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

12 REPLIES 12
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Message 1 of 13
nldrucker
5290 Views, 12 Replies

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

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.
12 REPLIES 12
Message 2 of 13
ccollins
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
Message 3 of 13
nldrucker
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?
Message 4 of 13
ccollins
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
Message 5 of 13
nldrucker
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
Message 6 of 13
ccollins
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
Message 7 of 13
adam.jw
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

 

____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 8 of 13
alkassim
in reply to: nldrucker

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

Message 9 of 13
adam.jw
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).

 

 

____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 10 of 13
ABRAHAMCHANDLER
in reply to: nldrucker

I can confirm this workaround. - Using Revit 2014, modified the ies file in notepad as such (see screenshot). The hightlighted text used to read "-1", now replaced with the lumen output of that fixture. 

 

Sample

 

 

Sample2

Message 11 of 13

hi, can i know where can i find the notepad area to edit?

 

Message 12 of 13
adam.jw
in reply to: peiyin0112

The previous posts in this thread explain how to do this. Please re-read them.
____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 13 of 13

To know the lumen output of the IES file, you can process the IES file here and look at the cumulative lumen value.

 

https://www.visual-3d.com/tools/photometricviewer/

 

Replace the -1 with the resulting value. Also, enter this lumen value in your Revit family parameters, Revit will not do so automatically.

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