[Radiance-general] Display of time lapse at constant brightness

[Greg Ward]

Andy's recommendation would also be mine, but you need the "-I" option to pcond to get it to read the histogram from stdin.

Cheers,
-Greg

> From: Andy McNeil <mcneil.andrew at gmail.com>
> Subject: Re: [Radiance-general] Display of time lapse at constant brightness
> Date: October 3, 2015 8:08:16 AM PDT
> 
> You could also use phisto to create a luminance histogram from all your images and tone map your images using pcond with the all image histogram as input.
> 
> phisto frame*.hdr > allframes.hist
> pcond frame0001.hdr < allframes.hist | ra_tiff - frame0001.tif
> 
> When there's a wide range of illumination conditions I find that pcond with the histogram works best to preserve visibility and maintain consistency between frames.
> 
> Andy
> 
> On Sat, Oct 3, 2015 at 5:45 AM, Chris Kallie <kallie at umn.edu> wrote:
> You can use the -e option in pfilt to adjust by a constant. Instead of using +0, you can use a value without the + symbol that is a fraction of the EXPOSURE value in your header file. -Chris
> 
> 
> On 10/3/15 8:21 AM, ascendilex | Wouter Beck wrote:
> Dear Group,
> 
> I'm trying to display a series of Radiance renderings as a time lapse
> animation.
> 
> I convert (pfilt -e +0 -r .6 -x /2 -y /2 filtered) hdr-images via
> ra_tiff and the resulting tifs are combined into an animated gif via
> (ImageMagick's) convert -delay 200 -quality 100 *.tif time-lapse.gif.
> 
> Each image represents a view of an atrium 1 hour apart.
> The indirectly lit walls of the room that contains my view point get
> displayed darker as the atrium scene brightens up.
> In absolute terms one wall has a luminance of 15 cd/m2 at 9:00. That
> same wall is 29 cd/m2 at 12:00, yet when displayed (using ximage) it
> appears darker.
> Exposure times in the headers are of course quite different:
> vp-A-092108.00.pic:EXPOSURE=3.008155e+00
> vp-A-092112.00.pic:EXPOSURE=3.957302e-01
> 
> 
> Basically I want the tone mapping according to a constant (perhaps log)
> scale for all images.
> 
> How can that be accomplished?
> (Looks like falsecolor could do this if it also had a greyscale palette.)
> 
> Best regards,
> 
> Wouter
> 
> 
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