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

[giulio antonutto]

Yes, that is it.
Because most of the time people building the 3d do not pay attention to normals… 
so if you are using radiance and rely on model coming from elsewhere, either you have to spend a long time flipping polygons or you use another route.
which sometimes is running two things (one xform'ed -I) and add them up or simply  use the black/white and av trick 
:-)
G


On 24 Feb 2012, at 21:45, Greg Ward wrote:

> You mean glow isn't visible from the back side, right?  The output from the front side is the same in all directions, but the back side emits 0.  I didn't think of this issue, but I suppose it matters for a lot of scenes...  Good point!
> 
> -Greg
> 
>> From: giulio antonutto <antonutto at yahoo.it>
>> Date: February 24, 2012 1:29:20 PM PST
>> 
>> 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....
> 
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