Modeling Question for Translucent Glass

Hi,

I am fairly new to Radiance and was trying to model a interior translucent
glazing (possibly a ceramic frit). I have looked up the archive posts for
help but need a little bit more guidance on the modeling of the glazing. I
am modeling the white translucent glazing with about 50% transmittance using
the following parameters:

void trans translucent panel
0
0
7 1 1 1 0 0 0.5 0.2

I would like to know if I am correct in my assumptions.

The second issue which I have not been able to figure out is how to show
this trans material inside the space in the final rendering in Radiance as
it is essentially invisible.

Any help on this will be appreciated.

Regards,
Nik

I am fairly new to Radiance and was trying to model a interior translucent glazing

void trans translucent panel

0

0

7 1 1 1 0 0 0.5 0.2

One obvious error is the name 'translucent panel'. Identifiers can not contain
spaces so it should be 'translucent_panel' or something like that.

The '1 1 1' looks odd to me. I don't think that's actually a physical material.
I'd go for something like 0.8 for white.

The second issue which I have not been able to figure out is how to show this trans material inside the space in the final rendering in Radiance as it is essentially invisible.

Think about it:
if it's 50% translucent it has to be visible (even glass with 50% transmission would
show as a darker shade of the room behind it.) You're talking about 'white' so I assume
that you do want some amount of scattering of the light. In fact, the material above
scatters 80% of the light that passes, so it would definitely be visible.

Just try a simple scene with a test cube and a bit of ground below and use
the command 'objview' (Unix only) to see how the material works out.

Regards,
Thomas

···

On 12 Jun 2008, at 17:50, Nikhil Kapur wrote:

A thought about rendering as "invisible" ...

Nik, Is it invisible in any rendering, or only if you render an
illuminance image with the -i option?

···

________________________________

From: radiance-general-bounces@radiance-online.org
[mailto:radiance-general-bounces@radiance-online.org] On Behalf Of
Thomas Bleicher
Sent: Thursday, 12 June, 2008 6:03 PM
To: Radiance general discussion
Subject: Re: [Radiance-general] Modeling Question for Translucent Glass

On 12 Jun 2008, at 17:50, Nikhil Kapur wrote:

  I am fairly new to Radiance and was trying to model a interior
translucent glazing

  void trans translucent panel

  0

  0

  7 1 1 1 0 0 0.5 0.2

One obvious error is the name 'translucent panel'. Identifiers can not
contain
spaces so it should be 'translucent_panel' or something like that.

The '1 1 1' looks odd to me. I don't think that's actually a physical
material.
I'd go for something like 0.8 for white.

  The second issue which I have not been able to figure out is how
to show this trans material inside the space in the final rendering in
Radiance as it is essentially invisible.

Think about it:
if it's 50% translucent it has to be visible (even glass with 50%
transmission would
show as a darker shade of the room behind it.) You're talking about
'white' so I assume
that you do want some amount of scattering of the light. In fact, the
material above
scatters 80% of the light that passes, so it would definitely be
visible.

Just try a simple scene with a test cube and a bit of ground below and
use
the command 'objview' (Unix only) to see how the material works out.

Regards,
Thomas
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

Hi Nikhil,

As Thomas said in his response, the material should show up in a normal rendering. The best way to model frit glass is to use the "glaze.csh" script that I created with funding from Visarc. For a single-pane glazing using a full covering of V-175 white frit, this script produces:

···

############################################
# Glazing produced by Radiance glaze script
# $Revision: 2.7 $
# Material surface normal points to interior
# Number of panes in system: 1
# Exterior surface s1 type: clear glass
# Interior surface s2 type: V-175 white frit
# s2 coating coverage: 1
# Exterior normal hemispherical reflectance: 0.33
# Interior normal hemispherical reflectance: 0.59
# Normal hemispherical transmittance: 0.21
#
void BRTDfunc glaze1_unnamed
10
         sr_frit_r sr_frit_g sr_frit_b
         st_frit_r st_frit_g st_frit_b
         0 0 0
         glaze1.cal
0
11
0.59
0.256
0.253
0.251
0.21
         -1 1

Try this for now, or run the script yourself to vary the parameters. If you can't run the script because you only have a Windows machine, then you may be stuck playing around with the "trans" material.

