I've had this before and faked it. The attached file has the only light
source at +Z and a camera at -Z. I can see the unilluminated side of the
sphere. Note all sources of reflections are commented out. 

-- 
Always go through life a little bit hungry. 
You never know when you might meet something edible.
	-- The Iron Webmaster, 139

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In article <3A01DBB1.F6A1469D@ij.net>, Matt Giwer <jul### [at] ijnet> 
wrote:

> 	I've had this before and faked it. The attached file has the only light
> source at +Z and a camera at -Z. I can see the unilluminated side of the
> sphere. Note all sources of reflections are commented out. 

Your indentation style is horrible. :-)
Also, "scale 1" doesn't do anything. And you use an image map...I 
replaced it with "wrinkles color_map {[0 rgb 0][1 rgb 1]}" so I could 
render the file.
I assume the problem is that you don't want to see the dark side of the 
sphere? Give the sphere an ambient of 0. It is currently at 0.5, which 
means the minimum illumination will be 0.5. You could also specify 
ambient_light 0 in global_settings, this sets the ambient value of 
everything in the scene to 0.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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> finish {ambient .5}

Can't render it as you have it lacking the image map, but perhaps this is the
problem?

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Chris Huff wrote:
> 
> In article <3A01DBB1.F6A1469D@ij.net>, Matt Giwer <jul### [at] ijnet>
> wrote:
> 
> >       I've had this before and faked it. The attached file has the only light
> > source at +Z and a camera at -Z. I can see the unilluminated side of the
> > sphere. Note all sources of reflections are commented out.
> 
> Your indentation style is horrible. :-)
> Also, "scale 1" doesn't do anything.

	Guilty as charged. Noodling around trying to correctly solve this
problem correctly. 

> And you use an image map...I
> replaced it with "wrinkles color_map {[0 rgb 0][1 rgb 1]}" so I could
> render the file.

> I assume the problem is that you don't want to see the dark side of the
> sphere? Give the sphere an ambient of 0. It is currently at 0.5, which
> means the minimum illumination will be 0.5. You could also specify
> ambient_light 0 in global_settings, this sets the ambient value of
> everything in the scene to 0.

	Playing with ambient is one of the ways of faking it. If there is no
illumination, why should anything be visible regardless of the ambient?
I just want things to behave according to the scene description. 

	I have this image of the light reflecting off of the camera ...:)

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MikeH wrote:
> 
> > finish {ambient .5}
> 
> Can't render it as you have it lacking the image map, but perhaps this is the
> problem?

	Stick in any image you have laying around. Put in a texture. 

	How is it possible to see what is not illuminated?

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"Matt Giwer" <jul### [at] ijnet> wrote in message
news:3A0### [at] ijnet...


> illumination, why should anything be visible regardless of the ambient?

... but that's the whole point of ambient. Its primary use is as a fake
radiosity - giving objects a visible colour when otherwise they would be in
pure shadow.

Time to rtfm?

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In article <3A0### [at] ijnet>, Matt Giwer <jul### [at] ijnet> wrote:

> 	Playing with ambient is one of the ways of faking it. If there is no
> illumination, why should anything be visible regardless of the ambient?

But there *is* illumination. You specified a 50% gray ambient lighting.
Think of it this way: there is a global ambient light source which 
defaults to white. It has no direction or location, so it illuminates 
the scene evenly, is not shadowed or shaded. The color of this light is 
specified by the "ambient_light" keyword in global_settings. Textures 
have an "ambient" component which specifies how much they are affected 
by this ambient light, the two colors are multiplied together and the 
result added to the illumination. The ambient_light keyword gives you a 
way to globally change the ambient values, and the ambient finish 
attribute allows you to control it on a per-texture basis.
Since the default is "ambient_light rgb < 1, 1, 1>", and you specified 
ambient 0.5(which is the same as "ambient rgb < 0.5, 0.5, 0.5>"), what 
you did is tell POV to add rgb < 0.5, 0.5, 0.5> to the illumination of 
each point on the sphere.

Actually, the "ambient_light" keyword isn't even necessary, you can do 
something like this:
#declare AmbLgt = color rgb < 1, 1, 1>;
...
texture {
    ...
    finish {
        ambient AmbLgt*0.5

However, variables may not have existed when ambient_light was added.


