"Jim Charter" <jrc### [at] aolcom> wrote in message:
> You did better than me, I'll be darned if I could find the manual.
 Thanks :-)

> With POV-Ray, instead of a canned effect, such as sunlight, being
> readily available, there is instead a devoted community endlessly
> experimenting with newer and better ways to obtain such effects.
> POV-Ray lends itself to the spirit of investigation and experimentation.
>   You can monitor this spirit on the POV newsgroups.  Ultimately, this
> leads to greater originality and scope in the artwork produced.  After
> woorking with POV for four years I still find that experts on the server
> are working with effects whose refinement I can barely perceive, let
> alone understand and accomplish myself.

I agree.

> So that got a bit longwinded but in summary, if your interest is
> freeware, and basically amateur in its goals, I would recommend POV over
> Virtualight unreservedly. You will become very skilled indeed before you
> "outgrow" it, and the community of other users is a rich resource. But
> the knowledge you gain that can be ported to the commercial world is
> relatively general.  If you are trying to accumulate knowledge toward a
> commercial career, you may need to be more crafty in the software you
> choose to learn.

What modeler would you recommend for POVRay?  I strived to do everything
using a text editor as I reckon I will have better control over the scene
but is it really feasible to come up with higly complex scene without the
help of a modeler.

Daniel.

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"Hugo Asm" <hua### [at] post3teledk> wrote:
> I think it just means the skydome does not cast a big shadow over the
entire
> world. In POV-Ray it's called a "sky sphere" and it probably works the
same
> way when you activate radiosity. Here's a little example; try toggling the
> on/off switches and see the differences:

Thanks for the example.  That did the trick and it looks great too!

Daniel.

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Can anyone comment about global illumination in POVRay?  Thanks.

Daniel.

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> What modeler would you recommend for POVRay?  I strived to do
> everything using a text editor as I reckon I will have better control over
> the scene but is it really feasible to come up with higly complex scene
> without the help of a modeler.

A modeller is handy in many cases. The trouble I've always had with
modellers are their GUI.. Their interface is so cluttered and difficult to
understand and remember. I have only found one exception to this: Wings3D,
and it is freeware. Even if you don't know anything about polygon modelling
(and I didn't) I think you will learn the application quick and easily.

Wings3D is solely a polygon modeller (not like Blender). It can export
meshes for POV-Ray. You will need a fast computer (about 1 Ghz or more)
because it's programmed in a kind of "basic language". This may scare off
some people from downloading it, but I recommend it nevertheless.
www.wings3d.com  And of course you need a 3d accelerated graphicscard.

Regards,
Hugo

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Andreas Kreisig wrote:
> you don't have to spend lots of bucks for a commercial 3D
> application to get good results. But you have to learn to use two
> rather complicated applications, this may be a small disadvantage.

I couldn't stand for this comment.  :o)  Isn't all the commercial
applications complicated as well?  I throw them away the minute I see their
interface. But I'm biased towards scripting anyway, because I started
programming a long time ago. I find POV-Ray to be excellent also for newbies
because you don't actually SEE the possibilities of the program, until you
begin searching for them in the documentation. This helped me, take things
one step at a time.

Commercial applications seems more automated, in some cases, and that can be
a great thing. But I can automate a great deal of things in POV-Ray too.

Regards,
Hugo

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> Can anyone comment about global illumination in POVRay?

Well, the principle is very simple: All objects cast shadows, as you know.
But they also reflect light, when you turn on radiosity. This is the same
term as global illumination. You need it, to obtain a natural spread of
light. The reflections from radiosity are just not mirror-like. They are
diffuse. It's the same effect that happens when light enters from a window.
The walls reflect that light, in very diffuse directions. That's why you
don't see a clear reflection on the wall. Unlike a mirror, it's a diffuse
reflection.

The documentation for POV-Ray is very informative, I hope you'll read it. I
also recommend that you load the include-file "rad_def.inc" into the editor.
All parameters are setup and ready to use. You can choose between different
qualities of radiosity. They are simple to use. You just do as I did, in the
example I posted yesterday... When radiosity is turned on, light will bounce
off all objects, at least once. You can adjust the light to bounce off
twice, or more times if necessary (that is rare).

