I hope someone can help me with a problem I'm having with illuminating my
scene with flourescent lights using radiosity.

I'm re-creating my living room in pov-ray, and the problem I'm having is
with the radiosity illumination of the flourescent lights. The lights are
basically made using 160*2.5 cm cylinders with white pigment and high
ambient. A cross-section of the location of the lights in the scene is in a
kind of like this:

  ___
 /
|
| * |
|___|
|   |

I can't seem to get them to illuminate the scene enough. The real-world
lights produce sufficent lighting, but the virtual ones don't. I've cranked
the ambient value of the lights up to pow(10,30), and still the
illumination is too dark. I tried using light sources in a line instead of
high ambient, but the results didn't look very realistic. I have been
trying for 3 days to try and solve this without any luck. Here is the
radiosity block from my scene:

  radiosity {
    pretrace_start 0.08
    pretrace_end   0.4
    count 1600

    nearest_count 8
    error_bound 1.0
    recursion_limit 2

    low_error_factor 0.5
    gray_threshold 0.0
    minimum_reuse 0.015
    brightness 1

    //max_sample -1000
    adc_bailout 0.01/pow(10,30)
    //always_sample off
    //normal on
    //media on
    }

I sure would like some help with this problem. I would post comparison
images in the binary group, if I had a digital camera and the web interface
allowed attatchments.

Rohan _e_ii

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"Rohan Bernett" <rox### [at] yahoocom> wrote in message
news:web.3ddaccae46e653f8b2769afa0@news.povray.org...
> I hope someone can help me with a problem I'm having with illuminating my
> scene with flourescent lights using radiosity.
>
> I'm re-creating my living room in pov-ray, and the problem I'm having is
> with the radiosity illumination of the flourescent lights. The lights are
> basically made using 160*2.5 cm cylinders with white pigment and high
> ambient.

You could try using a high diffuse value, since that is what radiosity will
be working with instead of the ambient. Although it isn't likely to be
completely right without actual light sources.
Your error_bound might have to be 1/10 to help with blotchiness. Your count
is pretty high, seems to me anyway because I typically use a count of under
1000 or even under 500.
Why is gray_threshold at 0 (off)? Are you trying to prevent color bleed,
thus perhaps dark things into the light? Something I'm unsure would be
affective or not.
--
Farewell,
Bob

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Rohan Bernett <rox### [at] yahoocom> wrote:
> I tried using light sources in a line instead of
> high ambient, but the results didn't look very realistic.

  You shouldn't dump a possible solution just because a first experiment
didn't succeed.
  Can you be more precise about what you tried and why it didn't look good?
Did you try with area_lights (which should be quite dense and naturally
use adaptiveness)?

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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On Tue, 19 Nov 2002 18:43:42 EST, "Rohan Bernett" <rox### [at] yahoocom>
wrote:

>I can't seem to get them to illuminate the scene enough. The real-world
>lights produce sufficent lighting, but the virtual ones don't. I've cranked
>the ambient value of the lights up to pow(10,30), and still the
>illumination is too dark. 

100 should be enough, even 10, just make sure you assign the same
value to max_sample as you assign to the ambient, otherwise you're
just limiting the brightness.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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"hughes, b." <omn### [at] charternet> wrote in message news:3ddb17cf@news.povray.org...
> Why is gray_threshold at 0 (off)? Are you trying to prevent color bleed,
> thus perhaps dark things into the light? Something I'm unsure would be
> affective or not.

gray_threshold at 0 leads to maximum colour-bleed doesn't it? Not 'off'

Andy Cocker

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How about raising recursion_limit a little? If
I'm not mistaken, thats what sets a limit for
light bouncing off of other areas (so your "light-source"
might light the lamp (limit 1) bounce off and hit another
area (limit 2), and thats it. But I could be wrong. Try raising
it to 3 or 4, maybe even 5, and see what happens...


--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

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"Andrew Cocker" <mai### [at] andrewcockercouk> wrote in message
news:3ddb7c87$1@news.povray.org...
>
> "hughes, b." <omn### [at] charternet> wrote in message
news:3ddb17cf@news.povray.org...
> > Why is gray_threshold at 0 (off)? Are you trying to prevent color bleed,
> > thus perhaps dark things into the light? Something I'm unsure would be
> > affective or not.
>
> gray_threshold at 0 leads to maximum colour-bleed doesn't it? Not 'off'

Oops. I think I see my mistake. I have been misinterpreting the
documentation on it. Been using very low non-zero values for it all this
time. The part where it says:

"At 0%, this feature does nothing. At 100%, you always get white/gray
ambient light, with no hue."

Obviously it must actually be saying that 0 is same as default and so makes
no change. This could need a rewording because what I think it really means
is that 0% (=0?) is that gray_threshold is not active and thereby not
applying graying. Or something to that effect.

Sure am glad you questioned me about that.

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In article <3ddb17cf@news.povray.org>,
 "hughes, b." <omn### [at] charternet> wrote:

> You could try using a high diffuse value, since that is what radiosity will
> be working with instead of the ambient. Although it isn't likely to be
> completely right without actual light sources.

Since he is using radiosity as a lighting source, the high ambient is 
needed. Diffuse won't do anything if there's no light to diffuse, your 
advice would give a black image.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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"Christopher James Huff" <chr### [at] maccom> wrote in message
news:chr### [at] netplexaussieorg...
> In article <3ddb17cf@news.povray.org>,
>  "hughes, b." <omn### [at] charternet> wrote:
>
> > You could try using a high diffuse value, since that is what radiosity
will
> > be working with instead of the ambient. Although it isn't likely to be
> > completely right without actual light sources.
>
> Since he is using radiosity as a lighting source, the high ambient is
> needed. Diffuse won't do anything if there's no light to diffuse, your
> advice would give a black image.

I see, thanks Christopher. I almost mentioned ambient 1 instead of very high
ambient values because I wasn't sure how the higher than 1 value might
negatively affect the outcome of the render.
--
Farewell,
Bob

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"Rohan Bernett" <rox### [at] yahoocom> wrote in
news:web.3ddaccae46e653f8b2769afa0@news.povray.org 

[...]

I alsow played with pure-ambient lights, but there are terribly slow to 
render.

In my case the solution was - to use assumed_gamma 1.0 (or even 0.7)
Other thing - swith for a test all textures to pigment rgb .9 and difffuse 
.8 or .9

-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

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