I think I've discovered a bug in POV-Ray 3.1g. When the camera looks through
three or more "panes" of transparent material, the panes farthest away will
be coloured in completely black. It's hard to describe, so here is a simple
scene that causes the problem. In case it's relevant, my processor is an AMD
900 and I am running Windows 98.

//////////////////////////////////////////////
background {rgb <1,1,1>}

#declare Transparent =
pigment {rgbt <1,1,1,0.9>}

#declare Sheet =
box {<-1,-1,-0.05>,<1,1,0.05> pigment {Transparent}}


object {Sheet}
object {Sheet translate z*2}
object {Sheet translate z*4}

camera {location <2.1,0,-7> look_at <0,0,5>}
light_source {<10,10,-10> color 1}
////////////////////////////////////////////

Has anyone encountered this problem before? Is there a workaround?

Thanks in advance,
Bryan Spitz

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Bryan Spitz wrote:
> 
> I think I've discovered a bug in POV-Ray 3.1g. When the camera looks through
> three or more "panes" of transparent material, the panes farthest away will
> be coloured in completely black. It's hard to describe, so here is a simple
> scene that causes the problem. In case it's relevant, my processor is an AMD
> 900 and I am running Windows 98.
> 
> [...]

No bug, it's a well known and quite reasonable behaviour.  Use
max_trace_level in global_settings to influence this.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

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Add:

global_settings  {  max_trace_level 10  }

=Bob=


"Bryan Spitz" <bry### [at] yahoocom> wrote in message
news:3ab26393$1@news.povray.org...
: I think I've discovered a bug in POV-Ray 3.1g. When the camera looks
through
: three or more "panes" of transparent material, the panes farthest away
will
: be coloured in completely black. It's hard to describe, so here is a
simple
: scene that causes the problem. In case it's relevant, my processor is an
AMD
: 900 and I am running Windows 98.
:
: //////////////////////////////////////////////
: background {rgb <1,1,1>}
:
: #declare Transparent =
: pigment {rgbt <1,1,1,0.9>}
:
: #declare Sheet =
: box {<-1,-1,-0.05>,<1,1,0.05> pigment {Transparent}}
:
:
: object {Sheet}
: object {Sheet translate z*2}
: object {Sheet translate z*4}
:
: camera {location <2.1,0,-7> look_at <0,0,5>}
: light_source {<10,10,-10> color 1}
: ////////////////////////////////////////////
:
: Has anyone encountered this problem before? Is there a workaround?
:
: Thanks in advance,
: Bryan Spitz
:
:

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On Fri, 16 Mar 2001 14:03:24 -0500 Bryan Spitz wrote:

>I think I've discovered a bug in POV-Ray 3.1g. When the camera looks through
>three or more "panes" of transparent material, the panes farthest away will
>be coloured in completely black.

  Hi, Bryan. Here's an excerpt from the POV-Ray v3.1 docs, section 4.10.6

"The other symptom you could see is with transparent objects. For instance,
try making a union of concentric spheres with a clear texture on them. Make
ten of them in the union with radius's from 1 to 10 and render the scene.
The image will show the first few spheres correctly, then black. This is
because a new level is used every time you pass through a transparent
surface. Raise max_trace_level to fix this problem."

  There are cases in which you might want to raise max_trace_level up to a
certain point and not beyond it. Use the lowest setting that will give
acceptable results in the final image - higher settings may take longer to
render.

-- 
Alan - ako### [at] povrayorg - a k o n g <at> p o v r a y <dot> o r g
http://www.povray.org - Home of the Persistence of Vision Ray Tracer

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Bryan Spitz wrote:
> 
> I think I've discovered a bug in POV-Ray 3.1g.
[snip]

Hi Bryan,
In addition to what others have said, I suggest you take a look at the POV-Ray
VFAQ (Very Frequently Asked Questions):
http://www.students.tut.fi/~warp/povVFAQ/

and in particular the section concerning max_trace_level:
http://www.students.tut.fi/~warp/povVFAQ/languageVFAQ.html#maxtracelevel

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt

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