Oops! The resolution I gave to pvalue doesn't match the resolution in
vwrays and rtrace. I was testing a higher resolution so I could see detail
in the image, but forgot to change it back to 100 after pasting into the
email. Here's the correct command:
vwrays -ff -vf test.vp -x 100 -y 100 | \
rtrace `vwrays -d -vf test.vp -x 100 -y 100` -ffa -om test.oct | \
awk '{if($1=="window") print 1.0; else print 0.0;}' | \
pvalue +x 100 -y 100 -h -da -b -r | \
ra_tiff - alpha.tif
Also, you might be able to use rcalc in place of awk. It depends on
whether rcalc can compare strings in an if statement. I don't know enough
about rcalc to know if it's possible.
Andy
On Feb 24, 2012, at 2:25 PM, Andy McNeil wrote:
I kinda like Iebele's method approach better than using black and white
materials. Using rtrace -om you can create alpha channels using the same
octree that you use for a rendering. And you can also create many alpha
images for different materials with the same model. It just seems less
work than fussing with material files.
Iebele, the main thing you're missing is pvalue to convert the data stream
to image format. I also used awk for the if statement. Here's a complete
command:
vwrays -ff -vf test.vp -x 100 -y 100 | \
rtrace `vwrays -d -vf test.vp -x 100 -y 100` -ffa -om test.oct | \
* awk '{if($1=="window") print 1.0; else print 0.0;}' *| \
* pvalue +x 500 -y 500 -h -da -b -r *| \
ra_tiff - alpha.tif
Andy
On Feb 24, 2012, at 1:29 PM, giulio antonutto wrote:
yes, this was 
(sorry missed your reply)
G
On 24 Feb 2012, at 19:45, Jack de Valpine wrote:
Hi Iebele,
I have done a few different things to achieve this over the years. The one
that come most readily to mind is to prep an alternate material file with a
black (0 0 0) and white (1 1 1) material assigned as needed. This is one
reason the "alias" material option can be quite handy when assigning
materials to geometry! With the correct black/white materials this can be
rendered out very quickly with -ab 0 and -av 1 1 1.
I have also done something where (with scripting) you can specify a
material name that then get white and everything else gets black. It has
been a while so I do not quite remember off hand, but I think that this can
also be setup as a big pipe in radiance and using radiance's functional
language.
The first way is pretty easy and if you need to do lots of it then it is
possible to script the switching of material assignments. One challenge
though is that if you use instances (frozen octrees) you need to remember
to assign a material accordingly. Another challenge is thinking about
transparencies that might need to be captured in the process...
Regards,
-Jack
--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction
On 2/24/2012 2:24 PM, Iebele Abel wrote:
Hi group,
Whilst finding a method to create alpha channels for my rendered image,
I'm playing with vwrays and rtrace. What I intend is to create an image in
which
geometry modified by a particular modifier is rendered white, whilst the
geometry modified otherwise is rendered black. The command below comes
close to this, it has as output the modifiers for each surface hit:
vwrays -ff -vf test.vp -x 100 -y 100 | rtrace `vwrays -d -vf test.vp -x
100 -y 100` -ffa -om test.oct | more
Output of this command is like:
...
floor
floor
floor
window
window
etc...
Now I want that, for example, each occurrence of "window" sends 3
"bright" RGBE primaries to stdout, and every other string sends 3 "dark"
RGBE primaries to stdout. I can do this by writing a small program (instead
of piping to 'more' as in the example above), but I wondered if there is a
method using native Radiance tools to do it.
In pseudo code (bold) I think about something like this (where 1
represents a value considered as white in the output, and 0 represents
black) :
vwrays -ff -vf test.vp -x 100 -y 100 | rtrace `vwrays -d -vf test.vp -x
100 -y 100` -ffa -om test.oct | *if (stdin == "window") fprintf(stdout,
"1 1 1" ); else fprintf ( stdout, "0,0,0"); *| ra_tiff - alpha.tif
So my questions are:
1. how do I format the output of stdout as Radiance RGBE?
2. can I do this using native Radiance tools?
Thanks for any hints.
-Iebele
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