Hello everybody,

Do you know whether is possible (or how hard it would be) to read
photometric information of a "real" light (IES file) and create the 
corresponding POV light?

Thanks in advance.

pedro

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Pedro Rosas wrote:
>
> Do you know whether is possible (or how hard it would be) to read
> photometric information of a "real" light (IES file) and create the
> corresponding POV light?

What does an IES file look like? The intensity can be coded to the
alpha channel of a spherical image map which is mapped to a sphere
around a light source. 


_____________
Kari Kivisalo

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> 
> Pedro Rosas wrote:
> >
> > Do you know whether is possible (or how hard it would be) to read
> > photometric information of a "real" light (IES file) and create the
> > corresponding POV light?
> 
> What does an IES file look like? The intensity can be coded to the
> alpha channel of a spherical image map which is mapped to a sphere
> around a light source.

  Hmmm... I had a look at that topic in the past, and while I see how to
use color and distance information, I've no idea on how to relate light
intensity to POV-Ray light_sources... and of course I don't understand
your point about using alpha channel for that. Please, enlighten us!

-- 
Jaime Vives Piqueres

La Persistencia de la Ignorancia
http://www.ignorancia.org/

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in news:3BAB2703.1EFD7F22@engineer.com Kari Kivisalo wrote:

> What does an IES file look like?

http://www.ledalite.com/resources/software/index.html

"IES File Viewer" parses ies files and comes with a description of ies 
files 

"IES Photometry File" has ~400 ies files.

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Jaime Vives Piqueres wrote:
>
> I've no idea on how to relate light
> intensity to POV-Ray light_sources... 

You are free to choose any units and then interpret the results
based on this decision. Just remember that pov outputs only
integer values (0-1) so you will have to choose a scene dependant
scale factor to prevent overflows.

> and of course I don't understand
> your point about using alpha channel for that.

Or you can use the transmit channel of a pigment if the data
is red in and interpolated within pov script. I don't know
any other way to control the radiation distribution of a light
source. There was a patch for light sources which did essentially
the same thing.


_____________
Kari Kivisalo

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Thanks for the answers, but I have to admit I'm not quite following:
what if I know the luminance of a particular bulb (real) and I
want to model it in POV. Is there a way to traduce, say, candelas per
sqr meter, in POV units? 

Txs again!



Kari Kivisalo wrote:
> 
> Jaime Vives Piqueres wrote:
> >
> > I've no idea on how to relate light
> > intensity to POV-Ray light_sources...
> 
> You are free to choose any units and then interpret the results
> based on this decision. Just remember that pov outputs only
> integer values (0-1) so you will have to choose a scene dependant
> scale factor to prevent overflows.
> 
> > and of course I don't understand
> > your point about using alpha channel for that.
> 
> Or you can use the transmit channel of a pigment if the data
> is red in and interpolated within pov script. I don't know
> any other way to control the radiation distribution of a light
> source. There was a patch for light sources which did essentially
> the same thing.
> 
> _____________
> Kari Kivisalo

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Pedro Rosas wrote:
> Thanks for the answers, but I have to admit I'm not quite
> following: what if I know the luminance of a particular bulb
> (real) and I want to model it in POV. Is there a way to traduce,
> say, candelas per sqr meter, in POV units?

To elaborate Pedro's question, if 1 POV unit = 1 meter, how do you


('cuz I jest KNOW yer gonna say that it matters what your POV
units stand for)

-- 
Tim Cook
http://empyrean.scifi-fantasy.com

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