[Radiance-general] Composing multiple radiance images

[Jack de Valpine]

Hi Giovanni,

As Lars has pointed out, rad typically ends an image with a call to 
pfilt, which WILL adjust the exposure either implicitly per image 
(likely the source of your variations) or explicitly by
specifying what pfilt should do in your rif file.

-Jack


-- 
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction


On 4/18/2012 6:19 AM, Lars O. Grobe wrote:
> Hi Giovanni!
>> I am not performing any filtering but maybe there is something happening
>> behind the scenes...
>> I simply set up a job generating 9 images using rad and then a simple
>> pcompos line to tile them together
>>
>>     pcompos -a 3 test00*.pic>  composite.pic
>>
>> is this offering more insights?
> rad will typically call pfilt
>
> 1) to filter down resolution (at any quality setting not equal to LOW) 
> to achieve antialiasing as well as
> 2) to apply a useful exposure (at any quality setting).
>
> If you want to assemble the filtered images, you should set a common 
> exposure value to all of them. See the manpage of rad, where the 
> EXPOSURE variable is explained as well as how to find a suitable value.
>
> You can also simply keep the unfiltered images as generated by rpict. 
> You could then assemble the raw images and filter the complete, 
> assembled mosaic. Tell rad to keep the unfiltered images by specifying 
> a name pattern using the RAWFILE variable. Again, the details are 
> explained in the manpage of rad.
>
> If you want to read numerical values from filtered images, usually the 
> -o option are of help. This gives you access to the original pixel 
> values by reversing the exposure mapping performed by e.g. pfilt. See 
> e.g. the manpage of pvalue.
>
> Cheers, Lars.
>
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