[Radiance-general] splitting a render by light sources - rtcontrib

[Santiago Torres]

Hi Will,

Here are some ideas (although you probably know most already)

- make sure you have a recent head version
- make sure that the definitions of the materials are ok (if you want  
to separate 100 lights you need to define 100 light materials and use  
one material in each light)
- the actual names of the materials replace the "light1" "light2" in  
the example
- sometimes the image is too dark and you need to use "a" (for auto  
exposure) in ximage
- make sure the resolution is the same in both commands (I got this  
mistake)
- after "-fcc" is a backtick ` and the same after "best.vf" (in Unix  
this means "execute the command inside and return the result" or  
something like that)
- if you have too many lights, could be you don`t have enough  
descriptors, try the command "csh" (to enter cshell) and then "limit  
descriptors" (the result should be higher than the number of  
materials you want to define, but it`s probably more than 100)

just some ideas. it is probably none of the above. and it would  
surely help more information: what command you actually used, what  
result you get (any error message?) which OS, Radiance version, etc
HTH

Santiago



On Jan 24, 2006, at 11:48 PM, william reynolds wrote:

> hi
>
> i've trying out rtcontrib on this, but whatever settings i use i  
> seem to get just a black screen out. if i run rpict witht the same  
> settings (ie the same view and opt files) i get a good picture  
> (although obviously using all the lights).
> does anyone have any suggestions what i might be doing wrong?
> thanks
> will
>
> ps i am just following the example usage of rtcontrib,  given below.
>
> Francesco Anselmo wrote:
>> Hi Will,
>>> i am trying to use radiance to render a relatively simple model
>>> geometrically - just a simple room, with a box sitting on the  
>>> floor -
>>> but with up to 100 or so light sources. but the difference is that i
>>> want to get a separte image file for each light source - i.e.   
>>> hundred
>>> or so images, with only 1 light on in each. i will then use
>>> superposition and recombine the images later, allowing me to vary  
>>> the
>>> intensities of each light source.
>>>
>>> is there any kind of built in functionality in radiance to allow  
>>> me to
>>> do this, or do i have to write a shell script or something (and  
>>> if so,
>>> can anyone point me towards a good place to learn how! i come from a
>>> very winndows based background)
>> Shell scripts would work, but Greg has recently added to Radiance  
>> rtcontrib:
>> http://radsite.lbl.gov/radiance/man_html/rtcontrib.1.html
>> This man page contains already a good starting example:
>> "
>> To generate a pair of images corresponding to two lights'  
>> contributions:
>>          vwrays -ff -x 1024 -y 1024 -vf best.vf | rtcontrib -ffc  
>> `vwrays -d -x
>>          1024 -y 1024 -vf best.vf` @render.opt -o c_%s.pic -m  
>> light1 -m light2
>>          scene.oct
>> These images may then be recombined using the desired outputs of  
>> light1
>> and light2:
>>          pcomb -c 100 90 75 c_light1.pic -c  50  55  57   
>> c_light2.pic  >  com-
>>          bined.pic
>> "
>> --
>> Francesco
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>
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