�re dealing with the visible here) portion of the electromagnetic spectrum. And the light sources themselves often cannot be expressed as simple RGB colors.

For instance, the light from sodium vapor lamps appears to be a goldenrod color, about equal to R:1.0, G:0.875, B:0.125. Yet, in real life, that�s not the sort of light it�s actually emitting. It actually emits true yellow light, from the actual yellow portion of the spectrum (rainbow), with almost no red or green to it.

This means that if a car is painted red and parked in a parking lot illuminated by sodium vapor lamps, the red paint would appear dark gray at best, if not black. Ditto a green car (and, of course, a blue car).

Replace the sodium vapor lamps with incandescent lights that are dimmed to produce a similar orangish-yellow color but from an incandescent filament source that has a true color temperature and thus emits lots of red, almost as much true yellow, and somewhat less green, the light would appear to be the same color, and yet the red car would appear just as red as it would under white light or daylight of the same overall intensity, and the green car would appear as a slightly dimmer-than-normal green.