> I just want things to behave according to the scene description. 

It is, I assure you. :-)


> 	I have this image of the light reflecting off of the camera ...:)

More like a fill light at the camera position that doesn't leave shadows 
and isn't affected by the contours of the surfaces(no shading). Ambient 
is actually intended as a quick-and-dirty way to simulate diffuse 
illumination, light bouncing off of other objects, but radiosity does a 
much better job of that. Since ambient light can be specified per-object 
and is added to the ordinary illumination, it is often used to make 
glowing objects.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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Tom Melly wrote:

> Time to rtfm?

I think so...

--
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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Tom Melly wrote:
> 
> "Matt Giwer" <jul### [at] ijnet> wrote in message
> news:3A0### [at] ijnet...
> 
> > illumination, why should anything be visible regardless of the ambient?
> 
> ... but that's the whole point of ambient. Its primary use is as a fake
> radiosity - giving objects a visible colour when otherwise they would be in
> pure shadow.
> 
> Time to rtfm?

	Oh. Guess so. 

	It has always worked as though it were the purpose to make it seen
without a particular finish. Why read when it worked exactly as
expected? No excuse, Sir! 

-- 
Here is the rule and read it clear, only the US government can 
invoke god and no one else can. 
	-- The Iron Webmaster, 167

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Chris Huff wrote:

> Your indentation style is horrible. :-)

Thats the Allman style
try an even worse style - Whitesmiths
or the tuxracer src for some v bad indentation
personally I like the K&R style

see  http://www.tuxedo.org/~esr/jargon/html/entry/indent-style.html for more.

Bye
Pabs

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I follow the rule of finish{ambient 0} and it looks very dark to dull.
To make it look halfway like the original image I have to go the
light_source as  rgb<1,1,1>*3 and *5 isn't that bad. 

	OK, I am still missing something as that should not be necessary,
right? 

	And if it is necessary, what am I missing regarding the consistant
nature of the scene language? Was ambient originally a hack? 

	Attachment indented for the purist at heart. This is a side view that
will give essentially the effect I desire. 

	BTW: congrats, I guess, to the developer of the type 1 mapping for
first converting the image to a square or whatever the trick was to
avoid the need for scaling a rectangular image to a sphere. 

	And if you do not have a picture of the earth around to see the effect
it is simply the earth with a light and dark side and the shaded
transition from light to dark. Just stick in any image and look at the
lit hemisphere with *3 compared to *5 and see it is clearly less of half
than it should be. 

-- 
If there is anything that makes life complicated it is
trying to find decisions other than pragmatic. We appeal
to gods to make life hard. 
	-- The Iron Webmaster, 222

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Matt Giwer wrote:
> 
> If there is no
> illumination, why should anything be visible regardless of the ambient?
> I just want things to behave according to the scene description.

They *do* behave according to the scene description.

Ambient *is* illumination. It's directly added to whatever object(s) you
tell it to affect. In this case, since you've set the ambient of the
sphere to .5, the entire sphere is being illuminated by a constant,
directionless gray light. As someone else has mentioned, you could think
of it as "glowing".

If you were to shine a point light on this sphere, then every point on
the sphere would receive its normal illumination from the light, PLUS an
additional .5 from the ambient lighting.

This is one of the simplest concepts in POV-Ray, IMO. What part of it
*don't* you get?

-Xplo

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Matt Giwer wrote:
> 
>         I follow the rule of finish{ambient 0} and it looks very dark to dull.
> To make it look halfway like the original image I have to go the
> light_source as  rgb<1,1,1>*3 and *5 isn't that bad.

Try setting the sphere's diffuse to 1 (the default is .6, for some reason).

-Xplo

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In article <3A020F47.B09AA20D@hotmail.com>, Pabs <pab### [at] hotmailcom> 
wrote:

> Thats the Allman style
> try an even worse style - Whitesmiths
> or the tuxracer src for some v bad indentation
> personally I like the K&R style

It looks like an Allman/K&R mix, but it has a bunch of spaces where they 
shouldn't be, and some spots are missing spaces. But what I was really 
referring to was the sphere at the end.

