CIE standard overcast sky sim

Glen - UK · March 11th, 2005

I'm a newby to Lightscape and I'm currently trying to simulate a standard CIE overcast sky for a UK building project. What I am a little unsure about is within Lightscape and under 'Daylight' it is possible to either set the slider as 'cloudy', without 'direct control' ticked, in which case the program appears to assume a cloudy 16,000 Lx sky or if you tick direct control you can adjust the sun illuminance to match your required level - which in the UK would be 5000Lx for 85% exceedance. My concern is if I tick Direct Control, do I actually have a dim sun in an un-uniform sky ie a brighter spot in the sky where the sun is or if I still have the previous slider set to cloudy but sun illuminance set to 5000Lx does it actually simulate a true standard CIE overcast sky at 5000Lx?
With direct support from Lightscape now being withdrawn this forum is my only hope of progress.
Thanks
Glen

Jaguar lover · March 11th, 2005

Hi there Glen!

This will not be the answer to your qustion but expanding the possibilities in simulation. (if you didn´t know it before that is!)
You might want to check out:
Ecotect for building sim. -includes a front end for Radiance

http://www.squ1.com/site.html

I use Lights Studio from Lichtplaner -front end for Radiance- Its a plugin for max.
http://www.lichtplaner.com/

from radiance you get Daylight factors etc.

cheers
/Kent

Glen - UK · March 11th, 2005

Kent,
Interesting, but we are now rather committed to using our Lightscape model so I cannot do a U turn at this stage.
Thanks anyway.
Glen

Arnold Gallardo · March 24th, 2005

Ok AFAIK, LVS uses the CIELAB skydome algorithms or at least conforms to it. This information is based on an old question I asked the Lightscape principals. Of course I was not able to acquire more detailed information because this question borders on proprietary information but the skydome does get substructuring and meshing based on my tests. Sorry this is only the information that I have.

Ernest Burden · March 24th, 2005

Quote:

Originally Posted by Arnold Gallardo

the skydome does get substructuring and meshing based on my tests. Sorry this is only the information that I have.

Implemented how?

Arnold Gallardo · March 24th, 2005

Hi Ernest,

I don't exactly know how. You will need to ask Filippo (Tampieri) or Rod (Recker) to know that. In the early days I have been asking a lot of technical questions and could not really get detailed anwers because they were proprietary information. I had to do my own tests to evaluate LVS's capabilities on my own and demonstrate my situation and problems to Lightscape principals when I encounter an issue.

del82 · March 25th, 2005

Arnold, whens your book on Lightscape coming out? I bet it would be a Top Seller in a week

Arnold Gallardo · March 26th, 2005

Funny

A bunch of use was going to do this actually before Lightscape's support got pulled off. We were actually down to making an outline and delegating which topic is going to be covered by whom but after Lightscape was dropped the project died.

Now if it was a VIZ/Lightscape or generic arch-vis book that would fly.

del82 · March 28th, 2005

Viz and Ls, hmm not bad idea at all. Maybe also some modeling chapters and tips for Ls...then how to combine/transfer Ls. file to Viz/Max for better surface materials...combinig the two softwares...
It could realy be a Hell of a Book!!!!...not to mention again it would be a top seller

Richard McCarthy · March 29th, 2005

I think if you are concerned with Lightscape's accuracy in daylight simulation, there is a good article in cgarchitect's resource that talk about that topic :

http://www.cgarchitect.com/resources...Lightscape.pdf

http://www.sbse.org/awards/docs/Shalaby.pdf

March 11th, 2005	#1 (permalink)
Glen - UK Junior Member Join Date: Mar 2005 Location: UK Age: 46 Posts: 2 Name: Glen Irwin	CIE standard overcast sky sim I'm a newby to Lightscape and I'm currently trying to simulate a standard CIE overcast sky for a UK building project. What I am a little unsure about is within Lightscape and under 'Daylight' it is possible to either set the slider as 'cloudy', without 'direct control' ticked, in which case the program appears to assume a cloudy 16,000 Lx sky or if you tick direct control you can adjust the sun illuminance to match your required level - which in the UK would be 5000Lx for 85% exceedance. My concern is if I tick Direct Control, do I actually have a dim sun in an un-uniform sky ie a brighter spot in the sky where the sun is or if I still have the previous slider set to cloudy but sun illuminance set to 5000Lx does it actually simulate a true standard CIE overcast sky at 5000Lx? With direct support from Lightscape now being withdrawn this forum is my only hope of progress. Thanks Glen

