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From: Neil Mercer
Subject: A Lighting Question
Date: 12 Jan 1999 16:13:30
Message: <369bbafa.0@news.povray.org>
Hi there,

    I'm trying to model (amongst other things) a LED.  Building the shape
has not really been a problem, but now I want to be able to include a light
inside it so I can make the LED light up (obviously).  I'm having trouble
getting the light to look right.  So far it either floods the scene with
light (i.e. too intense) or merely makes the LED structure look like it has
a shiny surface texture.  What I would like is that nice glow that looks so
simple and easy!

    Also, at this stage I've been colouring the LED itself and using a white
(or near-white light).  Would it be better to have a clear LED and a
coloured light?

Thanks in advance for any help.

Neil.


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From: Ken
Subject: Re: A Lighting Question
Date: 12 Jan 1999 16:27:05
Message: <369BBDAE.149C5C86@pacbell.net>
Neil Mercer wrote:

> Hi there,
>
>     I'm trying to model (amongst other things) a LED.  Building the shape
> has not really been a problem, but now I want to be able to include a light
> inside it so I can make the LED light up (obviously).  I'm having trouble
> getting the light to look right.  So far it either floods the scene with
> light (i.e. too intense) or merely makes the LED structure look like it has
> a shiny surface texture.  What I would like is that nice glow that looks so
> simple and easy!
>
>     Also, at this stage I've been colouring the LED itself and using a white
> (or near-white light).  Would it be better to have a clear LED and a
> coloured light?
>
> Thanks in advance for any help.
>
> Neil.

  Instead of thinking of it as a light source think instead of it as
a glowing object. One trick you might try is making your LED
texture semi-transpearent. Then inside of it plant a seed that
will be the glow source. If you add a very high ambient finish
to it it will more realisticaly model a glowing effect than a light
source will.

example:
assumes your LED is 1 unit in size adjust accordingly.

object{LED
 pigment{rgbf<1,0,0,.8}}

sphere{<0,0,0>,0.1
 pigment{rgb<1,0,0>}
  finish{ambient 3}// adjust to desired effect
}

Ken Tyler


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From: Thomas Lake
Subject: Re: A Lighting Question
Date: 12 Jan 1999 19:15:01
Message: <369BE55C.F4625028@home.com>
I have another good way to model LED's although its no good if you want to be able
to see the entire LED itself. This is best for modeling the LED's you see on
electronics like the three LED's on your CPU hard drive, turbo and power. What you
do is create, using CSG's a small room behind where you want the LED to be, make
this room have a 100% reflective texture. Then cut a small hole the shape of the
LED from the hole to the surface of you object. Now create a small coloured panel
and place it in front of the room, but a little away from the surface of the
object. Now create a light and place it in the room. When rendered this creates a
very realistic glowing effect. Below is a picture of mine which shoes this effect,
look at the CPU case, and the keyboard.

___________     _     |____Surface of object.
|                     |__|_|__|
|  Small Room     |  |________Coloured LED panel
|                      __|_|__
|___________|   |_|   |
                                 |


Ken wrote:

> Neil Mercer wrote:
>
> > Hi there,
> >
> >     I'm trying to model (amongst other things) a LED.  Building the shape
> > has not really been a problem, but now I want to be able to include a light
> > inside it so I can make the LED light up (obviously).  I'm having trouble
> > getting the light to look right.  So far it either floods the scene with
> > light (i.e. too intense) or merely makes the LED structure look like it has
> > a shiny surface texture.  What I would like is that nice glow that looks so
> > simple and easy!
> >
> >     Also, at this stage I've been colouring the LED itself and using a white
> > (or near-white light).  Would it be better to have a clear LED and a
> > coloured light?
> >
> > Thanks in advance for any help.
> >
> > Neil.
>
>   Instead of thinking of it as a light source think instead of it as
> a glowing object. One trick you might try is making your LED
> texture semi-transpearent. Then inside of it plant a seed that
> will be the glow source. If you add a very high ambient finish
> to it it will more realisticaly model a glowing effect than a light
> source will.
>
> example:
> assumes your LED is 1 unit in size adjust accordingly.
>
> object{LED
>  pigment{rgbf<1,0,0,.8}}
>
> sphere{<0,0,0>,0.1
>  pigment{rgb<1,0,0>}
>   finish{ambient 3}// adjust to desired effect
> }
>
> Ken Tyler


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Attachments:
Download 'computer desk.jpg' (43 KB)

Preview of image 'computer desk.jpg'
computer desk.jpg


 

From: Thomas Lake
Subject: Re: A Lighting Question
Date: 12 Jan 1999 19:17:40
Message: <369BE5AF.86E398A2@home.com>
Opps Sorry about the illustraion, it got messed up when it posted it.

