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Hi Paul.<br>
<br>
Since a glow functions like a light source the material is sensitive to
the orientation of the normal for the "glowing" polygon geometry. Thus
when a glow material such as:<br>
<br>
void glow test.glow<br>
0<br>
0<br>
4 1 1 1 0<br>
<br>
is applied to a polygon, the "front" side of the polygon (eg, the
positive normal) will glow with a radiance of 1 (in the above case)
whereas the backside of the polygon (the negative normal) will appear
black. <br>
<br>
So in your case any polygons that appear black need to be re-oriented,
so they glow in the right direction. There are a couple of ways to
check and fix this. The way we usually check is to apply a glow
material to the selected geometry and then objview just the selected
geometry. This way we can do a quick visual check. Now if you are
lucky, all the geometry either points in the right direction or it does
not. If this is the case and all the geometry is black, then you can do:<br>
<br>
xform -I original_geometry.rad > original_geometry.flipped.rad<br>
<br>
This will flip the orientation of all the normals in
original_geometry.rad. If on the other hand there is a mix of glowing
and black polygons then you will have to go back into your modeling
application and figure out how to flip things either by rebuilding the
geometry or some other strategy. In Autocad (for example) 3dfaces that
are built in a clockwise manner will have the normal pointing out of
the clockwise face (I hope I am remembering this correctly).<br>
<br>
The fourth argument of a glow specifies a sphere of influence for the
glow, resulting in illumination localized within the specified radius
(the fourth argument is the radius in the model units within which the
glow will essentially act like a light). So in other words a glow can
actually be used to illuminate things. So you should be thoughtful
about how you specify this value, to little and things may not be
illuminated locally (if they need to be at all), to big and you
basically have another light source in the scene. I think that Andy
suggested you could break the scene down between interior electric
lighting and various daylighting scenarios, with results being the
combination of electric plus the desired daylighting. You can probably
go one step further and break out the glow related "lighting" and run
that separately. The thinking would be that this would allow you to
test and tune your glow materials if that makes sense.<br>
<br>
More generally there are a couple of other items to consider. By using
mkillum you have essentially "moved" the resulting light into the
space, because of this you may be able to use a lower -ab setting such
as -ab 1. On the other hand, if some of your illum surfaces span large
areas, you will need to set -ds (direct sampling) to subdivide these
surfaces essentially "spreading" the light out over the surface rather
than samping the middle of the polygon. You may also need to experiment
with -dj (direct jitter). <br>
<br>
I hope this helps.<br>
<br>
Regards,<br>
<br>
-Jack de Valpine<br>
<br>
Paul Chilton wrote:
<blockquote
cite="mid:63252a3e0905272041i775cf0aek3890e6f258f74c60@mail.gmail.com"
type="cite">
<div>Hi Rob, Andy,</div>
<div> </div>
<div>Thank you both for you suggestions. I've been concentrating on
getting the glow material to properly work first.</div>
<div> </div>
<div>I've looked at the Radiance reference manual and read the
description of glow. In my rad file I've made a new glow material:</div>
<div> </div>
<div><strong>void glow</strong> glowsurface<br>
0<br>
0<br>
4 0.898 0.898 0.898 50</div>
<div> </div>
<div>and I've changed the name of the polygon that I want to glow
from it's original surface name of 'plaster_insulated' to the name
specified above i.e. 'glowsurface'. However in my image the surface
appears to be black and I've tried changing the maxrad variable but
this hasn't had an effect. I've read what it says about maxrad but I'm
still unsure of what it is exactly and what the variable range is (is
it a 0-1?) and what a typical value is. <br>
</div>
<div>Could you please help?</div>
<div> </div>
<div>Regards,</div>
<div> </div>
<div>Paul.<br>
</div>
<div class="gmail_quote">On Wed, May 27, 2009 at 3:08 PM, Rob
Guglielmetti <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:rpg@rumblestrip.org">rpg@rumblestrip.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">
<div class="im"><br>
On May 26, 2009, at 8:07 PM, Paul Chilton wrote:<br>
<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Hi
Lars, Rob<br>
<br>
It looks like I have managed to get the mkillum surface to work for the
skylight. The render times are reduced and the images displayed look
different too.<br>
<br>
However, I have been testing the use of the mkillum without the
artificial lighting turned on in my model. When I do turn them on and
run them with the parameters set to high accuracy levels, the
simulation takes a very long time. I think that any time gained by the
mkillum surface is negated by the number of lights it has to simulate.<br>
</blockquote>
<br>
</div>
The simulations will increase as you increase the number of light
sources, that is a fact of life (or virtual life, as in this case). The
mkillum process will help improve the speed and accuracy of the
lighting simulation of the light filtering in from the skylight, but as
you add in complexity through electric light sources, you will
experience a delay in the simulation times, yes.
<div class="im"><br>
<br>
<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Is
there a way of simplifying the artificial lighting of the tenants
either side of the mall space? The goal of the artificial lighting in
the tenancies is not to be highly accurate but rather to give the
daylight in the mall space some context and to make it look more
realistic as I’m only concerned about the daylight in the mall. Ideally
I would like to put a mkillum surface in the position of the array of
lights but I feel that this wouldn’t help reduce the complexity of the
simulation as the same number of calculations still need to be carried
out, am I right?<br>
</blockquote>
<br>
</div>
The electric lights probably aren't doing much in terms of contribution
to the overall lighting that is predominantly from the skylight. In
this case you can use the glow material for your lights (with a small
radius, see the docs) to affect a visual context as you are looking for
without exacting a huge penalty on the render time.
<div class="im"><br>
<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"><br>
Is there a way in Radiance to make a planer object emit a certain
amount of uniform light?<br>
<br>
</blockquote>
<br>
</div>
Yep, the glow is the material you want for this. I have used it
infrequently but I believe this is exactly what you need to get these
renderings looking good and completing in reasonable timeframes.
<div>
<div class="h5"><br>
<br>
- Rob Guglielmetti<br>
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</div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Paul Chilton<br>
<br>
Renewable Energy Engineer<br>
<br>
[m] 0400 306 791 | [e] <a moz-do-not-send="true"
href="mailto:p.chilton@gmail.com">p.chilton@gmail.com</a><br>
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</blockquote>
<br>
<pre class="moz-signature" cols="72">--
# Jack de Valpine
# president
#
# visarc incorporated
# <a class="moz-txt-link-freetext" href="http://www.visarc.com">http://www.visarc.com</a>
#
# channeling technology for superior design and construction
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