-Greg

From: "Nikhil Kapur" <nkapur@ctgenergetics.com>
Date: June 12, 2008 3:14:17 PM PDT
Hi Greg,

I had a question for modeling in Radiance. I apologize for emailing to you directly. I have posted it on the radiance forum today morning as well, but had not seen any responses and I have a deadline to meet.

Since I am fairly new to Radiance I was trying to model an interior translucent glazing (possibly a frit on the glazing). I looked up the archive posts for help but needed a little bit more guidance on the modeling of the glazing. I am using ECOTECT for the basic geometry and ECOTECT’s Radiance Panel to interface with Radiance.

I am modeling a white translucent glazing with about 50% transmittance using the following parameters:

void trans translucent panel

0

0

7 1 1 1 0 0 0.5 0.2

I would like to know if I am correct in my assumptions or if there is some other way to model a translucent / frit glass (any resources on the web that I can look up)

Additionally, I have not been able to figure how to show this trans material inside the space in the final rendering in Radiance as it is essentially invisible. I was reading up on the illum material type but could not figure out how to apply it to this translucent glazing.

Any help on this will be appreciated.

Thanks.

Nikhil Kapur

CTG Energetics, Inc

9 4 9 . 4 2 8 . 6 2 7 1

I really appreciate the responses from all you folks.

Chris the trans panel was invisible in the illuminance run and showed up in
the Luminance run. Thanks for pointing that out.

Regards,
Nikhil

Chris I tried it both ways using with and without the -I command
I am using the window binaries and am running the simulation using ECOTECT's
Radiance Control Panel. The

···

2008/6/12 <radiance-general-request@radiance-online.org>:

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Today's Topics:

  1. Re: oconv and rtrace_dc warnings for non-planar vertices
     (Thomas Bleicher)
  2. Re: oconv and rtrace_dc warnings for non-planar vertices
     (Greg Ward)
  3. Re: Modeling Question for Translucent Glass (Thomas Bleicher)
  4. RE: Modeling Question for Translucent Glass (Christopher Rush)
  5. Re: Modeling Question for Translucent Glass (Greg Ward)

---------- Forwarded message ----------
From: Thomas Bleicher <tbleicher@arcor.de>
To: Radiance general discussion <radiance-general@radiance-online.org>
Date: Thu, 12 Jun 2008 20:16:05 +0100
Subject: Re: [Radiance-general] oconv and rtrace_dc warnings for non-planar
vertices

On 11 Jun 2008, at 21:24, Ramana Koti wrote:

oconv: warning - non-planar verterx for polygon "f_1719_0" (this happens

for 20 or so polygons)
rtrace_dc: warning - non-planar vertex for polygon "F_1636 (Can't see the
rest of it, this happens for probably the same polygons but not in the same
order)

I used the SketchUp to Radiance su2rad plugin to export geometry from a
sketchup model and I had to start the simulation before DAYSIM refreshed
geometry display since it was taking too long to do that.

How serious are these warnings and why are they occuring?

The export of polygons from Sketchup has only a limited accuracy. This
results in some
cases in polygons where one of the points is outside of the plane defined
by the rest
of the vertices. Radiance has a built in tolerance for these points but
when that's exceeded
the warning is generated and the vertex or the whole polygon ignored in the
rendering.
I'm not sure about the last part but maybe someone else knows better.

Relevance: If the polygon is ignored and it is essential for the geometry
(ie a wall of a room)
then it is relevant. If it's just a tiny piece that doesn't do much for the
lighting it's harmless.

To avoid this problem export with the option 'triangulate'. This creates
polygons with
only 3 vertices. Much more polygons in the scene but no warnings.

