Do you think is possible to implement a new function for a light source,
with rays function of solid angle (seeIES standard). I different words,
having the possibility of controlling the energy of rays in relation with
horizontal and vertical angle. It would be very usefull for modelling


Thank you all.

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> Do you think is possible to implement a new function for a light source,
> with rays function of solid angle (seeIES standard). I different words,
> having the possibility of controlling the energy of rays in relation with
> horizontal and vertical angle. It would be very usefull for modelling


This could probably be done in SDL with a sphere with a filtering pigment
around a normal light source, unless I misunderstand.

 - Slime
 [ http://www.slimeland.com/ ]

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Gianluca Massaccesi wrote:
> Do you think is possible to implement a new function for a light source,
> with rays function of solid angle (seeIES standard). I different words,
> having the possibility of controlling the energy of rays in relation with
> horizontal and vertical angle. It would be very usefull for modelling


If you are working with isosurfaces (and if you don't care about
shadows), then you can calculate how much a light source illuminates
a point on the surface by using functions in SDL. (I.e. you don't
need to patch POV-Ray to do this.)

I once used such a technique to make a few simple images.
Some of them can be found in this thread:

http://news.povray.org/povray.binaries.images/thread/%3CXns93A4378303A9Ftorolavkhotmailcom%40204.213.191.226%3E/
or http://tinyurl.com/ytkvh

It should also be possible to do something similar with meshes
made up of (small) triangles.


Tor Olav

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Tor Olav Kristensen wrote:
> Gianluca Massaccesi wrote:
> 
>> Do you think is possible to implement a new function for a light source,
>> with rays function of solid angle (seeIES standard). I different words,
>> having the possibility of controlling the energy of rays in relation with
>> horizontal and vertical angle. It would be very usefull for modelling

>> purpose.
> 
> 
> If you are working with isosurfaces (and if you don't care about
> shadows), then you can calculate how much a light source illuminates
> a point on the surface by using functions in SDL. (I.e. you don't
> need to patch POV-Ray to do this.)
 >
 > I once used such a technique to make a few simple images.
...

I forgot to mention that you would have to make a function that
describes the energy distribution at different angles around (or
relative to ?) the light source.

The source code for the mentioned images can be found here.

http://news.povray.org/povray.text.scene-files/thread/%3CXns93A54E262AE2torolavkhotmailcom%40204.213.191.226%3E/
or http://tinyurl.com/2dbua

(It might give you some hints about how to start attacking this
problem.)


Tor Olav

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in news:4044ef3b$1@news.povray.org Slime wrote:

> This could probably be done in SDL with a sphere with a filtering
> pigment around a normal light source, unless I misunderstand.
> 

The hard part would probably be to convert luminance file to functions. 
Ian Ashdown made a parser available for parsing IESNA LM-63 and similar 
files, maybe that could be a start.

Also if I remember well, there was somebody who patched povray in a way 
that it could work these IES files, but the code was never published. 
Can't find the discussion, it was about a year (or more) ago.

I would realy welcom a POV-Ray feature that could read and deal with such 
files directly. Many manufacturers of lighting systems make these data 
available.


Ingo

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