[Radiance-general] 3.8 Falsecolor Scale

[Gregory J. Ward]

Hi Rob,

Thanks for your feedback.  In retrospect, it would have been smart to  
add an option to get back the old color scale, and I can work on  
adding one.  In the meantime, you can alias your falsecolor to:

	falsecolor -r '1.6*v-.6' -g 'if(v-.375,1.6-1.6*v,8/3*v)' -b '1-8/3*v'

to get back the old scale.  Easier might be to uncomment lines 14-16  
in your falsecolor script and comment (or remove) lines 17-19.

If anyone has references to a preferred scale that runs through at  
least 8 named colors on a natural-appearing scale, I'd love to hear  
about it.

Cheers,
-Greg

> From: Rob Guglielmetti <rpg at rumblestrip.org>
> Date: November 10, 2006 1:34:35 PM MST
>
> Hi Greg,
>
> Well, I have been using the new falsecolor scale (in conjunction  
> with that very cool vwrays trick you developed with John M. to  
> render non-planar clipping "planes" a while back -- very nice!!!),  
> and I have to agree with Axel that it's very unusual.  While I  
> totally applaud the effort to provide more color points from which  
> to pick off values, there are a couple of issues I'd like to point  
> out:
>
> First off, everyone I've ever "trained" in the use of these images  
> and indeed most lighting professionals who are facile with the  
> interpretation of these images expect blue to represent the lowest  
> and red to represent the most intense values.  I'm not up on color  
> spaces and indeed even have partially "defective color vision", as  
> the FAA kindly calls it, but my brain seems to understand a low-to- 
> high intensity progression of blue-cyan-green-orange-red.  It makes  
> sense to me, but more importantly it's what I've been generating  
> (and teaching) for years.  So to force my brain to remember that  
> blue now trumps magenta in intensity has been a bit of a trick this  
> morning.  I wonder what the impact will be with clients already  
> versed in the interpretation of the older scale of these images.
>
> Second, I have generally overcome the limited color range by  
> playing with scale limit and logarithmic mappings whenever a more  
> finite scale is required.  This often limits the usefulness of the  
> scale range to a specific area of interest in the image, perhaps a  
> wall with a subtle luminance gradient that I wish to study, but it  
> works.  I agree it's more work, but again it successfully applies  
> the currently-accustomed color scale to a fine-grained area of  
> interest.
>
> I propose two solutions to this.  One, re-ordering the colors to  
> better fit the old scale, at the very least putting blue at the  
> bottom and red back at the top, spectral/thermal realities  
> notwithstanding.  Two, give the user an option of using the old  
> scale or the new one.  Like I said, I think the additional colors  
> help, and maybe your new scale really is superior, once a little  
> adaptation occurs; the option to use either scale might ease that  
> transitional process.  Thoughts?
>
> - Rob G.