Thomas Lake wrote:

> I have another good way to model LED's although its no good if you want to be able
> to see the entire LED itself. This is best for modeling the LED's you see on
> electronics like the three LED's on your CPU hard drive, turbo and power. What you
> do is create, using CSG's a small room behind where you want the LED to be, make
> this room have a 100% reflective texture. Then cut a small hole the shape of the
> LED from the hole to the surface of you object. Now create a small coloured panel
> and place it in front of the room, but a little away from the surface of the
> object. Now create a light and place it in the room. When rendered this creates a
> very realistic glowing effect. Below is a picture of mine which shoes this effect,
> look at the CPU case, and the keyboard.
>
> ___________     _     |____Surface of object.
> |                     |__|_|__|
> |  Small Room     |  |________Coloured LED panel
> |                      __|_|__
> |___________|   |_|   |
>                                  |
>
> Ken wrote:
>
> > Neil Mercer wrote:
> >
> > > Hi there,
> > >
> > >     I'm trying to model (amongst other things) a LED.  Building the shape
> > > has not really been a problem, but now I want to be able to include a light
> > > inside it so I can make the LED light up (obviously).  I'm having trouble
> > > getting the light to look right.  So far it either floods the scene with
> > > light (i.e. too intense) or merely makes the LED structure look like it has
> > > a shiny surface texture.  What I would like is that nice glow that looks so
> > > simple and easy!
> > >
> > >     Also, at this stage I've been colouring the LED itself and using a white
> > > (or near-white light).  Would it be better to have a clear LED and a
> > > coloured light?
> > >
> > > Thanks in advance for any help.
> > >
> > > Neil.
> >
> >   Instead of thinking of it as a light source think instead of it as
> > a glowing object. One trick you might try is making your LED
> > texture semi-transpearent. Then inside of it plant a seed that
> > will be the glow source. If you add a very high ambient finish
> > to it it will more realisticaly model a glowing effect than a light
> > source will.
> >
> > example:
> > assumes your LED is 1 unit in size adjust accordingly.
> >
> > object{LED
> >  pigment{rgbf<1,0,0,.8}}
> >
> > sphere{<0,0,0>,0.1
> >  pigment{rgb<1,0,0>}
> >   finish{ambient 3}// adjust to desired effect
> > }
> >
> > Ken Tyler
>
>   ------------------------------------------------------------------------
>  [Image]


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From: Simon de Vet
Subject: Re: A Lighting Question
Date: 12 Jan 1999 21:04:55
Message: <369BFF9B.ACC9CD44@istar.ca>
Neil Mercer wrote:

> Hi there,
>
>     I'm trying to model (amongst other things) a LED.  Building the shape
> has not really been a problem, but now I want to be able to include a light
> inside it so I can make the LED light up (obviously).  I'm having trouble
> getting the light to look right.  So far it either floods the scene with
> light (i.e. too intense) or merely makes the LED structure look like it has
> a shiny surface texture.  What I would like is that nice glow that looks so
> simple and easy!
>
>     Also, at this stage I've been colouring the LED itself and using a white
> (or near-white light).  Would it be better to have a clear LED and a
> coloured light?

May I reccomend not trying to make a light in the bulb. instead, make the bulb
with a high ambiant level, so it looks lit (without any light source) then place
the coloured source inside, with the bulb set to "No Shadow" so the light will
shine through. Works much better than trying to get the bulb to actually filter
the light, which is terrible to get to look right...

Also, for a glow you might want to play around with the lens flares, or for just
emitted light, set a fade distance so it will light up just the nearby
neighborhood, and not the entire scene.

