[Radiance-general] expert assistance/guidance please?

[Greg Ward]

> From: John An <whollycow@mac.com>
> Date: Wed May 14, 2003  11:04:41  AM US/Pacific

Rob G. did a nice job answering most of your questions, so I'll just 
touch on the ones he missed...

> Greg Ward replied:
> You're correct -- the pattern affects the total material
> reflectance/transmittance.  To avoid this, run pfilt on your picture in
> advance, like so:
>
> pfilt -e 2 orig.pic > normalized.pic
>
> The "normpat" script will do this for you, and blend the edges for
> better tiling as well if that's what you have in mind.
>
> To which I ask:
> I'm not sure I understand how adjusting the exposure of an already 
> processed
> image will correct the reflectance of a material.  Could you help me
> understand this a bit more?

The Radiance colorpict primitive uses the final pixel values after 
exposure adjustment to modify the material color.  Therefore, adjusting 
the picture so that the average is 1 (as pfilt -e 2 will do) avoids 
biasing your average value.

> Final point regarding the publishing of Rendering with Radiance:
> I'm sure it is a conscious decision not to digitize the entire book 
> into a
> print disabled .pdf, but could some electronic version be an option?

That's a good suggestion.  I have the PDF for the book, which Rob 
Guglielmetti assembled from the pieces, and it should be easy enough to 
disable printing on it.  Personally, I think the book is much less 
useful in electronic-only form, but if that's all you can get, it's 
certainly better than nothing.  I'll confer with my coauthors about 
distributing the PDF.  We are looking into print-on-demand publishers, 
and hope to have it available again to book resellers (Amazon, etc.) 
before the Fall.  Until then, we might distribute it to people in 
unprintable form, though that seems really annoying in some respects.

-Greg