Regards,
Thomas

---------- Forwarded message ----------
From: Greg Ward <gregoryjward@gmail.com>
To: Radiance general discussion <radiance-general@radiance-online.org>
Date: Thu, 12 Jun 2008 14:40:22 -0700
Subject: Re: [Radiance-general] oconv and rtrace_dc warnings for non-planar
vertices
The warnings don't indicate any action, and are only given by Radiance
because cracks may appear between polygons due to the determination of an
"average plane" that doesn't pass exactly through every point.

-Greg

From: Thomas Bleicher <tbleicher@arcor.de>

Date: June 12, 2008 12:16:05 PM PDT

On 11 Jun 2008, at 21:24, Ramana Koti wrote:

oconv: warning - non-planar verterx for polygon "f_1719_0" (this happens

for 20 or so polygons)
rtrace_dc: warning - non-planar vertex for polygon "F_1636 (Can't see the
rest of it, this happens for probably the same polygons but not in the same
order)

I used the SketchUp to Radiance su2rad plugin to export geometry from a
sketchup model and I had to start the simulation before DAYSIM refreshed
geometry display since it was taking too long to do that.

How serious are these warnings and why are they occuring?

The export of polygons from Sketchup has only a limited accuracy. This
results in some
cases in polygons where one of the points is outside of the plane defined
by the rest
of the vertices. Radiance has a built in tolerance for these points but
when that's exceeded
the warning is generated and the vertex or the whole polygon ignored in
the rendering.
I'm not sure about the last part but maybe someone else knows better.

Relevance: If the polygon is ignored and it is essential for the geometry
(ie a wall of a room)
then it is relevant. If it's just a tiny piece that doesn't do much for
the lighting it's harmless.

To avoid this problem export with the option 'triangulate'. This creates
polygons with
only 3 vertices. Much more polygons in the scene but no warnings.

Regards,
Thomas

---------- Forwarded message ----------
From: Thomas Bleicher <tbleicher@arcor.de>
To: Radiance general discussion <radiance-general@radiance-online.org>
Date: Thu, 12 Jun 2008 23:03:00 +0100
Subject: Re: [Radiance-general] Modeling Question for Translucent Glass

On 12 Jun 2008, at 17:50, Nikhil Kapur wrote:

I am fairly new to Radiance and was trying to model a interior translucent
glazing

void trans translucent panel

0

0

7 1 1 1 0 0 0.5 0.2

One obvious error is the name 'translucent panel'. Identifiers can not
contain
spaces so it should be 'translucent_panel' or something like that.

The '1 1 1' looks odd to me. I don't think that's actually a physical
material.
I'd go for something like 0.8 for white.

The second issue which I have not been able to figure out is how to show
this trans material inside the space in the final rendering in Radiance as
it is essentially invisible.

Think about it:
if it's 50% translucent it has to be visible (even glass with 50%
transmission would
show as a darker shade of the room behind it.) You're talking about 'white'
so I assume
that you do want some amount of scattering of the light. In fact, the
material above
scatters 80% of the light that passes, so it would definitely be visible.

Just try a simple scene with a test cube and a bit of ground below and use
the command 'objview' (Unix only) to see how the material works out.

Regards,
Thomas

---------- Forwarded message ----------
From: "Christopher Rush" <Christopher.Rush@arup.com>
To: "Radiance general discussion" <radiance-general@radiance-online.org>
Date: Thu, 12 Jun 2008 18:16:22 -0400
Subject: RE: [Radiance-general] Modeling Question for Translucent Glass
A thought about rendering as "invisible" ..

Nik, Is it invisible in any rendering, or only if you render an illuminance
image with the -i option?

