Jeremy M. Praay wrote:

> I'm still playing around with Lightsys, and the more I learn, the more 
> questions I have.  :-)

   You're not the only one! :) Seriously, I only had the initial idea and
zero knowledge about all the matters involved. Ive and others helped a
lot, and the set of macros can do a lot of things, but I really don't
understand all of them.

> My question(s) at this point:
> What are the benefits of using the reflective spectral data (e.g. 
> RS_White_Paint_1) over normal pigments?  Is it simply that the RS values 
> will look better under a much wider range of lighting?  Is it ok to mix 
> normal rgb pigments (e.g. rgb <1,0.8, 0.6>) along with the RS values?

   Technically, the advantage is that you have sampled colors, wich
should look realistic per se. Also, you have "abstract" spectrums that
you can "visualize" under any color space and with any white point, so
you can comunicate colors accuratelly, but this is not of much use with
POV-Ray.

   Practically, the important point is that you don't have to bother
making colors for pigments of known materials. I find it specially
useful with colors wich are difficult to get right, like the green
pigments of plants. It accomplishes the same goal as sampling the colors
from a photo, but with the advantage that the colors are not "changed"
by the lighting on the photo, the camera white balance, etc...

   Mixing with non-sampled colors is not a problem, but you should
adjust them to look similar to the sampled ones in brightness and
saturation, so it's better to use one of both types only.

> Lightsys is an amazing set of includes/macros which everyone should probably 
> be using, but at this point, I don't understand it very well.  Some day, it 
> would be nice to have a good tutorial "Lightsys for Dummies" or something. 
> Perhaps I'll begin writing it up, if I ever get to the point that I truly 
> understand enough of it.

   Yeah... I've that tutorial on the to-do list, who know for how many
years... as I mentioned, the main problem is that I don not fully
understand all the functionality (appart from lazzines, that is).

> As always, any insight would be appreciated.

   Hope that helped as a start...

--
Jaime

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