The sky_sphere is also an object, but unlike most objects, the sky_sphere
emits light. It's not a "light_source" but on the other hand, it doesn't
NEED a "light_source" to ... light.. Perhaps this sounds a bit strange, but
the point is: An object can either absorb light, or emit light. In both
cases, radiosity makes the light travel to nearby objects. Any object can
emit light of course, not just the sky_sphere. To make an object emit light,
you raise the "ambient" value in the object's finish statement. Like this:

sphere { 0, 1 pigment { rgb 1 } finish { ambient 1 } }

If you don't want the object to emit light, set ambient to 0.. Please note
that you can set the ambient value higher than 1 if necessary... Maybe you
ask yourself: If objects can emit light, why have light_sources?  They're
not needed.  That's true, and you can make a beautiful scene without any
light_sources, just with pure radiosity. This would be the most realistic
approch. But in many cases, it's too slow if you want good quality. That's
why we mix radiosity with ordinary light_sources.. These light_sources rely
on a completely other formula, and are independant of radiosity. But they
have some advantages, such as clear defined shadows, and nice specular
highlights on objects.. The trick is then to balance the two formulas
(radiosity and light_source) to get realistic results.

But it's possible... And OH, I have to stop writing now.. I have work to do.

Regards,
Hugo

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"Hugo Asm" <hua### [at] post3teledk> wrote:
> Well, the principle is very simple: All objects cast shadows, as you know.
> But they also reflect light, when you turn on radiosity. This is the same
> term as global illumination...

Thanks Hugo, that's very helpful and does clear up the ambiguities.

Regards,
Daniel.

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Hugo Asm wrote:

> Andreas Kreisig wrote:
>> you don't have to spend lots of bucks for a commercial 3D
>> application to get good results. But you have to learn to use two
>> rather complicated applications, this may be a small disadvantage.
> 
> I couldn't stand for this comment.  :o)  Isn't all the commercial
> applications complicated as well?

Yes of course. What I wanted to point out is that you have to learn *two* 
programs instead of only one when you buy a commercial, expensive and 
allmost full-featured 3d software. I think it's never (and it probably will 
never be) easy to create something in three dimensions.

> I throw them away the minute I see their interface.

To build an interface for such a complex software is allways a compromise 
between usability and design. Some GUIs are better, some are worse.

> But I'm biased towards scripting anyway, because I started programming a 
> long time ago.

This is of course a good supposition to work with SDL.

> I find POV-Ray to be excellent also
> for newbies because you don't actually SEE the possibilities of the
> program,

And you don't actually SEE what you're doing. This kind of abstraction may 
cause problems, at least for me :)

I'm a Linux user for a long time now and a view years ago I had an endless 
discussion with a Linux freak who only use the console for nearly all of 
his work while I rather use a Desktop for my daily work. He even said that 
it's more easy for a secretary to learn Tex (a script based 'word 
processor') than to learn MS Word or something similar. I mentioned that in 
the case that you're using a GRAPHICAL user interface, you have an 
additional 'channel' to learn: visibility. This is a fact, proofed by 
scientists who are dealing with learning theory.

> Commercial applications seems more automated, in some cases, and that can
> be a great thing. But I can automate a great deal of things in POV-Ray
> too.

There are some more reason why I prefer to use a modeler (not necessarily a 
commercial one), but I don't want to start this topic again ...:) Everybody 
should feel free to use what he/she wants.

Regards,
Andreas

-- 
http://www.render-zone.com

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Hugo Asm <hua### [at] post3teledk> wrote:
> radiosity. This is the same term as global illumination.

  It's better to use term "global illumination" (and if you want to be
more specific, add "stochastic" before it) than "radiosity" when writing
to not-only-povray groups to not to cause confusion.
  "Radiosity" is the name of a specific algorithm (which has nothing to do
with the algorithm used by POV-Ray) and the term is usually used in this
meaning.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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"Warp" <war### [at] tagpovrayorg> wrote:
>   It's better to use term "global illumination" (and if you want to be
> more specific, add "stochastic" before it) than "radiosity" when writing
> to not-only-povray groups to not to cause confusion.
>   "Radiosity" is the name of a specific algorithm (which has nothing to do
> with the algorithm used by POV-Ray) and the term is usually used in this
> meaning.

So, to sum it up, radiosity is a subset of global illumination, i.e., one of
the method or algorithm used in global illumination.  The context of
radiosity in POV-Ray means achieving the same effect but not implemented
using that particular "Radiosity" algorithm.  If that is the case, any
reason for the difference in implementation?

Daniel.

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