Hello. I'm looking for a bit of advice or a tutorial on lighting a room.
The problem I seem to be having is getting the ceiling to be properly
illuminated. I have the camera situated at "eye level" and looking straight
ahead.
Depending on where I put the lights the floor & walls show up fine, but the
ceiling is black and/or very dark. Reasonably sure that light just isn't
hitting it...

I've tried placing a standard (point) light_source at ceiling height, and I've
tried placing a light source "behind" the camera.

Any hints or any simple little examples floating around somewhere? Something
basic with just a floor, ceiling, and some walls would be greatly appreciated.

Ideally, I'm looking to place a couple recessed panel lights, but one step at a
time for a newbie, right?

Thanks for your help.
-Alex

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"bardgaijin" <nomail@nomail> wrote in message 
news:web.4874b3da9401de58c86a64a40@news.povray.org...
> Hello. I'm looking for a bit of advice or a tutorial on lighting a room.
> The problem I seem to be having is getting the ceiling to be properly
> illuminated. I have the camera situated at "eye level" and looking 
> straight
> ahead.
> Depending on where I put the lights the floor & walls show up fine, but 
> the
> ceiling is black and/or very dark. Reasonably sure that light just isn't
> hitting it...
>
> I've tried placing a standard (point) light_source at ceiling height, and 
> I've
> tried placing a light source "behind" the camera.

It should be below the ceiling height by some distance, otherwise it won't 
cast any light directly onto the ceiling.

>
> Any hints or any simple little examples floating around somewhere? 
> Something
> basic with just a floor, ceiling, and some walls would be greatly 
> appreciated.
>
> Ideally, I'm looking to place a couple recessed panel lights, but one step 
> at a
> time for a newbie, right?
>
> Thanks for your help.
> -Alex

You probably want to read the section on 'Light Fading' in the help (section 
3.4.7.9 in the Windows help file).

You might like to try playing with the settings in the simple example below. 
The main ones are probably the fade_distance and fade_power on the light 
which make the light act more like a real light.

Much of the light in a room is reflected off other surfaces. You can emulate 
that using the reflection setting on the finish of the various objects in 
the room or you can approximate it by giving poorly lit surfaces some 
ambience. If you need just the ceiling to be brighter then define it as a 
separate object and you can give it its own ambient setting. If you are 
using recessed lighting built into the ceiling you'll probably have to use 
the ambient setting to get any light shining off the ceiling because none 
will fall on it directly.

I find that making surfaces a little rough using a small agate setting on 
the normal can also make quite a big difference with interior scenes.

To get very realistic lighting there are a very large number of options 
available in POV-Ray and there are quite a number of tutorials on the 
different options and approaches. Once you've got a scene that's close to 
what you want it can be helpful to post an image on povray.binaries.images 
that illustrates any specific lighting problems to seek specific advice.

Regards,
Chris B.

camera {location <0,1.7,-1.2> look_at <0,1.7,0> angle 90}
light_source {<0,1.9 ,0>, rgb 0.7
  fade_distance 4
  fade_power 1
}
box {<-2,0,-2>,<2,2.3,2>
  pigment {rgb 1}
  normal {agate 0.05 scale 0.01}
  finish {ambient 0.5}
}

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"bardgaijin" <nomail@nomail> wrote:
> Hello. I'm looking for a bit of advice or a tutorial on lighting a room.
> The problem I seem to be having is getting the ceiling to be properly
> illuminated. I have the camera situated at "eye level" and looking straight
> ahead.
> Depending on where I put the lights the floor & walls show up fine, but the
> ceiling is black and/or very dark. Reasonably sure that light just isn't
> hitting it...
>
> I've tried placing a standard (point) light_source at ceiling height, and I've
> tried placing a light source "behind" the camera.
>
> Any hints or any simple little examples floating around somewhere? Something
> basic with just a floor, ceiling, and some walls would be greatly appreciated.
>
> Ideally, I'm looking to place a couple recessed panel lights, but one step at a
> time for a newbie, right?
>
> Thanks for your help.
> -Alex

Maybe radiosity will help. Hildur Kolbrun Andresdottir has an excellent tutorial
on it on http://www.simnet.is/hildurka/content/tut1page.htm

(sorry, don't know how to turn URL into a link)

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> 
> (sorry, don't know how to turn URL into a link)
> 
Thunderbird does this automatically
-- 
the ultimate time-killer:
+a0.0 +am2 +r9

Johnny D

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bardgaijin nous illumina en ce 2008-07-09 09:00 -->
> Hello. I'm looking for a bit of advice or a tutorial on lighting a room.
> The problem I seem to be having is getting the ceiling to be properly
> illuminated. I have the camera situated at "eye level" and looking straight
> ahead.
> Depending on where I put the lights the floor & walls show up fine, but the
> ceiling is black and/or very dark. Reasonably sure that light just isn't
> hitting it...
> 
> I've tried placing a standard (point) light_source at ceiling height, and I've
> tried placing a light source "behind" the camera.
> 
> Any hints or any simple little examples floating around somewhere? Something
> basic with just a floor, ceiling, and some walls would be greatly appreciated.
> 
> Ideally, I'm looking to place a couple recessed panel lights, but one step at a
> time for a newbie, right?
> 
> Thanks for your help.
> -Alex
> 
> 
> 
> 
> 
If your light is very close to the ceiling, you'll only have a very small area 
visibly lighted. The rest does receive light, but at a very shalow angle. When 
the incidance angle of your light is shalow, the light is spread ofer a larger 
surface, maling it look that much weaker.

If your light is at the same level as the ceiling, and there is no cavity at the 
light's location, you may get splotchy lighting. Example:
plane{y, 10 texture{Some_Texture}} // A ceiling
light_source{<10,10,-5 rgb 1} // A light coincident with the ceiling.
Also, this light won't light the ceiling as it's rays are parallel with the 
surface to be illuminated.

If your light is encased into the ceiling, the ceiling won't receive any.

Things you can try:
Put another light, relatively dim, above the room and add "double_illuminate" to 
the ceiling. It will fake the light bouncing back up to the ceiling... to a point.
Try lowering your light. That way, the light will hit the ceiling at a less 
shalow angle.

Keep your scene almost unchanged but with the following:

#default{finish{ambient 0 diffuse 0.8}}
//This will remove the default ambient from the finishes, and increase the 
diffuse value to compansate.
global_settings{radiosity{}}
//This turn on the radiosity feature usine all default settings.

To get an even more realistic lighting, you should use light fading.
Use fade_power 2 and fade_distance Some_Value. You may need to increase the 
intensity of your light(s), maybe even by a factor of 100 or more if you chose a 
short fade_distance.
fade_power 2 use the inverse square that you find in real life.

-- 
Alain
-------------------------------------------------
Congregationalist: Shit that happens to one person is just as good as shit that 
happens to another.

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