[Radiance-general] rtrace direction

[Andrew McNeil]

Vaib,

There is an important difference between the -i (lower case i) and -I
(capital i) in rtrace.   When -i is given, rtrace will trace a ray in the
direction given, and then will calculate the hemispherical irradiance at
the point where the ray intersects with geometry (ignoring some material
types).  With the -I command it calculates the hemispherical irradiance at
the point you specify using the direction vector as a a normal for the
imaginary surface on which irradiance is calculated.

Users typically want -I, except for specialized cases.  You should make
sure that  -i is correct for your case.

Andy




On Mon, Apr 22, 2013 at 4:44 AM, Vaib <vaibhavjain.co at gmail.com> wrote:

> Thanks Lars. Actually my illuminance sensor (I already used -I switch),
> was spatially located on a wall, with its direction towards a window Xorg
> Yorg Zorg 0 -1 0. But out of this window there was no sky glow or source
> defined (neither ground); only Sun source was defined. Thats why, the
> sensor was not able to trace any ray coming from that direction (0 -1 0)
> using rtrace, because there was no sky. But finally I understood that and
> the issue is now resolved. Also this proved to me that there is some
> reverse ray tracing going on. :)
>
> This was my command: echo '3 4 1.5 0 -1 0' | rtrace -w -as 512 -ar 512
> -aa 0.15 -ab 2 -i+ -h sunnyScene.oct | rcalc -e
> '$1=($1*.265+$2*.67+$3*.065)*179'
>
> Thanks again!
>
> Vaib
>
> PS: If you are interested to see the geometry, and sky, I have reported
> that in my university assignment. Just see the 'last page' of this report:
> http://tinyurl.com/d86dbo4
>
>
>
>
>
> Best regards,
> Vaibhav Jain
> www.vaibhavjain.co
>
>
>
>
>
> On 21 April 2013 23:56, Lars O. Grobe <grobe at gmx.net> wrote:
>
>> Hi Vaibhav,
>>
>> it is hard to tell what caused the result, as we do not know the
>> parameters you used with rtrace. For the point to be interpreted as an
>> irradiance sensor, which seams to be what you expect, you need the -I
>> switch at least.
>>
>> Cheers, Lars.
>>
>> > Hello again!
>> >
>> > By doing some parametric analysis I got my answer. Actually my so called
>> > photocell was facing the window, and since I had no sky distribution
>> > (only sun defined in my sky file), thats why in the model there was no
>> > sky environment (just like in outer Space). Hence the recieved
>> > irradiance at that location was Zero. I think I am right now.
>> >
>> > Thanks!
>> >
>> > Best regards,
>> > Vaibhav Jain
>>
>>
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>
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