[Radiance-general] RE: 60Watt bulb comparison
Anthony J. Farrell
anthony.farrell at dit.ie
Wed Jun 30 20:46:50 CEST 2004
John
Thanks for the useful info.
I had to construct a small black box (0.5 cube) for calibrating electronic
sensors I am currently using to monitor a full scale light pipe
installation, which in turn will be compared with a Radiance model thereof.
Furthermore, Recent research (Maamari et al. 2003) shows that a cube dark
box with an
opening central to one of the walls is most appropriate for simulation
modelling
comparison because reflectance values are minimal and easily measured, and
modelling complexities and associated anomalies are minimised. Conventional
modelling architectural black/white card display board. The reflectance
value for black mounting board was measured by Cannon-Brookes (1996) and is
quoted at 8.5%. A standard 60W incandescent light bulb was also fitted to
the dark box to fit into the recessed aperture, and was made removable for
daylight monitoring whereby the recessed aperture acted as a window or sky
light (without glass). I take your points though, that scale will influence
the final results, and in absence of good data for the GE 60W standard light
bulb I am using, its not good scientific comparison.
Anyway, I am more interested in the accuracy of the program with respect to
*daylight* rather than electric lighting. To date, I can only locate your
own work to the accuracy of the Radiance accuracy with daylight (as in the
RwR manual)...
Just on this point....does anyone know of any other references that have
compared daylight measurements with Radiance? would be great to include them
in my literature review.
It would be nice to model this simple box I have constructed in two
positions = recessed roof light, and recessed side window, facing each
orientation on overcast and sunny days. I could then create the model of the
box to scale (1=1) in Radiance and compare results with monitored values on
the roof of the campus building here in Dublin. What do you think about
this? or can you suggest some ways of enhancing the tests?
Kind Regards,
Anthony
Dublin Institute of Technology
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Today's Topics:
1. RE: 60Watt bulb luminaries data (Anthony J. Farrell)
2. RE: 60Watt bulb luminaries data (John Mardaljevic)
3. RE: 60Watt bulb luminaries data (Martin Moeck)
4. Re: colorpict and materials (Lars O. Grobe)
----------------------------------------------------------------------
Message: 1
Date: Wed, 30 Jun 2004 12:42:55 +0100
From: "Anthony J. Farrell" <anthony.farrell at dit.ie>
Subject: [Radiance-general] RE: 60Watt bulb luminaries data
To: radiance-general at radiance-online.org
Message-ID: <OJEGILOIGGNAEAODNHIIEEHBCDAA.anthony.farrell at dit.ie>
Content-Type: text/plain; charset=us-ascii
I am currently carrying out basic validation techniques of the Radiance
software using a black box and standard 60Watt bulb therein.
I cannot locate a standard incandescent 60W bulb (just bare hung from
ceiling, no lamp shade) on the desktop radiance program.
Can anyone help me by way of an add on file for a standard light bulb (even
if not 60W!) or refer me to a suitable IESNA file?
Kind regards
Anthony
-----Original Message-----
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Sent: 30 June 2004 10:59
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Subject: Radiance-general Digest, Vol 4, Issue 25
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Today's Topics:
1. Re: Illuminance calculation on a virtual surface? (gward at lmi.net)
2. Re: colorpict and materials (Lars O. Grobe)
3. Re: colorpict and materials (Jack de Valpine)
----------------------------------------------------------------------
Message: 1
Date: Tue, 29 Jun 2004 04:18:48 -0700
From: gward at lmi.net
Subject: Re: [Radiance-general] Illuminance calculation on a virtual
surface?
To: rpg at rumblestrip.org, Radiance general discussion
<radiance-general at radiance-online.org>
Message-ID: <1088507928.40e1501822b7c at webmail.lmi.net>
Content-Type: text/plain; charset=ISO-8859-1
OK, Rob -- you got me. Your little trick would work. I don't think he
really needs it, though, since he already has a method for generating
the grid points for rtrace. He can simply increase the resolution of
the grid he already has (as Raphael suggested) and/or upsample the
result using pfilt. Or your method. All will work.