I tend to use a modified K&R style for POV code, and Allman style with 
4-space indents for C/C++/ObjC. The K&R style lets me fit more POV 
objects and code into view, which makes it easier to edit the scene, but 
I find it easier to read C/C++/ObjC in Allman style.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-12F744.10000703112000@news.povray.org...
>
> > Thats the Allman style
> > try an even worse style - Whitesmiths
> > or the tuxracer src for some v bad indentation
> > personally I like the K&R style
>

Never had much time for the Altmans or Whitesnake myself, but R&B is cool.

BTW Shouldn't this be in O.T.?

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In article <3A0### [at] unforgettablecom>, 
inq### [at] unforgettablecom wrote:

> Try setting the sphere's diffuse to 1 (the default is .6, for some 
> reason).

The reason is that the ambient value is not 0 by default(I think the 
default for ambient is 0.2), and scenes often have multiple light 
sources. If it was 1 by default, everything would be washed out unless 
you set your own value.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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Xplo Eristotle wrote:
> 
> Matt Giwer wrote:
> >
> >         I follow the rule of finish{ambient 0} and it looks very dark to dull.
> > To make it look halfway like the original image I have to go the
> > light_source as  rgb<1,1,1>*3 and *5 isn't that bad.
> 
> Try setting the sphere's diffuse to 1 (the default is .6, for some reason).

	Increasing diffuse to 3 helps greatly. 

-- 
Wilkomorski is a frigging liar but holohuggers 
love him. 
	-- The Iron Webmaster, 173

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Matt Giwer wrote:
> 
> Xplo Eristotle wrote:
> >
> > Matt Giwer wrote:
> > >
> > >         I follow the rule of finish{ambient 0} and it looks very dark to dull.
> > > To make it look halfway like the original image I have to go the
> > > light_source as  rgb<1,1,1>*3 and *5 isn't that bad.
> >
> > Try setting the sphere's diffuse to 1 (the default is .6, for some reason).
> 
>         Increasing diffuse to 3 helps greatly.

An rgb 1 light that hits an rgb 1 surface with a diffuse of 1 and an
ambient of 0 should produce pure white. The fact that you need to
"overcharge" the lighting simulation suggests to me that you're using
light fading, shining the light through a partially transparent object
or absorbing media, or using a very dark image as a texture. I can see
from the code that the first two aren't the case, so I suspect it's the
third one.

-Xplo

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Xplo Eristotle wrote:

> If you were to shine a point light on this sphere, then every point on
> the sphere would receive its normal illumination from the light, PLUS an
> additional .5 from the ambient lighting.
> 
> This is one of the simplest concepts in POV-Ray, IMO. What part of it
> *don't* you get?

	Because when I have used it other times it has always appeared to work
as though it were simply reflecting more of the illumination so there
was never a reason to Read The Fine Docs. 

-- 
Live fast, love well, and have a glorious website.
<a href="http://www.giwersworld.org/mgiwer/">
The rest of Matt Giwer's World</a>
	-- The Iron Webmaster, 61

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Xplo Eristotle wrote:
> 
> Matt Giwer wrote:
> >
> > Xplo Eristotle wrote:
> > >
> > > Matt Giwer wrote:
> > > >
> > > >         I follow the rule of finish{ambient 0} and it looks very dark to dull.
> > > > To make it look halfway like the original image I have to go the
> > > > light_source as  rgb<1,1,1>*3 and *5 isn't that bad.
> > >
> > > Try setting the sphere's diffuse to 1 (the default is .6, for some reason).
> >
> >         Increasing diffuse to 3 helps greatly.
> 
> An rgb 1 light that hits an rgb 1 surface with a diffuse of 1 and an
> ambient of 0 should produce pure white. The fact that you need to
> "overcharge" the lighting simulation suggests to me that you're using
> light fading, shining the light through a partially transparent object
> or absorbing media, or using a very dark image as a texture. I can see
> from the code that the first two aren't the case, so I suspect it's the
> third one.

	In POV binaries I am posting the results of diffuse 1 2 and 3 in Sub:
pov.general ambient v diffuse

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