[Radiance-general] "Sensor Surfaces"

[Achim Geissler]

Thomas

that script-solution sounds quite interesting and what you describe as what
you did with it sounds more like what I am looking for. The multitude of
possible switches for rtrace is quite a challenge, though.

What I want to do is this: I have a large building with external shading
that has a non-trivial geometric form. This shading is to be opened (to a
certain degree) at a given azimuth only if no direct radiation which would
hit the facade can get past in this location. So the task is to let the sun
travel around the building and for each position of interest check if any
direct hits can be found on any surface of the building façade behind the
shading.

Your suggestion seems to imply that this should be possible with rtrace.
Does setting -dr 0 mean that only direct beams are considered by rtrace? Or
does one need a good combination of -ds, -dt and -dc? The sun is the only
"active" source of light. I would set reflection of all shading surfaces to
Zero.

I am not sure what your input example describes. Having the material names
of "hit" surfaces given would seem O.K. if this can be constrained to
"direct" only, as the goal is to have "no direct hit".

Regards
Achim


-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Thomas
Bleicher
Sent: Mittwoch, 25. November 2009 18:42
To: Radiance general discussion
Subject: Re: [Radiance-general] "Sensor Surfaces"

Achim.

I'm afraid I don't quite understand what you want to do.

On Wed, Nov 25, 2009 at 7:40 AM, Achim Geissler
<achim.geissler at intergga.ch> wrote:
> The 'falsecolor' sounds quite interesting, but as far as I can tell it
does
> not allow "automatic" evaluation, i.e. create a file / files that can be
> somehow scanned for "hit" or "no hit" per surface. My problem is, that
> visually evaluating images after the simulation does not seem practical
due
> to form / size / repetitions.

I recently implemented a script that checks for a hit and miss
of the sky at possible sun positions. I just used the rtrace output
option to produce the material name of the hit surface.

Example input:
0 0 0 0 0 1
0 0 0 0 1 1
0 0 0 1 1 1

Example output:
skyglow
grey_40
grey_40

If you use a unique material name you can afterwards parse the
output with a simple awk one-liner to get the number of hits. Is
that more what you need?

> And I'm afraid I didn't understand if the stencil method could really
help,
> but it seems evaluation (or result) is still a "picture" - again not a
"hit"
> or "no hit" information for a given surface.

The output is a picture if you want rtrace to produce a picture.
It only depends on the options for rtrace. The nice thing about
the stencil method is that it generates ray origins and directions
over a surface, instead of a fixed size grid.

> Something like
>
http://www.radiance-online.org/radiance-workshop7/Content/Augsburger/Germain
> AugsburgerPresentation.pdf, page 8, but with "continuous" and not
> "discrete" sensors that can be evaluated for hit-or-miss somehow is what I
> have in mind.

Stencil could create the x,y,z,dx,dy,dz coordinates but only
for one half of the cylinder (the one facing you). And the
resolution would degrade towards the edges.

Perhaps you could outline your problem. Someone might have
another idea.

Regards,
Thomas

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