If this is confusing (not good at explaining things :)  I can make up a little
.mdl with this example.....

Simon
http://home.istar.ca/~sdevet


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From: Nieminen Mika
Subject: Re: A Lighting Question
Date: 13 Jan 1999 07:08:46
Message: <369c8cce.0@news.povray.org>
In povray.newusers Neil Mercer <nme### [at] mercersconz> wrote:
:     I'm trying to model (amongst other things) a LED.  Building the shape
: has not really been a problem, but now I want to be able to include a light
: inside it so I can make the LED light up (obviously).  I'm having trouble
: getting the light to look right.  So far it either floods the scene with
: light (i.e. too intense) or merely makes the LED structure look like it has
: a shiny surface texture.  What I would like is that nice glow that looks so
: simple and easy!

  I don't know why I'm maintaining a povray VFAQ when nobody is using it...

  Anyways, the answer to this question is, too, in the VFAQ.

http://www.cs.tut.fi/~warp/povVFAQ.html#brightobjects

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/


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From: Johannes Hubert
Subject: Re: A Lighting Question
Date: 13 Jan 1999 12:59:47
Message: <369cdf13.0@news.povray.org>
Thomas Lake wrote in message <369BE55C.F4625028@home.com>...
>I have another good way to model LED's
[snip]
>What you
>do is create, using CSG's a small room behind where you want the LED to be,
make
>this room have a 100% reflective texture. Then cut a small hole the shape
of the
>LED from the hole to the surface of you object.
[snip]

That idea seems sound at first glance, but when viewed with the mechanics of
a raytracer (and especially POV-Ray) in mind, one sees, that it is not the
best solution to the problem: The outcome may be the one that is wished for
(as can be seen in the image you posted), but for the wrong reasons, and at
the cost of increased rendertime.

I'll try to explain why:

I see why you would go for 100% reflectiveness: Because it would model
reality closest, with the "small room" catching the light of the lightsource
and casting it all out of the little hole, like the reflector of a lamp,
making the LED shine brightly.

Only this doesn't work in POV-Ray :-)

If it would, then POV-Ray would be able to do specular reflection / indirect
lighting, which it can't do (if you don't count the very interesting project
Nathan Kopp has in the works).
So using the 100% reflection has only one effect: Pushing up render time
unnecessarily, but the visible outcome of the image will not be changed by
it.

Instead you could simply:
a) Color the walls of the "small room" white and let the colored lightsource
make them appear in the right color, or
b) Color the walls of the "small room" in the color of the LED and use a
white lightsource, or... :

Actually, if you don't want to have the LED to throw light on anything (like
in your rendered image, where the LEDs are only seen as bright spots, but do
not throw light on anything), then it would cut down on rendertime even
more, if you leave out the light source totally, which leaves option "c"
(quite close Ken's suggestion):

c) Color the walls of the "small room" in the color of the LED and give them
a high ambient value, don't use a lightsource at all...

Please excuse my dismissal of your otherwise very creative idea :-) but I
thought it would save some people some time if I explained a bit...

So long,
Johannes.


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From: Johannes Hubert
Subject: Re: A Lighting Question
Date: 13 Jan 1999 13:10:15
Message: <369ce187.0@news.povray.org>
Nieminen Mika wrote in message <369c8cce.0@news.povray.org>...
>
>  I don't know why I'm maintaining a povray VFAQ when nobody is using it...

Huhh?
This is the strangest post of a long time!

It sounds like:

"Hey, we need a VFAQ, only we are all to busy to do one. Who wants to do
it?"
[nobody raising a hand]
"Nieminen! What about you?"
"No, thanks. I have no time either..."
"Oh, pleeeease!"
"No, really, sorry!"
"Yes you can do it! Pleeease! We all promise that we will read it all the
time too!!!"
"Promise?"
"Yes, 'Promise'! We'll read it like a bible, nobody will ignore it!"
"Ok, ok, but only under that condition!"
"Thank you, thank you, we love you Nieminen! ..."

