IES Files in Revit 2011

[mthurnauer]

I have downloaded the Litecontrol Ciros light fixture from Autodesk Seek. My first challenge was that they made a nice type catalog to go with the family, but the type catalog has different referenced ies file names in it than the IES files that were posted with the family. Nice work!

My first question is, does it matter? Once the ies file has been loaded into the lighting family, is it still necessary for the family to be able to locate the IES file? Does the IES file need to be copied to C/program data/Autodesk/revit2011/IES? Can I keep the IES files in separate folders per manufacturer?

My next issue is that the light cutoff is very sharp and not what I would have expected from a custom light. The attached image shows two different light fixtures from Litecontrol. The one on the left shows the problem more clearly. You can see that the falloff is very strong. It could be that the geometry in the light fixture family is creating shadows. This would defeat the purpose of the IES file.

[KayMan]

I used to work for a lighting designer afew years ago where we used Max and Maya to visualise scenes using IES files.
The main issue with IES files is that the distribution of light is inaccurate with 1m from the actual light soruce........Also its difficult to get a consistant throw of light from a linear/area source from an IES.
Fianlly be carefull it you are using an IES with a fitting that has a different filture/diffuser thann whats stated within the IES file (you can open them up in textpad to view all the details)

As for where they are stored....I beleive that they can be stored anywhere

[mthurnauer]

I have read through the directions from IES about creating fixtures using ies files. I have a theory about the problem. When I have used custom lights in other programs, the light distribution may be defined on multiple planes giving it a 3d distribution model. Even for a linear fixture, the source would be defined as a point and then the rest of the distribution would be based on the ies profiles. In the linear fixtures, it is as if the profile is used only as a cross section through a linear source. This ends up making the falloff at the end of the fixture unrealistic and it multiplies the distribution along the path of the linear source. I tried changing the source of the light from linear to point and what I ended up with looked like the attached image. You will see that it illuminates a one foot long section and then it falls off immediately. I am really surprised that custom lights worked great in Lightscape over ten years ago and now they are pretty useless.

[SamuelAB]

The problem is that the light source is inside the geometry that casts shadows to the light source.

The solution to see the real light distribution is to hide the fixture geometry, I have a parameter that does this, I call it rendering. This is not a real solution.

The real solution is that within 3ds Max, you can have geometry not cast shadows, they need to implement something similar to Revit. This way the geometry of the light will not affect the light being cast.