[Radiance-general] Tone mapping for animation

Tue Oct 22 09:45:12 PDT 2013

Perfect, thanks for the clarification Greg!

Another short note:
I just found out that one thing that also made my life hard with getting
the scene constantly exposed was the inclusion of a time stamp in the image
with psign before sending the image through pcond... stupid error on my
side as this introduces virtual luminances that are not in the scene.

2013/10/22 Greg Ward <gregoryjward at gmail.com>

> I don't use hdr2jpeg myself, and it isn't distributed with Radiance.
>  Depending on which version you have, it applies either a Reinhard TMO or a
> variant of the histogram adjustment operator in pcond, but there's no way
> to tell it to use a specific curve as you can with the pcond -I option Jack
> mentioned.  The latter technique with phisto is what I generally use if I
> want a sequence exposed the same.  And, you can go on using the same
> histogram for future frames so long as they don't change too much from the
> range of past frames.
>
> Cheers,
> -Greg
>
> *From: *David Geisler-Moroder <david.moroder at gmail.com>
>
> *Date: *October 22, 2013 8:50:27 AM PDT
>
> *
> *
>
> Hi Jack,
>
> I guess Greg is the only one to answer that question.
> However, I guess some tone mapping has to be done as the HDR-JPG format is
> backwards compatible and all viewers that read JPGs also read that. So
> somehow they need to get get the tonemapped information...
>
> Cheers,
> David
>
>
> 2013/10/22 Jack de Valpine <jedev at visarc.com>
>
>>  Hi David,
>>
>> Great, glad it helped!
>>
>> I have not used the hdr2jpeg utility so I am not really sure what it
>> does. My impression is that it converts to a jpeg that contains hdr
>> information. I do not think that it does tone mapping though. Perhaps
>> others can weigh in...
>>
>>
>> Best,
>>
>> -Jack
>>
>> --
>> Jack de Valpine
>> President
>>
>> Visarc Incorporatedwww.visarc.com
>>
>> channeling technology for superior design and construction
>>
>> On 10/22/2013 11:14 AM, David Geisler-Moroder wrote:
>>
>>    Hi Jack, hi Lars,
>>
>>  thanks a lot for the quick response!
>>  Jack, your second hint exactly did what I was looking for. I tried to
>> use pcond first, but didn't think of the possibility to use a histogram...
>>
>>  Sorry, if my description was somehow cryptic, but you exactly found what
>> I wanted...
>>
>>  Just for information: the pfilt exposure corrections do not help in my
>> case because the tone-mapping that is done in the HDR2LDR conversion (with
>> hdr2jpeg / ra_tiff or similar) does the tone mapping for each single frame
>> independent from the other images. (But maybe I just got something terribly
>> wrong here...!?)
>>
>>  Thanks!
>>  David
>>
>>
>>
>> 2013/10/22 Jack de Valpine <jedev at visarc.com>
>>
>>>  Hi David,
>>>
>>> I am a little unclear on what you want to accomplish but here are a few
>>> thoughts.
>>>
>>>    1. time series animation with constant exposure on successive frames
>>>    - use pfilt -1 -e [constant exposure setting] for each frame
>>>     2. time series animation with tone mapping function on successive
>>>    frames - use pcond and phisto, phisto will compute a histogram across a
>>>    series of frames pcond can then use the results from phisto to tone map the
>>>    frames according to selected tone mapping operator, there is a an example
>>>    in the man page for pcond
>>>
>>> I think that maybe where I am confused by your description is that since
>>> Radiance output is already HDR, setting exposure is really a post process.
>>> I think that what you are looking for is the second option that I describe
>>> above.
>>>  Not sure if this answers your questions, but perhaps gives you some
>>> things to look into.
>>>
>>> Best,
>>>
>>> -Jack
>>>
>>> --
>>> Jack de Valpine
>>> President
>>>
>>> Visarc Incorporatedwww.visarc.com
>>>
>>> channeling technology for superior design and construction
>>>
>>>  On 10/22/2013 9:45 AM, David Geisler-Moroder wrote:
>>>
>>>   Hi all,
>>>
>>>  I have a question concerning the tone mapping procedures implemented in
>>> the Radiance tools.
>>> For an animation of a full day I would like to get something similar
>>> that a camera would do that just takes a picture every 5 minutes with the
>>> same settings (exposure time and aperture). Rendering the images for every
>>> 5 minutes is not a problem, however, I stuck when trying to convert the
>>> HDRs to some tonemapped images. As far as I got it, In ra_jpeg/hdr2jpeg no
>>> exposure can be given at all, in ra_tiff/ra_bmp only relative exposures can
>>> be applied.
>>>
>>>  Thus my question: is it possible to explicitly set the exposure used
>>> in the tonemapping process with any tool in Radiance?
>>>
>>>  Thanks in advance!
>>>  David
>>>
>>>
>>>
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>>>
>>
>>
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