-Greg
Quoting Rob Guglielmetti <rpg at rumblestrip.org>:
> Hi Greg, Hi John,
>
> Greg Ward wrote:
>
> > No good. Trans gets ignored by the rpict -i option. Just use pfilt to
> > scale the illuminance map if it's not big enough. (John M's suggestion
> > -- he's sitting next to me in Leicester.)
>
> Oh yeah? =8-p
>
> vwrays -x XRES -y YRES -vf viewfile -fd | rtrace -h -fd -opn octree \
> | rtrace -fdc -I render_options -x XRES -y YRES octree > illum_picture.pic
>
> Greg, does this look familiar? A little ditty from a year or so ago?
> You sent me this tip when I asked you how to get illuminance on a
> building's curtain wall. The first rtrace computes the intersection
> point (which is fast) and the second rtrace does the illuminance
> calculation. Cool, yes? Yes.
>
> Now, given this little tip, could he use trans as I described?
>
------------------------------
Message: 2
Date: Tue, 29 Jun 2004 14:34:03 +0300
From: Lars O. Grobe <grobe at gmx.net>
Subject: Re: [Radiance-general] colorpict and materials
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <38C05080-C9C0-11D8-ACAF-000A959DDB22 at gmx.net>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi,
sorry, so again, I try to be clear in asking this time ;-) By the way,
have nice holidays (I hope that's the reason for your travel ;-)!
All is about the question how to map pictures onto a surface without
corrupting its material properties. I understand that colorpict
multiplies the material color components with those of the picture.
If I have a grayscale image processed by normpat (which means that the
average gray value is 1.0) and apply it to a material, the overall
color and brightness will remain the same. So I get the "pattern" from
the image, but the surface still has the correct material properties
(color, brightness etc). I used this so far.
Now I want to use a colored picture for mapping. I also apply normpat
to it, so, as far as I understand, the average of all R, G and B must
be 1.0, right? For example, I use a normpat'ed picture of green marble.
I than apply this using colorpict to a surface, which has a "marble"
material. Will the overall color and brightness still be that of the
defined material, as the picture map has the average of 1.0?
The background: I try to use exact data for material definitions, but
the image maps can't all be color corrected. So I want the overall
color and brightness from defined materials, e.g. from the plastic
material, and use the map only for what I would call "local color
variation". The reason is that I have e.g. red marble, got its color,
brightness and all that defined as plastic marble. But the marble has
blue particles which won't appear if I use a grayscale imagemap. So I
want to use a normpat'ed (NOT colorcorrected e.g. by macbethcal!) to
bring these blue parts onto the surface. The whole surface however must
still have the average color of my plastic marble material.
If I understand the man-page of normpat, that's just what it was
invented for. However, I am a bit unsure, as all Radiance documentation
uses colorpict with a bright white material.
TIA+CU, Lars.
--
Lars O. Grobe
grobe at gmx.net
------------------------------
Message: 3
Date: Tue, 29 Jun 2004 09:38:59 -0400
From: Jack de Valpine <jedev at visarc.com>
Subject: Re: [Radiance-general] colorpict and materials
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <40E170F3.9040504 at visarc.com>
Content-Type: text/plain; charset="us-ascii"
Hi Lars,
I believe that what you need to do is take your colorpict modifier and
apply it to a material such as a plastic that uses the reflectance of
your material sample as the rgb parameters. I believe that you DO want
to use macbethcal to callibrate the color values of the image and
determine an estimated reflectance. Then using normpat on the image will
move the values in image so the average is 1.0.
So steps as follows:
1. acquire sample material image by photography, scan....
2. callibrate sample image with macbethcal
3. use callibrated sample image to estimate average color
4. calculate reflectance based on average color values, grey(r,g,b)
5. normpat the callibrated image
Then create material as follows:
void colorpict color.image.pattern
7 red green blue <normpat picture>.pic picture.cal Px Py
0
1 <aspect>
color.image.pattern plastic color.image.material
0
0
5 <grey(r,g,b)> <grey(r,g,b)> <grey(r,g,b)> <s> <r>
Since the colorpict is normalized to an average value of one, it will
modify the plastic around the reflectance of the plastic. For example,
if colorpict returns 1.1 for red then the red of the plastic will be 10%
brighter.