Well, I assume that this is not quite how it was, is it? ;-)

Please face reality:
People will always ask questions that are already answered in some FAQ
somewhere.
You then have three options:

1. Ignore the question, and think "he'll find the answer in the FAQ or some
kind soul will help him"
2. Point the person to the FAQ
3. Berate the person about not reading the FAQ and appear really childish by
doing this...

(well, actually I could think of some more possible options, like "trying to
find out where the sucker lives and then bombing his mailbox with a big
fire-cracker", or "getting hold of his FAX number and faxing him 101 copies
of the FAQ - with fontsize 36"... :-)


Greetings,
Johannes.


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From: Nieminen Mika
Subject: Re: A Lighting Question
Date: 13 Jan 1999 14:58:23
Message: <369cfadf.0@news.povray.org>
In povray.newusers Johannes Hubert <jhu### [at] algonetse> wrote:
: Please face reality:
: People will always ask questions that are already answered in some FAQ
: somewhere.
: You then have three options:

: 1. Ignore the question, and think "he'll find the answer in the FAQ or some
: kind soul will help him"
: 2. Point the person to the FAQ
: 3. Berate the person about not reading the FAQ and appear really childish by
: doing this...

  But this is not "a FAQ". This is "The FAQ". No, no, it's "The VFAQ" ;)
  You talk about "some FAQ somewhere". Well, I have never seen any FAQ
anywhere about povray. I have never seen anyone answering something like
"the answer is in the FAQ located at...".
  A have also seen that people ask same questions again and again. No matter
how many times you answer, they will ask the same question again. A question
which isn't answered anywhere.
  So this is why I wanted to put those answers in one file so that when
someone asks the same question again, you can save time and typing by
answering just "http://something/povVFAQ.html#question".
  I threw the idea on the news, and the feedback was very encouraging. People
sent me lots of questions and answers. I also received feedback from people
who have read it and liked it and who learnt many things about it. It
seemed like it would be "The FAQ".
  Now it is out there, and it's the only one I know.
  When somebody asks a question in the FAQ, I regularly answer with a proper
URL to the exact location of the answer. Sometimes, specially at the
beginning, some people answered to questions with the URL to the FAQ (but
not with the exact location to the answer, ie. with the #parameter after
the URL).
  Now I'm the only one who answers with the VFAQ. Even those who sent me
questions and asnwers have stopped using it (you are one of them, shame on
you! ;) ).

  Your reply sounded to me like you were insinuating that I'm a little bit
hypocrite. Well, maybe that's so, but I sincerely thought that people,
specially those who contributed in making the VFAQ, were really interested
in it. I sincerely thought that I was making some worthy for the pov
community.
  It's a bit discouraging that one of the contributors answers this way...
It's a bit disappointing that my work seems to be futile.
  Sorry, I'm not blaming you or anyone else. I'm just awakening to see the
cruel world...

-- 
main(i){char*_="BdsyFBThhHFBThhHFRz]NFTITQF|DJIFHQhhF";while(i=
*_++)for(;i>1;printf("%s",i-70?i&1?"[]":" ":(i=0,"\n")),i/=2);} /*- Warp. -*/


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From: Ken
Subject: Re: A Lighting Question
Date: 13 Jan 1999 15:42:57
Message: <369D04D7.E5E7C616@pacbell.net>
Nieminen Mika wrote:

>   Sorry, I'm not blaming you or anyone else. I'm just awakening to see the
> cruel world...

I'm guilty as charged. I'm sorry ! I will endeavor to remember to use
your VFAQ when appropriate. Please forgive me. I'm unworthy.
It's not a wasted resource. Please have patience with us. Thank you.
What you have done is a good thing. The community supports your
efforts. Please do not take our short termed memories as an indication
of the potential of the VFAQ. None is better for the answers it contains.
I ask for another chance to redeem myself. You are powerful and wise.
Get well soon. I will make the VFAQ my start up home page so as not
to forget it's tremendous value. Just think of the time it will save me in
typing alone. Wow ! Why hasn't someone else come up with such a
great thing before is beyond me. Remain dauntless und unswerving in
the face of overwhelming odds. I apologize for my short comings.
I will make amends if you will allow me.

Have I blown enough sunshine up your yet yet ?

--
Ken Tyler

tyl### [at] pacbellnet


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