How to properly simulate RGB LEDs ?

[Headroom]

Ive been using Indigo for several years now to develop my RGB LED lighting systems and recently installed one that uses LEDs with a slightly different color of blue as posted in this thread http://www.indigorenderer.com/forum/vie ... =4&t=13552

So far my renders have very closely approximated these LEDs and the renders looked very close to the actually build system. As can be seen when comparing the rendered image with an actual photograph of the installed system following the link to the above mentioned thread the color in the installed system is much more blueish and provides super saturated reds and purples.

The reason for this is that so far I'd been using the "normal" blue LEDs but this time instead of blue I used the royal blue LED.

Normal blue LED
70lm @ 700ma
Typical Wavelength 470 nm
Wavelength Range 460 to 485 nm

Royal Blue LED
1030 mW @ 700mA
Typical Wavelength 447.5 nm
Wavelength Range 440 to 460 nm

Here's a link to the detailed spec sheet for the color LEDs http://www.luxeonstar.com/assets/downloads/DS68.pdf

My questions is how would I define these LEDs ( and LEDs in general) properly in Indigo to better approximate the color of these LEDs ?

[Zom-B]

If you have the Wavelength Data for your LED, you could use it to feed Indigo!
Here an example material, check out the "view source" button on the top:
http://www.indigorenderer.com/materials/materials/272

[Headroom]

Well, that's exactly the problem. I don't have that sort of data and I am somewhat doubtful it's available from the manufacturer. I'll give that a try, however.

In the meantime the only "data" I have available is the linked spec sheet, which leaves me with two options:

1. I somehow approximate the tabulated spectra data (I am assuming that's wht Indigo uses in the LED material you linked to) based on the numbers and graphs/charts in that spec sheet. But I have to admit thats exceeds my currnet abilities.

2. I measure the spectral distribution of these LEDs myself. While that would be a very interesting learning experience I dont have a spectrophotometer and these things are not cheap.

Perhaps there are other ways to retrieve that sort of data ?

[Zom-B]

If I'm not totally wrong, the data from page 11 can be transcribed to such tabulated Data by hand

[Headroom]

Some more detailed hints would be very helpful.
I followed the link to the material posted by galinette (Etienne). Unfortunately I cannot find any information what technical unit these numbers represent.

Also, the charts in the spec sheet are normalized to 1 so have to be multiplied by "something" to arrive at a technical value. Also "real" measured spectra usually are not as smooth as the curves shown in the spec sheet. If one charts the data for the blue LED material in the DB liked to earlier in the thread it looks different then the curve for the blue LED in the chart in the spec sheet.

[CTZn]

Also, the charts in the spec sheet are normalized to 1 so have to be multiplied by "something" to arrive at a technical value.

You can use normalized data alright, the amplitude is given by the "Product Selection & Optical Characteristics" chart, "Typical Luminous Flux (lm) or Radiometric Power (mW)" column.

I think I would use data extrapolated from Table 3 and Figure 5 in order to reconstruct tabulated data.

[Headroom]

Thanks for the help so far!

Yes, that was my thinking was well but in order to do that I still need to know what the tabbed values for example in the blue LED material represent. That question remains unanswered.

I feel thats a very straight forward question about I cannot find that in any form of documentation. What happened to the Indigo Technical Reference ?

Can the tabulated values be edited in the Indigo UI or does one create these form of light sources/materials with a plain text editor ?

The "Tabulated" window in the Indigo UI material editor is not accepting any input.

[fused]

Thanks for the help so far!

Yes, that was my thinking was well but in order to do that I still need to know what the tabbed values for example in the blue LED material represent. That question remains unanswered.

I feel thats a very straight forward question about I cannot find that in any form of documentation. What happened to the Indigo Technical Reference ?

You can find it in the Indigo install directory.

Can the tabulated values be edited in the Indigo UI or does one create these form of light sources/materials with a plain text editor ?

The "Tabulated" window in the Indigo UI material editor is not accepting any input.

Not yet, unfrotunately

[thesquirell]

But, but! Coming soon!

[Headroom]

Again, thanks for the feedback. I have no problems editing materials using a text editor andf have done that many times in the early Indigo days.

The main qustion, however, is still not answered.

What physical unit do the tabulated values represent ? Pretty please, wich cream on top

I have an older (2009 for Indigo V2) Technical Reference and it makes no mention of the physical units.

@thesquirrel
Howm did you creat this screenshot. We I selec the "Tabulated" tab with te blue LED material loaded the window is blank and I cannot see a curve.

[thesquirell]

It is a new feature coming up with the new Indigo 4. To quote super awesome user fused, it will be available for "every wavelength dependent channel"!

[fused]

The main qustion, however, is still not answered.

What physical unit do the tabulated values represent ? Pretty please, wich cream on top

Sorry, should have answered that before.

I'd say it's unitless, as the document said they were normalised, somewhere. (or maybe I read that from the graph)

You could use Indigo's emission scaling to get the power you want, or scale the data by hand.

I have an older (2009 for Indigo V2) Technical Reference and it makes no mention of the physical units.

You'd really have to ask someone else about the underlying pysical stuff

[Headroom]

Well...I was hoping that one of the devs could chime in but...


In the meantime I've tried to apply what you've suggested just using the blue LED material.

Loading it into Indigo directly, I don't see how I can "scale" this data using the emission scale in the Indigo UI.
When I apply this material in Blender it is an externel material and I am also not providedd with a "scaling" method.
Also, I've applied the blue LED material (as shown in the screenshot) to the blue sphere and tried to export and render it and Blender/Blendigo report wit an eror and nothing is being exported ('nother screenshot)

The Technical Reference alos is not overly explanatory and was last updated in May 2013.

Son, in essence, I am still stuck :/

[Oscar J]

That last error message shows up when you have materials, textures or objects with non-ascii characters in their name or directory, such as å, ä, ö, ü and others. Check your names and directories for weird characters.

[Headroom]

That last error message shows up when you have materials, textures or objects with non-ascii characters in their name or directory, such as å, ä, ö, ü and others. Check your names and directories for weird characters.

Thanks for the help!
I should have checked this earlier as the giveaway is right in the error message.
There is a "strange" charter in the material file (not the file name).

Now Blender exports fine and renders but of course I still need an answer from that "someone else" as to what the physical unit is.