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nldrucker
Posts: 5
Registered: ‎05-27-2010
Message 1 of 9 (1,935 Views)

Problem rendering when using an "Absolute" IES Photometric file as a data source

1935 Views, 8 Replies
08-10-2011 10:47 AM
Has anyone had a problem rendering when using "absolute" IES photometric files. These files describe the performance of LED source based lighting fixtures, both exterior and interior. I have a work-around ( I think) but I wanted to see if anyone else is have this problem and what fixes, if any might have been used.
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ccollins
Posts: 866
Registered: ‎09-28-2009
Message 2 of 9 (1,934 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

08-10-2011 10:51 AM in reply to: nldrucker

Edit the family, and under light source, change it to one of the "non-photometric" types.

The .ies file is probably causing some issues when rendering with mental ray.

 

cheers

Cliff B. Collins
Registered Architect/BIM Manager
Thalden Boyd Emery Architects
St. Louis, MO
Member
nldrucker
Posts: 5
Registered: ‎05-27-2010
Message 3 of 9 (1,932 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

08-10-2011 11:06 AM in reply to: ccollins
Thanks and yes that is one work-around but you are not representing the fixtures performance correctly in the rendering. As a lighting designer that is a NO-NO. What I did was correct the data file to remove the "absolute" designator a "-1" (the second data item after the files description lines) with the measured lamp (light source or LED module) lumen value, you must also account for the number of lamps (or light sources) in the fixtures. If you understand the IES photometric file format and what they represent it's easy - if not this is not for the faint-of-heart and you can very easily corrupt the file. Sorry people are having this problem but nice to know I'm not alone - do you think Autodesk aware of the issue?
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ccollins
Posts: 866
Registered: ‎09-28-2009
Message 4 of 9 (1,928 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

08-10-2011 11:17 AM in reply to: nldrucker

I'm not sure that the high level of detail you are after is actually possible using Mental Ray inside of Revit.

 

Perhaps in 3dsMax Design this is possible--so I'm not sure all the extra effort in Revit is worth it.

 

Have you seen this: ???

 

http://www.elumtools.com/index.php?id=64

 

This might be a good compromise for getting accurate lighting studies inside of Revit.

 

And, yes--I understand photometrics and .ies files.

 

cheers

Cliff B. Collins
Registered Architect/BIM Manager
Thalden Boyd Emery Architects
St. Louis, MO
Member
nldrucker
Posts: 5
Registered: ‎05-27-2010
Message 5 of 9 (1,922 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

08-10-2011 11:37 AM in reply to: ccollins
Cliff: So you can appreciate my frustration - when I adjust the file, Revit renders just fine, the idea is to give the user one environment to be working in during SD or DD. You're correct if you need a great rendering then 3dsMAx is the way, as long as you don't distort the result to get the pretty picture. For "lighting" accurate studies AGI32 is still the best tool (in common use) an offers advantages to ray tracing, not to discount the important of ray tracing. I'm a Beta test site for elumtools and have worked with Lighting Analysts for a very long time, back to the earliest version of AGI32. Elumtools is going to be a great tool and addition to Revit but it is in it's infancy - looking forward to a mature product soon. This all started as I began to develop Revit Families for my exterior luminaries RAB Lighting - we are establishing our presents in the BIM world so my adventure is just beginning, we'll be on Autodesk Seek and CADdetails soon - looks like it will be a fun ride. Thanks for your comments - NLD
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ccollins
Posts: 866
Registered: ‎09-28-2009
Message 6 of 9 (1,920 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

08-10-2011 11:42 AM in reply to: nldrucker

Glad to hear it. We need more good content for Revit.

Let us know when you have some products up on Seek or a website.

 

If we like them, they just might get spec'd on one of our projects!

 

cheers

 

Cliff B. Collins
Registered Architect/BIM Manager
Thalden Boyd Emery Architects
St. Louis, MO
Distinguished Contributor
thewrz
Posts: 171
Registered: ‎06-08-2009
Message 7 of 9 (1,760 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

12-31-2011 04:25 PM in reply to: ccollins

Thought I'd bump this thread to illuminate (heh, pun intended) some of the issues Revit has with absolute IES files.

 

The work around is to change the "initial lumens" value in the IES file from "-1" (meaning it's absolute) to the lumen value of the fixture.

 

In my example. I was using the Lithonia 2RTL2 LED light fixture and an absolute IES file (sounds like a terrible vodka) from Lithonia's website. Attached.

 

I also compared it to the standard version of this fixture, the 2RT5 with  two, 14 watt, T5 fixtures at 3500 Kelvin. Also attached.

 

Here's the first go:

front view.jpg

 

As you can see. The "absolute" IES file gave us our lovely rainbow we're used to seeing when rendering with absolute IES files in Revit. On the right is the traditional fluorescent IES file with it's initial lumen value set at 2400 (2 x 1200).

 

Then I read this little article to get a better understanding of the IES file format:

http://www.vuw.ac.nz/architecture-onlineteaching/tutorials/lightscape/extras/ies_standard_format.htm...

 

As you can see it explains where the "-1" goes in the IES file. Find it, and you'll be halfway there. So I changed the "-1" to the initial lumen value of the LED fixture of "3300" as stated in the IES file. I added "_AW" to the end of the file for my modified version. Attached.

 

Here are the results:

front view fixed.jpg

From left to right: Original LED ies file, modified LED ies file, and original fluorescent IES file.

 

FROM WHAT I HAVE OBSERVED. The light web appears to have remained intact allowing Revit to render. It will probably not be as accurate since I have monkied with something I do not fully understand (the IES file format).

 

However it appears this work-around succeeded. 

 

AS OTHERS HAVE MENTIONED, I DO NOT USE REVIT AS A LIGHTING ANALYSIS TOOL! I only use it for rendering out images to put in promotional material or meetings with clients.

 

Currently, we use ElumTools and LightPro in our office to do accurate point-calcs. The former, ElumTools, being a brand new extension that uses the Revit API to link in AGI32s lighting calculation system for accurate point calcs. ElumTools does understand the absolute value and will produce accurately thrown light.

 

As always, with all work-arounds, YMMV. Finally, here is the light fixture family:

http://dl.dropbox.com/u/22838635/Recessed%20-%20Volumetric%20-%20Lithonia%20-%20RT5.rfa

 

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New Member
alkassim
Posts: 1
Registered: ‎06-28-2012
Message 8 of 9 (1,517 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

06-28-2012 03:27 AM in reply to: nldrucker

Re: Problem rendering when using an "Absolute" IES Photometric file as

Distinguished Contributor
thewrz
Posts: 171
Registered: ‎06-08-2009
Message 9 of 9 (1,502 Views)

Re: Problem rendering when using an "Absolute" IES Photometric file as

06-28-2012 08:50 AM in reply to: alkassim

Just an update to this topic.

 

I've taked with Autodesk support.

 

This is a known issue that both the Revit and 3ds Max team are working on.

 

Both use the "Mental Ray" rendering engine. With Revit you have no choice but to use it, but in 3ds Max you can use "scanline" or w/e it's called. So if you want to render scenes with absolute IES files in 3ds Max -- use the 3ds Max engine.

 

But it's really all on the Mental Ray team's shoulders. It's their engine which doesn't like absolute IES files so we'll have to wait to hear from them. (I've emailed the Mental Ray team directly, but they haven't responded yet).

 

 

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