Hi,

am I to understand that photons are only shot by light_sources?
Or does anyone have a tip to extend the photons to radiosity?

Markus
-- 

 Ich nicht eine Sekunde!!!" H. Heinol in Val Thorens

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On Thu, 18 Mar 1999 12:21:22 +0100, Markus Becker 
	<bec### [at] zessuni-siegende> wrote:
>Hi,
>
>am I to understand that photons are only shot by light_sources?
>Or does anyone have a tip to extend the photons to radiosity?

When you say radiosity, are you talking about the "box with no 
lights" thread from a while ago?  

Terminology nitpick: radiosity is a term for a specific global
illumination system.  Photon mapping is a term for a different
global illumination system.  If you're using a photon map, you 
probably shouldn't be using POV-Ray's "radiosity" features.

Perhaps you could get by with an area light.  That assumes that
the photon mapping patch works (correctly) with area lights, of
course.

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Ron Parker wrote:
> 
> On Thu, 18 Mar 1999 12:21:22 +0100, Markus Becker
>         <bec### [at] zessuni-siegende> wrote:
> >Hi,
> >
> >am I to understand that photons are only shot by light_sources?
> >Or does anyone have a tip to extend the photons to radiosity?
> 
> When you say radiosity, are you talking about the "box with no
> lights" thread from a while ago?
> 
> Terminology nitpick: radiosity is a term for a specific global
> illumination system.  Photon mapping is a term for a different
> global illumination system.  If you're using a photon map, you
> probably shouldn't be using POV-Ray's "radiosity" features.

Well, right now photon mapping only does specular and refractive caustic
lighting, while 'radiosity' does indirect diffuse lighting... so right
now they are pretty orthogonal features, so you can use them together
without problems.

> Perhaps you could get by with an area light.  That assumes that
> the photon mapping patch works (correctly) with area lights, of
> course.

Sorry, but photons don't work right with area lights... eventually they
will... I haven't taken the time to program that part yet.  ;-)
All lights are currently treated like point lights.

-Nathan

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On Thu, 18 Mar 1999 09:45:53 -0500, Nathan Kopp <Nat### [at] Koppcom> wrote:
>Well, right now photon mapping only does specular and refractive caustic
>lighting, while 'radiosity' does indirect diffuse lighting... so right
>now they are pretty orthogonal features, so you can use them together
>without problems.

I stand corrected.  Photon mapping can do better diffuse interreflection
(IMO) than does POV's "radiosity," though, so I wonder if you're having 
any success with getting that part implemented?

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Ron Parker wrote in message <36f0fe89.0@news.povray.org>...
>
>Terminology nitpick: radiosity is a term for a specific global
>illumination system.  Photon mapping is a term for a different
>global illumination system.

And POV doesn't use eiter of them for its global illumination. POV's
"radiosity" is actually closer to photon mapping, IMO.

Margus

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Just a thought, but something radiosity-like may be possible with the
existing photon patch (It should be noted though that I do not have the
photon patch because of a lack of processing power, I don't even have
the patience to do extensive traditional ray tracing on my PC. However,
I have followed the developement of the patch and have a pretty good
idea of how it works).

Here goes:
The diffuse interreflection simulated by radiosity and Pov Ray's
distributed raytracing is caused by imperfections on the reflecting
surface scattering the light in every direction. So why not do just
that. By creating a surface normal of something like bumps and scaling
the pattern to a very small scale, it may be possible to have the
reflected photons scatter to illuminate the scene. This has the one
disadvantage of requiring a large number of photons. HOWEVER, as I
understand it, the photon patch uses a variable to control how many
photons are gathered from the neighbouring regions to determine the
illumination of a point. Since global illumination does not require the
same precision as caustics, it may be possible to increase the area that
photons are gathered from and therefore decrease the total number of
photons required for the image to look globally illuminated.

Wait! It's not as crazy as it sounds!
I once used a similar technique to fake blurry reflections and the
results were pretty good. Also, this is essentially a modification of
what Pov Ray already uses to do global illumination.

Well, that's just a thought, anyone care to give it a shot?

BTW: Before the photon patch, people were always complaining that they
couldn't do disco balls. Now we have the means but I have yet to see one
in p.b.i, what gives?

-- 
Chris Maryan
mailto:cma### [at] geocitiescom
***
Will work for cash.
***
Any ideas presented in this message
are mine, mine and all mine. So if you
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Gimme, gimme, gimme.

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>photon patch because of a lack of processing power,

neither do any of us!! (well not as miuch as we would like)

try leaving it to render overnight, works for me :)

Rick

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Thanks, this answers my question.

Markus

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Chris Maryan wrote:
X-Mozilla-Status: 0009 the photon patch, people were always complaining that
they
> couldn't do disco balls. Now we have the means but I have yet to see one
> in p.b.i, what gives?

You know what? I poitned the same erlier in p.b.i. :-)
I'm still waiting(working on my new linux system. *yumma*, as well as playing
with scnes lit only with reflective caustics...)

-- 
//Spider
        [ spi### [at] bahnhofse ]-[ http://www.bahnhof.se/~spider/ ]
What I can do and what I could do, I just don't know anymore
                "Marian"
        By: "Sisters Of Mercy"

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Rick wrote:
> >photon patch because of a lack of processing power,
> 
> neither do any of us!! (well not as miuch as we would like)
> 
> try leaving it to render overnight, works for me :)
> 
> Rick

Remember those original overdrive chips that turned a 486-66 to a
pentium-83. I have one of those and 32MB RAM. Overnight for you means
three days for me. Maybe I'll take a shot at doing something simple like
a mirrored ball on a checkered plane :-)

-- 
Chris Maryan
mailto:cma### [at] geocitiescom
***
Will work for cash.
***
Email me if you are interested in donating
to the Chris Maryan needs money fund.
We will also accept donations to the Chris
needs a Pentium II or SGI workstation 
fund and the Chris needs a car fund.

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