[Eric Lagman]

Doh this was such a great thread and now all the images dont show up. Does anyone have the mxs of the led modeling method that turned out the best. Im trying to model the led properly, but can only see the screencaptures from dd's post. Any help would be greatly appreciated.

[Tea_Bag]

Unlucky bout this thread! - I'm working on LED's for CGSphere! Very tricky working with LED's I might have to improvise

Great work and test from the guys in this forum!

[mtripoli]

Some leds I did awhile back...

[def4d]

wow

[-Adrian]

Looking good!

[mtripoli]

I don't want to overstate this but JDHill (thanks JD!) cleared this up for me a long time ago.

Regardless of the shape of the led the most important thing is that the emitter must be in a sphere (or any other shape you want). It must be isolated from the plastic outside. The shape of the resulting pattern is defined by the "lens" of the led. The led depicted is a standard "1-3/4". There are many different designs that give different output "shapes". The other thing to remember is the shape of the cone that the emitter sits in . This is important to the projected pattern as well. If you want to go to the extreme put a small circular dot in the middle of the led chip. Real leds have a center spot that does not light;it's the bonding wire spot.
Hope this helps:

[dd_]

this is my take on the LED

[Cadhorn]

To further complicate things, I have two small bits of possibly critical info about LEDs, gleaned from a product demo/slideshow given by some dudes from ColorKinetics. (I'll try to get copies of the relevant slides and post them here later.)

1. The light that's emitted by the diodes is mostly (~95%?) emitted straight out from the surface of the LED. Maybe that was obvious to everyone else, but I'd been assuming that it was more omnidirectional, and that the "focusing" of the light was a product of the reflectors around the diode itself.

2. There is a very thin and even layer of clear (or possibly slightly tinted) material deposited directly onto the diodes.

2a. (?) The technology of producing LEDs is evolving *rapidly*. If you're using reference photos/information from two-five years ago, it's a good possibility that you're modeling old stuff.

2b. It's a huge pain in the ass to recreate these suckers... I truly wish we had some shortcut (via an .ies type description of light produced) but I'm not holding my breath as this is clearly not the Maxwell Way. (let's just hope that we get a 1000x speed boost in renderings via some CUDA type tech soon!)

[mtripoli]

I'd take what they said in relation to their product; not leds in general.

1.)The "shape" of light emittted from an led is a function of the "cup" (many manufactuers claim all different things about the shape of the cup and how it contributes to the light output. It's more hype than anything else. When designing product with leds this has never come up). The light "shape" is a function of the led lens. You have to look at the spatial distribution shown in the data sheet for the part you plan on using. An led can have 10, 12, 14, 16 ~ 100 degrees of spatial distribution. I've posted a few data sheets that you can have a look at to see what I'm talking about.

2.) Again, you have to look at the data sheet. A "white" led is in fact a blue led with a white phosphor coating. The blue led excites the phosphor making it look white. There a many different "shades" of phosphor so you can get white leds that have a tint of yellow, blue. This used to be a huge problem with white leds; they had to be binned for color before shipping, otherwise you could get a yellow tint next to a blue tint. I think they've improved this so that it less of a problem.

2a.) I disagree. Although the materials may be changing the lens types are very standard. Efficiency has changed dramatically but not the fundamentals.

One thing that people overlook quite a bit when using leds is frankly, how easy it it to use one. Get a battery, resistor and led and there you go; a light. Again I'll refer to the data sheets; led brightnes is a function of how much current flowing through the thing. Don't mistake what I just said "current"; not applied voltage. Regardless of voltage the correct amount of current must flow or you'll get a "dark emitting diode" d.e.d). The spec sheet will tell you how much current to use to get the best efficiency and light output. Once you know that it's up to you. More current = brighter led = shortened life. An led has a maximum current for a specified time. In other words you can put 20mA through an led rated for continuous use, or you can put 2A through the led for 10mS. Given that if you want to make a really bright led pump 2A through it for not longer than 10mS. If you do this fast enough the eye doesn't see the flicker.

Wikipedia actually has a nice page on leds:
http://en.wikipedia.org/wiki/LED
Data sheets for a few leds:
http://www.hex7systems.com/maxwell/leds/10deg.pdf
http://www.hex7systems.com/maxwell/leds/12deg.pdf
http://www.hex7systems.com/maxwell/leds/16deg.pdf

[Maximus3D]

Found this one tonight when i were looking for other type of info.. maybe it's useful to you LED guys.

http://www.zemax.com/kb/articles/38/1/H ... Page1.html

Btw, this Zemax program looks pretty nice! check the main url zemax.com

/ Max