Well, thanks a lot folks, for your comments on this. Jacks suggestion has been used over years, but recently we started using tmeshes, and because of that parts of the octree is frozen. So we had to find some other solution, without messing around with multiple material files for each tmesh. I've tried both Gregs and Andys suggestions and they both work really smooth. When running the command in a bash script I found awk performing about 25-30% faster as sed. See below how the commands are put in bash (not checking argument values etc.) and their timed outputs pasted thereafter.
There remain some issues in the script when rendering non-square images (like 1920x1080 HD), but that will be worked out. All together this has all been very helpful,
Cheers,
Iebele
--- ralpha script ---
#!/bin/bash
if ( ! getopts "
m:x:y:o:" opt ); then
echo "Usage: `basename $0` -v viewfile -m modifier -x xres -y yres -o octree" >&2
exit
fi
while getopts "v:m:x:y:o:" opt; do
case $opt in
v) viewfile=$OPTARG
;;
m) modifier=$OPTARG
;;
x) xres=$OPTARG
;;
y) yres=$OPTARG
;;
o) octree=$OPTARG
;;
esac
done
echo "using awk" >&2
time vwrays -ff -vf $viewfile -x $xres -y $yres | \
rtrace `vwrays -d -vf $viewfile -x $xres -y $yres` -ffa -om $octree | \
awk -v v1=$modifier '{if( $1 == v1 ) print 1.0; else print 0.0;}' | \
pvalue +x $xres -y $yres -h -da -b -r
echo "using sed" >&2
time vwrays -ff -vf $viewfile -pa 0 -x $xres -y $yres | \
rtrace -h -x $xres -y $yres -ffa -om $octree | \
sed -e "s/^$modifier/1/" -e "s/^[^1].*$/0/" | \
pvalue -h -r -b -d -x $xres -y $yres
--- output --
./ralpha -v hermitage_brug01.vp -m water -x 16000 -y 16000 -o export.oct > /dev/null
using awk
real 5m21.743s
user 8m51.873s
sys 0m7.116s
using sed
real 7m55.060s
user 13m41.563s
sys 0m5.199s
2012/2/25 Andy McNeil <[email protected] <mailto:[email protected]>>
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 <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
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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m:x:y:o:" opt ); then