[Radiance-general] Measuring Illuminance

[Randolph Fritz]

Also, if you have an irradiance image and just want to know the illumination at a few points, you can (on Macs and other Unix-like systems) display the image with ximage and use the ‘l’ command to find values.

-- 
Randolph M. Fritz, Lighting Design and Simulation
+1 206 659-8617 || rmfritz3 at gmail.com <mailto:rmfritz3 at panix.com>
> On Feb 14, 2016, at 5:04 PM, Rob Guglielmetti <rob.guglielmetti at gmail.com> wrote:
> 
> There are two basic methods for calculating illuminance with Radiance. You can pass one or more points to rtrace, which will return a value(s) for that specific point(s); the other way is to pass in a view to rpict, which will return values for each pixel in the view. By default, both tools return radiance. If you want illuminance, you need to request irradiance instead of radiance, and then convert that output to illuminance using the standard luminous efficacy function. 
> 
> Specifically, it sounds like you want to know how to get illuminance from the specific image you attached to your question here. In this case, you'd need to re-render the image as an irradiance image instead of a radiance image, using the -i option to rpict. With that image, you could pass it through falsecolor, producing a falsecolor illuminance map or flood plot of the illuminance on all the (non-glazed) surfaces in the image. A second option pipeline to falsecolor can plot isocontours on the original image above. See the falsecolor manpage (http://radsite.lbl.gov/radiance/man_html/falsecolor.1.html <http://radsite.lbl.gov/radiance/man_html/falsecolor.1.html>) for details.  
> 
> 
> 
> On Fri, Feb 12, 2016 at 7:02 AM, raghuram kalyanam <raghuram.kalyanam at bauing.uni-kl.de <mailto:raghuram.kalyanam at bauing.uni-kl.de>> wrote:
> 
> Hi Everyone,
> 
> I would like to know which is the best way to measure illuminance at certain view points in the room (radiance generated picture)  below. Let me also know which tools gives what kinds of results.
> 
> <scene_Scene_3.jpeg>
> 
> 
> Thanks & Regards,
> Raghu
> 
> 
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