[Radiance-general] Three-Phase Method - subdivision of window with sensor located close to the window
Anne Iversen
iversen.anne at gmail.com
Fri Apr 29 05:32:23 PDT 2011
Thanks Greg, David and Andy for your replies.
Have run simulations with the glow material and find no significant
differences in sensor signal when having no subdivision compared to
different subdivisions. So I'll stick to the glow material for my window and
simulate without any window subdivision. Elegant ;-).
I have simply changed the window material from light to glow and set the
settings as recommended by Andy.
void glow windowlight
0
0
4 1 1 1 0
Best,
Anne
On Thu, Apr 28, 2011 at 9:00 PM, <
radiance-general-request at radiance-online.org> wrote:
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> Today's Topics:
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> 1. Re: Three-Phase Method - subdivision of window with sensor
> located close to the window (David Geisler-Moroder)
> 2. Re: Three-Phase Method - subdivision of window with sensor
> located close to the window (Greg Ward)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 28 Apr 2011 20:24:17 +0200
> From: David Geisler-Moroder <david.moroder at gmail.com>
> To: radiance-general at radiance-online.org
> Subject: Re: [Radiance-general] Three-Phase Method - subdivision of
> window with sensor located close to the window
> Message-ID: <4DB9B0D1.9000002 at gmail.com>
> Content-Type: text/plain; charset="windows-1252"; Format="flowed"
>
> Hi Anne,
>
> give Andy's suggestion using the glow material a try - I usually do that
> for large windows (i.e. in most cases) to avoid the
> subsampling problem of the "window lights". Even if you do not put
> sensors close to the window, you mostly have walls
> somewhere close to the window where the same issue arises.
> Manually subdividing is only necessary - as Andy states - if it's needed
> because of changes in the exterior illumination.
>
> Cheers,
> David
>
> Am 28.04.2011 19:38, schrieb Andy McNeil:
> > Hi Anne,
> >
> > On my computer the text on your charts show up as black squares. But
> > I think I can still provide some relevant advice.
> >
> > Generally speaking, subdivision of the window for the three phase
> > method is only necessary when there are nearby external obstructions
> > or for intermediary blind positions. But your case is unusual - your
> > sensor point is so very close to the window.
> >
> > When generating the view matrix we typically use a light material for
> > the window. Direct (deterministic) sampling is used to calculate the
> > window's contribution. The direct sampling algorithm will
> > automatically divide a light source according to the -ds parameter,
> > however the maximum number of divisions is limited to 64 (as
> > determined by the variable MAXSPARTS in source.h). Given the
> > proximity of your sensor to the window I don't think 64 direct samples
> > will accurately map the window's outgoing klems divisions to
> > illuminance contribution at your sensor. Manually subdividing the
> > window is one approach. Though rather than horizontal bands I'd
> > suggest a pattern of squares that is finer near the sensor and corse
> > away from the sensor (see ascii art below). You also want to set -dt
> > 0 and -dc 1.
> > ____________________
> > | |__|__|__| |
> > |______|__|__|__|______|
> > | | | |
> > |______|_______|______|
> >
> > Alternatively you could consider using ambient sampling to sample the
> > window. You could try using a glow material for the window and set
> > -ad 2000 or higher. Roughly half the initial ambient sample rays
> > would hit the window (because your sensor is nearly against the
> > window). -ab can be low and -lw should be less than 1/ad, probably
> > 1/ad^2. I've never tried this, so I don't know how well (or if)
> > it'll work.
> >
> > If it were me, I'd give the glow material a try. It seems much more
> > elegant and now that I think about it, it might be a better approach
> > for some spaces.
> >
> > Good luck,
> > Andy
> >
> >
> >
> >
> > On Apr 28, 2011, at 8:48 AM, Anne Iversen wrote:
> >
> >> Hi list - Hope you have time to give me some guidance here :-)
> >>
> >>
> >> My question is if any of you have any recommendations or thoughts on
> >> how I should or shouldn't subdivide the window?
> >>
> >>
> >> *Problem:*
> >>
> >> I have a scene with a sensor located close to the window. The window
> >> is placed in y=0.82, and the sensor is located in y=0.84, just behind
> >> the window. Due to the sensor location this close to the window I?m
> >> thinking I have to subdivide the window to get a correct sensor
> >> reading, especially when solar shading is included in my simulations.
> >>
> >>
> >> I have run simulations for 4 different cases with different
> >> subdivisions of the window. The transmission matrix is an .xml file
> >> generated with window6 for a clear window. Nothing special here, yet!
> >> In further simulations I?ll introduce solar shading.
> >>
> >> My simulation results show that the sensor signal differs with the
> >> different subdivisions.
> >>
> >> You can see the results and subdivision of window in this link:
> >> http://dl.dropbox.com/u/9713279/ThreePhaseMethod_Subdivision.pdf
> >>
> >> And my script if necessary, in this link:
> >> http://dl.dropbox.com/u/9713279/threephasemethod.bash
> >>
> >> Thanks in advance,
> >> Anne
> >> _______________________________________________
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> Message: 2
> Date: Thu, 28 Apr 2011 11:42:03 -0700
> From: Greg Ward <gregoryjward at gmail.com>
> To: Radiance general discussion <radiance-general at radiance-online.org>
> Subject: Re: [Radiance-general] Three-Phase Method - subdivision of
> window with sensor located close to the window
> Message-ID: <104EA5FC-5DBE-4667-A035-6F840055114C at lmi.net>
> Content-Type: text/plain; charset=us-ascii
>
> Hi Anne,
>
> I agree that you should try the glow window. If you are using the rsensor
> program as your script seems to indicate, rays will be distributed over the
> window independently from how you've defined it. Only the secondary bounces
> will care if it's a light source or a glow and whether it's subdivided, and
> those should not matter to the results. This leaves the puzzle of why your
> output varies so much in the first place.
>
> Have you tried generating hemispherical fisheye views from the sensor
> position under the different simulation conditions? This is always my
> favorite way of debugging such problems.
>
> Best,
> -Greg
>
> > From: David Geisler-Moroder <david.moroder at gmail.com>
> > Date: April 28, 2011 11:24:17 AM PDT
> >
> > Hi Anne,
> >
> > give Andy's suggestion using the glow material a try - I usually do that
> for large windows (i.e. in most cases) to avoid the
> > subsampling problem of the "window lights". Even if you do not put
> sensors close to the window, you mostly have walls
> > somewhere close to the window where the same issue arises.
> > Manually subdividing is only necessary - as Andy states - if it's needed
> because of changes in the exterior illumination.
> >
> > Cheers,
> > David
>
>
>
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> End of Radiance-general Digest, Vol 86, Issue 23
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