What info is actually in an ies file?

[alias_marks]

Hi there, we're playing around with the new lighting tools in 3ds max design 2009 for lighting studies. i.e. how many ft. candles are we getting along a given path using a given fixture etc. Or what is the given light hitting this interior work surface during the solstice. etc.

 

From what I understand, the ies file gives you a spread in how the light will cast on surfaces, but does it carry the intensity of the light with it? Or the shadows that are being cast from the fixutre itself? (like a bollard) When we load an ies file, it automatically changes the cd intensity, but then it's easy to slide this value up and down (not locked in). what info comes with the ies file, and what information is up to us to plug in?

 

Also, we're wondering how to set up glazing materials accurately. It seems to me that you wold want to plug in more information into the glass material than just the 0%-100% transparency to be accurate. Any insight here?

 

Thanks much,

 

DownTown MikeBrown

[Koper]

for glazing, i would look at the IOR values and not the transparency value, as anything that lets light through will distort it, even hot air.

 

a quick google search gave these two sites

 

http://www.m3corp.com/a/tutorials/refraction.htm

&

http://blenderartists.org/forum/archive/index.php/t-71202.html

 

for IES, i thought its just data of getting the real physical shape of the distribution of light, not the intensity or color. Max just allows you to simulate the intensity and color. If you're looking to simulate a real light source, you'll have to input their Kelvin and intensity values, and use the ies data of that light as the physical distribution

 

anothe site for IES info

http://www.cgarena.com/freestuff/tutorials/max/ieslights/

 

Is it possible to post some of your findings here? it would be interesting.

 

A

[Devin Johnston]

I've found that unless your scene is set up properly you won't get the benefit IES lights offer, which usually translates into adjusting the power of the light so that it shows up in your scene. Once you've done that you've basically thrown away any chance you had at creating a "physically correct" lighting setup.

 

It sounds like you are trying to set up your lighting and materials in a physically correct manor; in that case you'll have more luck with programs like Maxwell or Fry. 3D Studio isn't really set up for physical correctness and that's obvious when your trying to create more accurate materials like glass.

[shaneis]

Michael,

 

go to this page http://www.erco.com/guide_v2/guide_2/simulation_95/simulation_95/en/en_simulation_prog_1.htm

 

The links on that page should have all the information you need. I also strongly recommend scouring the entire Erco site - in my opinion, it's the best source of lighting information on the web...hands down!

 

EDIT: You should also look into the i-Drop software from Autodesk...

http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=1862830

Edited October 28, 2008 by shaneis

[alias_marks]

great, thanks so much for the info. You are correct. we are trying to be as accurate as possible. Attached is an image we've created so far, but we're trying to back the validity of it. We're just dropping in ies files. We're not so much going for the actual visual representation that fry or maxwell might provide. The ft. candle reading are what's important to us here.

 

For example, we have dozens of bollards along this walkway path, but how does the transparency of the bollard glass that the bulb inside? Know what I mean?

 

I appreciate the IOR suggestion. That's helpful for other materials. We're mostly looking at varying glass conditions though which mostly have a 1.6 IOR. What if the glass was tinted or has a light transmittance value of 45% say? How do we translate that to an actual mental ray pro material?

 

Thanks for the responses.

[alias_marks]

ps, yes, we have been watching 'predator' as a case study to see how creatures from other planets have been able to do these kind of studies with their evolved vision systems.

[shaneis]

...but how does the transparency of the bollard glass that the bulb inside? Know what I mean?...

 

Ah, now I see what you mean. Each IES profile should contain that data. So an IES profile for X lamp in Y light fitting will produce Z IES profile for the complete luminaire.

 

An example can be seen on the Erco site. If you download the zip folder for the "Grasshopper" luminaire's, you will find 11 different IES profiles in the zip folder, each representing a variation on the entire luminaire (different lamps, lenses, diffusers and housing sizes). Four of them are for the "HIT-TC-CE-35W" lamps but all are slightly different in their numbering. The reason being each represents a slightly different luminaire.

 

For example, if you look at the following link, you'll see a good diagramatic explanation of this comparing two pendant luminaire's with the same lamps and the same 12" reflectors although one has a glass diffuser, the other doesn't.

 

http://www.arch.virginia.edu/arch541/Handouts/render/lamps.html

 

Troubles with IES profiles will arise if the manufacturer doesn't provide a good up-to-date profile or if your clients change the lamps or parts of the fittings (eg. lenses/ diffusers). Ideally, they should use luminaire's that have not been altered, i.e. are they using the original lenses and lamps.

 

[shaneis]

...We're mostly looking at varying glass conditions though which mostly have a 1.6 IOR. What if the glass was tinted or has a light transmittance value of 45% say? How do we translate that to an actual mental ray pro material?

 

The more common glass in use for normal glazing is "float glass" and has an IoR of 1.52 and glass used for jars, bottles and containers is typically the same type of glass as float glass - "soda-lime glass" but it has a lower IoR of 1.518 due to the effects that manufacturing has on the material. Laminated float glass effectively has the same IoR as non-laminated float, it won't be exactly the same, but as the IoR of the PVB laminate would vary, it's safe to assume it is consistent with the glass's IoR. Laminated glass is always 0.38mm (0.014") thicker except for heavily patterned glass and automotive laminated glass which often has a thicker laminate at 0.76mm (0.030") and some manufacturers use combinations of float glass and toughened/ tempered glass. Some special use laminates are 0.8mm (0.031") or 1.6mm (0.062") thick. Toughened/ tempered glass has the same IoR as float glass.

 

As for translating tints/ translucence values into mrMaterials, you could source the relevant data from material specification sheets and apply those figures to the relevant attributes of the mrMaterial. Glass should always have Fresnel reflection.

 

As each country has it's own glazing standards so to get the most accurate data, you'd need to download the full product brochure from a major manufacturer like Pilkington... for the US, it's

 

http://www.pilkington.com/the+americas/usa/english/default.htm

[alias_marks]

Shane! Great info, I feel enlightened Thanks for taking the time to explain thoroughly.

 

M-