[Radiance-general] Generating alpha channels using vwrays and rtrace

[giulio antonutto]

must disagree (oi oi oi!)

glow is normal sensitive so not an option most of the time.

better to use black and white and av 1  1 1 (no sky to cut reflections)

G

On 24 Feb 2012, at 19:54, Greg Ward wrote:

> Hi Iebele,
> 
> Wouldn't it be simpler to introduce an alias for the material you want and set it to "glow" with the desired high brightness?  Take out any other light sources, turn off ambient bounces and ambient value, and render the image.  It would be a lot faster that way.
> 
> Barring that, you can do what you want like so:
> 
> vwrays -ff -vf test.vp -pa 0 -x $XRES -y $YRES | rtrace -h -x $XRES -y $YRES  -ffa -om test.oct  \
> 	| sed -e 's/^window$/1/' -e 's/^[^1].*$/0/' | pvalue -h -r -b -d -y $YRES +x $XRES > mask.hdr
> 
> You need to set your x and y resolution explicitly because pvalue needs them in a form other than the one vwrays -d produces.  This also assumes you have sed and none of your material names starts with the numeral '1'.
> 
> Cheers,
> -Greg
> 
> P.S.  Seems Jack beat me to this....
> 
>> From: Iebele Abel <iabel at iebele.nl>
>> Date: February 24, 2012 11:24:43 AM PST
>> 
>> 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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