In short I think that there are two main ways to use colorpict
1. final reflectance set by colorpict image - colorpict is used to
set final reflectance of material, that is use callibrated image
colorpict modifier and material with reflectance of 1.0
2. final reflectance set by base material - colorpict is used to
modify reflectance set by material, that is normpat image
colorpict modifier is used to modify reflectance set by material
I hope this is helpful.
Regards,
-Jack
Lars O. Grobe wrote:
> Hi,
>
> sorry, so again, I try to be clear in asking this time ;-) By the way,
> have nice holidays (I hope that's the reason for your travel ;-)!
>
> All is about the question how to map pictures onto a surface without
> corrupting its material properties. I understand that colorpict
> multiplies the material color components with those of the picture.
>
> If I have a grayscale image processed by normpat (which means that the
> average gray value is 1.0) and apply it to a material, the overall
> color and brightness will remain the same. So I get the "pattern" from
> the image, but the surface still has the correct material properties
> (color, brightness etc). I used this so far.
>
> Now I want to use a colored picture for mapping. I also apply normpat
> to it, so, as far as I understand, the average of all R, G and B must
> be 1.0, right? For example, I use a normpat'ed picture of green
> marble. I than apply this using colorpict to a surface, which has a
> "marble" material. Will the overall color and brightness still be that
> of the defined material, as the picture map has the average of 1.0?
>
> The background: I try to use exact data for material definitions, but
> the image maps can't all be color corrected. So I want the overall
> color and brightness from defined materials, e.g. from the plastic
> material, and use the map only for what I would call "local color
> variation". The reason is that I have e.g. red marble, got its color,
> brightness and all that defined as plastic marble. But the marble has
> blue particles which won't appear if I use a grayscale imagemap. So I
> want to use a normpat'ed (NOT colorcorrected e.g. by macbethcal!) to
> bring these blue parts onto the surface. The whole surface however
> must still have the average color of my plastic marble material.
>
> If I understand the man-page of normpat, that's just what it was
> invented for. However, I am a bit unsure, as all Radiance
> documentation uses colorpict with a bright white material.
>
> TIA+CU, Lars.
> --
> Lars O. Grobe
> grobe at gmx.net
>
>
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
--
# John E. de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction
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Message: 2
Date: Wed, 30 Jun 2004 14:32:15 +0100 (BST)
From: John Mardaljevic <jm at dmu.ac.uk>
Subject: [Radiance-general] RE: 60Watt bulb luminaries data
To: radiance-general at radiance-online.org
Message-ID: <E1BffCB-0007OY-00 at saturn.dmu.ac.uk>
Content-Type: TEXT/plain; charset=us-ascii
Anthony,
Wait a moment whilst the spots before my eyes subside. Ah, that's better.
> I am currently carrying out basic validation techniques of the Radiance
> software using a black box and standard 60Watt bulb therein.
>
> I cannot locate a standard incandescent 60W bulb (just bare hung from
> ceiling, no lamp shade) on the desktop radiance program.
>
> Can anyone help me by way of an add on file for a standard light bulb
(even
> if not 60W!) or refer me to a suitable IESNA file?
The results you get are likely to depend on the size of the box
and the type of lamp, not to mention a few other factors.
You could model the bulb as a luminous sphere. But you'd have to know
what the luminance of the bulb was. Also, a sphere light source is not
subdivided, i.e. it is sampled by a single ray (p511 RwR). Which may
cause problems if the box is small compared to the bulb. A 'frosted'
or pearl bulb may have a largely isotropic luminous output, provided you
don't see too much of the (luminous) shank where it connects to the
socket. Any measured output distribution (say, IENSA) would, I guess,
be sensitive to the type of lamp. And it would assume a 'point source'
distribution, even though you would model it as, say, a disc or polygon.
Squinting at my desk lamp through a pinched-finger aperture (hence the
spots) revealed that the uniform luminance of the pearl bulb was an
illusion - much of the output of the bulb is from around the filament.
