[Radiance-general] Measuring Illuminance

[Axel Jacobs]

Raghu,

there is a short section on the use of the rad command in my Radiance
Tutorial (Section 6).
For ximage and illuminance readings, please see Chapter 5.5 in my
Radiance Cookbook.
Both documents are available on Jaloxa:
http://www.jaloxa.eu/resources/radiance/documentation/index.shtml

Regards

Axel

On 17 February 2016 at 07:16, Raghuram Kalyanam <kalyanam at rhrk.uni-kl.de> wrote:
> Thanks Greg.
>
> I have a weird problem, I tried to execute this earlier
>
> rad scene.rif & it creates a process and then kills instantly.
>
> where as
>
> rad -o x11 scene.rif   works normal.
>
> Any reason why this could happen. I am using a Macbook pro, can this occur
> because of lack of memory ??
>
> Best Regards,
> Raghu
>
> On Feb 17, 2016, at 12:31 AM, Greg Ward <gregoryjward at gmail.com> wrote:
>
> Your ampersand is in the wrong place -- it needs to go at the end of the
> command.  The following should work:
>
> rad scene.rif "render=-i" &
>
> The quotes aren't strictly necessary, but allow you to put spaces and
> multiple options into the render variable.
>
> You can also add the render variable directly to your scene.rif file.
>
> Cheers,
> -Greg
>
> From: Raghuram Kalyanam <kalyanam at rhrk.uni-kl.de>
> Subject: Re: [Radiance-general] Measuring Illuminance
> Date: February 16, 2016 3:21:41 PM PST
>
> Hi Greg,
>
> Please let me know how to use render here!! I tried
>
> rad scene.rif & render=-i
> rad scene.rif & render=rpict -i
> rad scene.rif & render='rpict -i'
>
> Nothing worked. Sorry for my ignorance. It would be help full  if you could
> let me how to use that.
>
> Is there anyway I could see the image in ximage and could know illuminance
> values for every pixel i hover or something similar.
>
> Best Regards,
> Raghu
>
> On Feb 16, 2016, at 8:52 PM, Greg Ward <gregoryjward at gmail.com> wrote:
>
> Hi Raghu,
>
> In the "rad" program, you may use the "render" variable to add the "-i"
> option needed for irradiance (illuminance) calculation.
>
> -Greg
>
> From: Raghuram Kalyanam <kalyanam at rhrk.uni-kl.de>
> Subject: Re: [Radiance-general] Measuring Illuminance
> Date: February 16, 2016 7:11:34 AM PST
>
> Hi Rob,
>
> Thanks for your reply. Could you elaborate on how to get irradiance image
> and convert that to illuminance using standard luminous efficacy.  I have
> tried using rpict as you said, but it turned out a radiance(luminance)
> image.
> I executed the below command.
>
> rpict -vf Views/Scene_3.vf -av .5 .5 .5 -i scene.oct | falsecolor | ximage
>
> (Basically I generated radiance pictures (previously) directly with rad, I
> guess rad calls rpict internally. But how could we pass -i argument  to
> rpict in this case!! So i guess the above command might have some problem)
>
> I got false-color image with a contours of luminance.
>
> Any way I wanted Luminance and Illuminance in numerical values for
> corresponding to the pixels. Could you help me how to approach, or may be
> with an example.
>
> Best Regards,
> Raghu
>
> On Feb 15, 2016, at 2:04 AM, 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) for details.
>
>
>
> On Fri, Feb 12, 2016 at 7:02 AM, raghuram kalyanam
> <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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