Something which troubles me is that when I put a light source near
a surface (such as a ceiling), the rest of the room is illuminated
but the surface proximal to the light remains unlit, even when I
turn on radiosity.  What settings can I use to fix this without
having to 'cheat' and hover the light in the centre of the space?

-- 
Tim Cook
http://empyrean.scifi-fantasy.com

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Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
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"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote in message
news:3BBB9A9D.55F8BDF6@scifi-fantasy.com...
> Something which troubles me is that when I put a light source near
> a surface (such as a ceiling), the rest of the room is illuminated
> but the surface proximal to the light remains unlit, even when I
> turn on radiosity.  What settings can I use to fix this without
> having to 'cheat' and hover the light in the centre of the space?

Use a high ambient of 0.5 or more, about the only way around it I know of.
If you raise diffuse really high, that can do it somewhat, as long as
radiosity is being used but you also get extreme saturation at the immediate
location of the light source too.  One of those things you must adjust until
you get the right look.  A lot depends on the kind of surface you have for a
ceiling too, whether normals or isosurface or whatever.

POV-Ray isn't as adept as some professional ray tracers I guess (hmm, could
that be?;-)), there are ones which mimic lighting better from what I've read
others say and seen examples of on the www.

Bob H.

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"Timothy R. Cook" wrote:
> 
> Something which troubles me is that when I put a light source near
> a surface (such as a ceiling), the rest of the room is illuminated
> but the surface proximal to the light remains unlit, even when I
> turn on radiosity.

Have a look at cornell.pov in 3.5 beta scenes or
http://www.pp.htv.fi/kkivisal/c/compress.htm

As the cornell image proves povray can do really
goog lighing simulation within the limits of
the lighting model (no BDRF).

_____________
Kari Kivisalo

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Timothy R. Cook <tim### [at] scifi-fantasycom> wrote:
: Something which troubles me is that when I put a light source near
: a surface (such as a ceiling), the rest of the room is illuminated
: but the surface proximal to the light remains unlit

  It doesn't "remain unlit". It's just that the angle of incidence of the
light on the surface is so small that the diffuse illumination is very dim.
  This would also happen in real life if you had a room with walls and floor
which don't reflect light (but which you can somehow see anyways).
  The reason why the ceiling is illuminated as well is because light reflects
from the floor and walls and illuminates the ceiling.

: even when I turn on radiosity.

  That's just a matter of tuning the parameters. You may want to pump up
the diffuse component of the room and/or the brightness of the radiosity.

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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On 4 Oct 2001 05:29:44 -0400, Warp wrote:
>Timothy R. Cook <tim### [at] scifi-fantasycom> wrote:
>: Something which troubles me is that when I put a light source near
>: a surface (such as a ceiling), the rest of the room is illuminated
>: but the surface proximal to the light remains unlit
>
>  It doesn't "remain unlit". It's just that the angle of incidence of the
>light on the surface is so small that the diffuse illumination is very dim.
>  This would also happen in real life if you had a room with walls and floor
>which don't reflect light (but which you can somehow see anyways).
>  The reason why the ceiling is illuminated as well is because light reflects
>from the floor and walls and illuminates the ceiling.

I think it's also an effect of the inverse-square law.  The ceiling is 
closer to the light source, so it gets a lot more light.  A little tuning
of the light intensity combined with fading might make a huge difference.

-- 
plane{-z,-3normal{crackle scale.2#local a=5;#while(a)warp{repeat x flip x}rotate
z*60#local a=a-1;#end translate-9*x}pigment{rgb 1}}light_source{-9red 1rotate 60
*z}light_source{-9rgb y rotate-z*60}light_source{9-z*18rgb z}text{ttf"arial.ttf"
"RP".01,0translate-<.6,.4,.02>pigment{bozo}}light_source{-z*3rgb-.2}//Ron Parker

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"Timothy R. Cook" wrote:
> 
> Something which troubles me is that when I put a light source near
> a surface (such as a ceiling), the rest of the room is illuminated
> but the surface proximal to the light remains unlit, even when I
> turn on radiosity.

This is more or less realistic. If you have a room with a ceiling light,
try it; the ceiling should be noticibly darker than the walls near the
corners. To get "proper" illumination on the ceiling, use a recursion
limit of 2 or 3 in your radiosity (more than that gives very little benefit).

If you're still not happy with the results, consider playing with your
textures a bit, or using Photoshop (or something similar) to tweak the histo.

-Xplo

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Xplo Eristotle wrote:
> To get "proper" illumination on the ceiling, use a recursion
> limit of 2 or 3 in your radiosity (more than that gives very
> little benefit).

Messing with the radiosity settings looks like it helps.

-- 
Tim Cook
http://empyrean.scifi-fantasy.com

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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