Indigo 1.1.10

General News and accouncements regarding the Indigo render engine
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suvakas
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Post by suvakas » Wed Sep 24, 2008 2:16 am

Gotcha !
But nothing tells me, that the next error message won't be - unexpected element 'blackbody' in element 'constant' :wink: (if you get what i mean).
But yeah, i admit it - i was too lazy to do trial and error myself. So thank you again for the correct syntax.

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CTZn
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Post by CTZn » Wed Sep 24, 2008 4:11 am

Remove everything it tells you to remove until it says it lacks something, and add that thing :evil: :wink: Either that will fix the problem, or report it to Ono (unhandled error).

Admitedly I'm very lazy too but I said so many stupid things that I had to check and report, you are welcome :)
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delle
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Re: Indigo 1.1.10

Post by delle » Tue Nov 04, 2008 1:04 am

OnoSendai wrote:
Whaat wrote:
OnoSendai wrote: The emission scaling functionality now is basically a superset of the old efficacy scale functionality.

The old way of setting the power drawn (Watts), and overall luminous efficacy (lm/W) was basically a convoluted way of specifying the luminous flux (lm) of the light, which is just the product of the power drawn, and the overall luminous efficacy.

With the new emission scale system, you can just set the luminous flux directly. In addition, you can also scale the emission of the light according to other measures, such as luminance, luminous intensity, and luminous emittance.

To create a 100 W incandescent bulb, using a figure of 13.8 lm/W from wikipedia ( http://en.wikipedia.org/wiki/Luminous_efficacy ), and 100 W, the luminous flux of the bulb is 100 W * 13.8 lm/W = 1380 lm.
It's definitely making more sense. However, the one thing that you still haven't clarified is what happens to base emission when you use emission scale?

For example, if I define base emission value to be RGB spectrum R=1000,G=1000,B=1000, that defines an emitter with spectral radiance in units of W m-3 sr-1. If I then set the emission scale for that material, does Indigo then normalize the RGB values and then set the luminous flux purely from the emission scale value, or do the two values (base emission and emission scale) work together some other way?

Also, what about blackbody spectra defined in base emission value? In the absence of the emission and emission scale parameters, does the spectral radiance value=1? How is the luminous flux calculated in this case?

What I am asking in a round about way is whether you can define a 100W incandescent emitter (say 2800K blackbody) WITHOUT using emission scale.

One last question that I don't think has been addressed: Can you use IES profiles with emitting materials? If so, how??
After defining the base_emission and emission of a material, the material will have a certain emission spectrum (spectral power distribution). If an emission_scale element is then defined, then a scaling factor will be applied to the whole spectrum, so that the measure as defined in the emission_scale element has the desired value. So the emission_scale basically acts as a scalar multiplier for the emission spectrum, with the multiplication factor determined by internal Indigo calculations.

Also, what about blackbody spectra defined in base emission value? In the absence of the emission and emission scale parameters, does the spectral radiance value=1? How is the luminous flux calculated in this case?
No, the spectral radiance value is not one. It's determined using Planck's law. The luminous flux of such an emission spectrum is determined in the usual way, by weighting by the luminosity curve.
What I am asking in a round about way is whether you can define a 100W incandescent emitter (say 2800K blackbody) WITHOUT using emission scale.
Sure, just integrate the emitted spectral radiance (as determined by Planck's law) over the hemisphere, over all wavelengths, and over the surface of the emitter, which will give you the total emitted power (100W). Then, assuming your undetermined variable is either the surface area of the light source, or the temperature of the light source, solve for that variable.
Hi Ono,

please can you show us the calculus for a sphere of diameter of 4 cm that emits light (say 2800K blackbody) in isotropic mode and an emitted power of 100W?

I need all equations so i can generalize (e.g. neon tube).

Thank you.

Delle

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