In sort, I suspect that any comparison between measurement and predictions
for your bulb & box will say much about the precision of the photometry,
maybe a little bit about the limitations of single ray light source
sampling,
and not much at all about the intrinsic accuracy of Radiance for realistic
architectural scenarios (electric or daylighting). The direct light source
calculation for small angular light sources (e.g. 'spherical' bulb from
several feet away with no occlusion) is pretty much a 'no brainer' and
Radiance will give a result that is near as dammit to the exact solution.
When you get close up to a non-ideal bulb however, then it's a matter of
getting the photometry right.
-John
-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
jm at dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
------------------------------
Message: 3
Date: Wed, 30 Jun 2004 12:07:27 -0400
From: "Martin Moeck" <MMoeck at engr.psu.edu>
Subject: [Radiance-general] RE: 60Watt bulb luminaries data
To: "Radiance general discussion"
<radiance-general at radiance-online.org>
Message-ID:
<84F05BA9118BBD4A8FC6409808CE266C113AE1 at ENGRMAIL2.engr.psu.edu>
Content-Type: text/plain; charset="utf-8"
Anthony,
You can download an IES photometric file for a PAR 60W incandescent narrow
flood from Osram Sylvania at
www.personal.psu.edu/mum13/60PAR30.CAP.NFL25.ies
<http://www.personal.psu.edu/mum13/60PAR30.CAP.NFL25.ies>
Use "ies2rad 60PAR30.CAP.NFL25.ies"
This will create the file "60PAR30.CAP.NFL25.rad" in metric units (meters).
I never saw photometric files for simple incandescent lamps.
I am currently running a fairly accurate simulation in AGI32 V1.7, which
will complete in 3 hours for a simple empty box 3X3X3 meters and one PAR
lamp.
Martin Moeck, Penn State
-----Original Message-----
From: Anthony J. Farrell [mailto:anthony.farrell at dit.ie]
Sent: Wed 6/30/2004 7:42 AM
To: radiance-general at radiance-online.org
Cc:
Subject: [Radiance-general] RE: 60Watt bulb luminaries data
I am currently carrying out basic validation techniques of the Radiance
software using a black box and standard 60Watt bulb therein.
I cannot locate a standard incandescent 60W bulb (just bare hung from
ceiling, no lamp shade) on the desktop radiance program.
Can anyone help me by way of an add on file for a standard light bulb (even
if not 60W!) or refer me to a suitable IESNA file?
Kind regards
Anthony
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Message: 4
Date: Wed, 30 Jun 2004 20:06:58 +0300
From: Lars O. Grobe <grobe at gmx.net>
Subject: Re: [Radiance-general] colorpict and materials
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <E5788A0C-CAB7-11D8-9111-000A959DDB22 at gmx.net>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Jack,
thank You for the reply.
> 2. final reflectance set by base material - colorpict is used to
> modify reflectance set by material, that is normpat image colorpict
> modifier is used to modify reflectance set by material
I want to do this, I have the material values, the colorpict is just to
add some visual credibility ;-) But I also want to have the final
overall (that means the average over the whole surface, like selecting
an area in ximage vs. a point) color from the base material.
> So steps as follows:
>
> 1. acquire sample material image by photography, scan....
> 2. callibrate sample image with macbethcal
> 3. use callibrated sample image to estimate average color
> 4. calculate reflectance based on average color values, grey(r,g,b)
> 5. normpat the callibrated image
So, if I already have the rgb for the base material (which is plastic),
do I really have to calibrate (macbethcal) the picture map?
Maybe I show you an example:
--
# porphyry red 1: values from ximage and macbethcal'ed pic
void plastic porphyry_red_1
0
0
5 .09 .06 .05 .02 0
# non-calibrated normpat'ed pic
void colorpict sophia_porphyry_red_1_pattern
13 noop noop noop sophia_porphyry_red_1.pic picture.cal tile_u tile_v
-s .2 -rx 90 -rz 90
0
0
# give alias the modifier as output from dxf2rad
sophia_porphyry_red_1_pattern alias l_porphyry_red_1 porphyry_red_1
--
Will this be correct?
TIA, CU Lars.
--
Lars O. Grobe
grobe at gmx.net
------------------------------
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