March 11th, 2005	#2 (permalink)
Jaguar lover Member Join Date: Aug 2003 Location: Sweden Posts: 60 Name: Kent Hulusjö	Re: CIE standard overcast sky sim Hi there Glen! This will not be the answer to your qustion but expanding the possibilities in simulation. (if you didn´t know it before that is!) You might want to check out: Ecotect for building sim. -includes a front end for Radiance http://www.squ1.com/site.html I use Lights Studio from Lichtplaner -front end for Radiance- Its a plugin for max. http://www.lichtplaner.com/ from radiance you get Daylight factors etc. cheers /Kent __________________ Never quit learning!

March 11th, 2005	#3 (permalink)
Glen - UK Junior Member Join Date: Mar 2005 Location: UK Age: 46 Posts: 2 Name: Glen Irwin	Re: CIE standard overcast sky sim Kent, Interesting, but we are now rather committed to using our Lightscape model so I cannot do a U turn at this stage. Thanks anyway. Glen

March 24th, 2005	#4 (permalink)
Arnold Gallardo Senior Member Join Date: May 2002 Location: New York Posts: 225 Name: Arnold Gallardo	Re: CIE standard overcast sky sim Ok AFAIK, LVS uses the CIELAB skydome algorithms or at least conforms to it. This information is based on an old question I asked the Lightscape principals. Of course I was not able to acquire more detailed information because this question borders on proprietary information but the skydome does get substructuring and meshing based on my tests. Sorry this is only the information that I have. __________________ _ _ ______________ _ _ Arnold Gallardo Visual Content Creator Technical Writer Author:'3D Lighting: History,Concepts and Techniques'

March 24th, 2005	#6 (permalink)
Arnold Gallardo Senior Member Join Date: May 2002 Location: New York Posts: 225 Name: Arnold Gallardo	Re: CIE standard overcast sky sim Hi Ernest, I don't exactly know how. You will need to ask Filippo (Tampieri) or Rod (Recker) to know that. In the early days I have been asking a lot of technical questions and could not really get detailed anwers because they were proprietary information. I had to do my own tests to evaluate LVS's capabilities on my own and demonstrate my situation and problems to Lightscape principals when I encounter an issue. __________________ _ _ ______________ _ _ Arnold Gallardo Visual Content Creator Technical Writer Author:'3D Lighting: History,Concepts and Techniques'

March 25th, 2005	#7 (permalink)
del82 Veteran Member Join Date: Oct 2004 Location: Croatia Age: 74 Posts: 512 Name: Mario Pende	Re: CIE standard overcast sky sim Arnold, whens your book on Lightscape coming out? I bet it would be a Top Seller in a week __________________ Beeeee!

March 26th, 2005	#8 (permalink)
Arnold Gallardo Senior Member Join Date: May 2002 Location: New York Posts: 225 Name: Arnold Gallardo	Re: CIE standard overcast sky sim Funny A bunch of use was going to do this actually before Lightscape's support got pulled off. We were actually down to making an outline and delegating which topic is going to be covered by whom but after Lightscape was dropped the project died. Now if it was a VIZ/Lightscape or generic arch-vis book that would fly. __________________ _ _ ______________ _ _ Arnold Gallardo Visual Content Creator Technical Writer Author:'3D Lighting: History,Concepts and Techniques'

March 28th, 2005	#9 (permalink)
del82 Veteran Member Join Date: Oct 2004 Location: Croatia Age: 74 Posts: 512 Name: Mario Pende	Re: CIE standard overcast sky sim Viz and Ls, hmm not bad idea at all. Maybe also some modeling chapters and tips for Ls...then how to combine/transfer Ls. file to Viz/Max for better surface materials...combinig the two softwares... It could realy be a Hell of a Book!!!!...not to mention again it would be a top seller __________________ Beeeee!

March 29th, 2005	#10 (permalink)
Richard McCarthy Veteran Member Join Date: Apr 2003 Location: Australia Posts: 757 Name: Richard McCarthy	Re: CIE standard overcast sky sim I think if you are concerned with Lightscape's accuracy in daylight simulation, there is a good article in cgarchitect's resource that talk about that topic : http://www.cgarchitect.com/resources...Lightscape.pdf http://www.sbse.org/awards/docs/Shalaby.pdf __________________ Don't mess with my hat !!

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