------------------------------
*From:* radiance-general-bounces@radiance-online.org [mailto:
radiance-general-bounces@radiance-online.org] *On Behalf Of *Thomas
Bleicher
*Sent:* Thursday, 12 June, 2008 6:03 PM
*To:* Radiance general discussion
*Subject:* Re: [Radiance-general] Modeling Question for Translucent Glass

On 12 Jun 2008, at 17:50, Nikhil Kapur wrote:

I am fairly new to Radiance and was trying to model a interior
translucent glazing

void trans translucent panel

0

0

7 1 1 1 0 0 0.5 0.2

One obvious error is the name 'translucent panel'. Identifiers can not
contain
spaces so it should be 'translucent_panel' or something like that.

The '1 1 1' looks odd to me. I don't think that's actually a physical
material.
I'd go for something like 0.8 for white.

The second issue which I have not been able to figure out is how to show
this trans material inside the space in the final rendering in Radiance as
it is essentially invisible.

Think about it:
if it's 50% translucent it has to be visible (even glass with 50%
transmission would
show as a darker shade of the room behind it.) You're talking about 'white'
so I assume
that you do want some amount of scattering of the light. In fact, the
material above
scatters 80% of the light that passes, so it would definitely be visible.

Just try a simple scene with a test cube and a bit of ground below and use
the command 'objview' (Unix only) to see how the material works out.

Regards,
Thomas

____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses

---------- Forwarded message ----------
From: Greg Ward <gregoryjward@gmail.com>
To: "Nikhil Kapur" <nkapur@ctgenergetics.com>
Date: Thu, 12 Jun 2008 15:35:38 -0700
Subject: [Radiance-general] Re: Modeling Question for Translucent Glass
Hi Nikhil,

As Thomas said in his response, the material should show up in a normal
rendering. The best way to model frit glass is to use the "glaze.csh"
script that I created with funding from Visarc. For a single-pane glazing
using a full covering of V-175 white frit, this script produces:

############################################
# Glazing produced by Radiance glaze script
# $Revision: 2.7 $
# Material surface normal points to interior
# Number of panes in system: 1
# Exterior surface s1 type: clear glass
# Interior surface s2 type: V-175 white frit
# s2 coating coverage: 1
# Exterior normal hemispherical reflectance: 0.33
# Interior normal hemispherical reflectance: 0.59
# Normal hemispherical transmittance: 0.21
#
void BRTDfunc glaze1_unnamed
10
       sr_frit_r sr_frit_g sr_frit_b
       st_frit_r st_frit_g st_frit_b
       0 0 0
       glaze1.cal
0
11
0.59
0.59
0.59
0.256
0.253
0.251
0.21
0.21
0.21
       -1 1

Try this for now, or run the script yourself to vary the parameters. If
you can't run the script because you only have a Windows machine, then you
may be stuck playing around with the "trans" material.

-Greg

From: "Nikhil Kapur" <nkapur@ctgenergetics.com>

Date: June 12, 2008 3:14:17 PM PDT
Hi Greg,

I had a question for modeling in Radiance. I apologize for emailing to you
directly. I have posted it on the radiance forum today morning as well, but
had not seen any responses and I have a deadline to meet.

Since I am fairly new to Radiance I was trying to model an interior
translucent glazing (possibly a frit on the glazing). I looked up the
archive posts for help but needed a little bit more guidance on the modeling
of the glazing. I am using ECOTECT for the basic geometry and ECOTECT's
Radiance Panel to interface with Radiance.

I am modeling a white translucent glazing with about 50% transmittance
using the following parameters:

void trans translucent panel

0

0

7 1 1 1 0 0 0.5 0.2

I would like to know if I am correct in my assumptions or if there is some
other way to model a translucent / frit glass (any resources on the web that
I can look up)

Additionally, I have not been able to figure how to show this trans
material inside the space in the final rendering in Radiance as it is
essentially invisible. I was reading up on the illum material type but could
not figure out how to apply it to this translucent glazing.

Any help on this will be appreciated.

Thanks.

Nikhil Kapur

CTG Energetics, Inc

9 4 9 . 4 2 8 . 6 2 7 1

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Radiance-general@radiance-online.org
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