Illum rules of thumb

Hi group.

What are good rules of thumb regarding illum creations? It seems
triangular illums are not good for some reason. Long polygons are not
good. (How do you define long? Aspect ratio not to exceed?) Large
polygons are not good. (How "large" is too large?)

I'm looking at studying a building with a lot of odd exterior glazing
where I will need to be very creative making my illums. In this case I
think I will be forced to create my illums outside the building... which
I don't think is ideal since it avoids some issues only to create
others...

Well thanks for any information.

Mark

I'm looking at studying a building with a lot of odd exterior glazing where I will need to be very creative making my illums. In this case I think I will be forced to create my illums outside the building... which I don't think is ideal since it avoids some issues only to create others...

Why do you want to create the illums outside?

CU Lars.

···

--
Lars O. Grobe
[email protected]

Lars,

I wish I could attach images, as perhaps there is another way to do
this. But the reason for the exterior illums is that the interior
architecture follows the windows, forcing me to use triangular illums at
some point if I am to seal each opening. (window panes are not
rectangular either) Or each opening can be sealed from the outside.

Mark

···

------------------------------

Message: 2
Date: Thu, 29 Jul 2004 19:28:25 +0300
From: Lars O. Grobe <[email protected]>
Subject: Re: [Radiance-general] Illum rules of thumb
To: Radiance general discussion <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I'm looking at studying a building with a lot of odd exterior glazing

where I will need to be very creative making my illums. In this case

I think I will be forced to create my illums outside the building...

which I don't think is ideal since it avoids some issues only to
create others...

Why do you want to create the illums outside?

CU Lars.
--
Lars O. Grobe
[email protected]

------------------------------

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Mark de la Fuente wrote:

Lars,
I wish I could attach images, as perhaps there is another way to do this. But the reason for the exterior illums is that the interior architecture follows the windows, forcing me to use triangular illums at some point if I am to seal each opening. (window panes are not rectangular either) Or each opening can be sealed from the outside.

Hi Mark,

Yeah, triangular polygons are not a good fit with mkillum, because of the way source sampling works. The triangular polygons are usually the source of the "aiming failure" errors seen when running mkillum. The best explanation is of course in the Rendering with Radiance text. Do you have a copy? If so, this problem is addressed on pg 577.

Your building seems a challenge for mkillum. Are you trying to create pretty pictures, or get some illuminance data at points? If the former, it may still be worth the effort to try and seal your opening -- from the inside -- with a combination of polygons less likely to generate failures. If the latter, it's probably best to simply crank up the ambient calculation parameters, and wait it out. (This method could also be used for pretty picture generation, but now you're talking about *really* waiting...

···

----

      Rob Guglielmetti

e. [email protected]
w. www.rumblestrip.org

Georg, Thanks for the detailed response! You bring up a good point.
Since in this case the outside geometry is a downtown area, and the
shading from all the buildings will have a great effect on the study,
the illums will have to be subdivided to a reasonable degree in order to
properly account for all the shadowing.

Actually your response brings up another question! :slight_smile:

If one were to have a complex daylight entry system at the windows,
wouldn't it make sense to run a mkillum calculation with illums outside
first, and then a second mkillum calculation (with the first set of
illum planes in the octree) of illum planes inside (beyond the daylight
entry system)? You could get carried away with this, but hopefully you
get what I'm getting at.

Mark