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From: Xplo Eristotle
Subject: Inexplicable shadow?
Date: 18 Nov 1999 16:15:00
Message: <38346C9A.20CB7D73@unforgettable.com>
I tried this in the newusers group, but got one response from someone
who couldn't reproduce the effect, so...

The following brief scene:

camera
        {
        location  <0,6,-10>
        look_at   <0,5,0>
        }
        
light_source
        {
        <-350,1000,-250>
        color rgb <2,2,1.8>
        }
        
prism
        {
        conic_sweep
        linear_spline
        .5,1,5
        <4,8>,<-4,8>,<-4,-8>,<4,-8><4,8>
        rotate <180,0,0>
        translate <0,1,0>
        scale <1,32,1>
        translate <0,-11.5,5>
        pigment { color rgb <.5,.5,.5> }
        }

...is supposed to produce a tall, narrow, medium-gray truncated
pyramidal shape. It does in fact do this, but what has me confused is
the narrow dark band that appears on the left side of the front face. It
looks like a shadow, but there's nothing to cast one.

Any ideas?

-- 
Xplo Eristotle
http://start.at/xplosion/


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From: Bill DeWitt
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 16:22:45
Message: <38346e25@news.povray.org>
Xplo Eristotle <inq### [at] unforgettablecom> wrote in message
news:38346C9A.20CB7D73@unforgettable.com...
> I tried this in the newusers group, but got one response from someone
> who couldn't reproduce the effect, so...
>
>
> ...is supposed to produce a tall, narrow, medium-gray truncated
> pyramidal shape. It does in fact do this, but what has me confused is
> the narrow dark band that appears on the left side of the front face. It
> looks like a shadow, but there's nothing to cast one.
>
> Any ideas?
>

    How many colors is your screen resolution set for?


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From: Ken
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 17:13:49
Message: <383479DE.E16AF8F2@pacbell.net>
Xplo Eristotle wrote:
> 
> I tried this in the newusers group, but got one response from someone
> who couldn't reproduce the effect, so...

> ...is supposed to produce a tall, narrow, medium-gray truncated
> pyramidal shape. It does in fact do this, but what has me confused is
> the narrow dark band that appears on the left side of the front face. It
> looks like a shadow, but there's nothing to cast one.
> 
> Any ideas?

  I am entirely unable to reproduce the problem that you describe.
I rendered it at both high and low resolutions, added a high ambient
to a finish statement, removed the diffuse value, tried it with and
without antialiasing, and changed the camera position a few times.
Regardless I have been unsuccesful in finding fault with your object.

If possible could you render the object and in a paint program place
an arrow at the fault then post a small image of the problem in the
images group ?

Tell us what version of the program you are using, what platform, and
the color resolution your system is operating on. As Bill mentioned
if you are using your system with anything less the millions of
colors at a 24 bit resolution you might be seeing color banding which
most of us will not be able to reproduce at higher resolution levels.

-- 
Ken Tyler -  1200+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/


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From: Xplo Eristotle
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 17:51:11
Message: <38348339.F7442DE6@unforgettable.com>
Ken wrote:
> 
> Xplo Eristotle wrote:
> >
> > I tried this in the newusers group, but got one response from someone
> > who couldn't reproduce the effect, so...
> 
> > ...is supposed to produce a tall, narrow, medium-gray truncated
> > pyramidal shape. It does in fact do this, but what has me confused is
> > the narrow dark band that appears on the left side of the front face. It
> > looks like a shadow, but there's nothing to cast one.
> >
> > Any ideas?
> 
>   I am entirely unable to reproduce the problem that you describe.
> I rendered it at both high and low resolutions, added a high ambient
> to a finish statement, removed the diffuse value, tried it with and
> without antialiasing, and changed the camera position a few times.
> Regardless I have been unsuccesful in finding fault with your object.
> 
> If possible could you render the object and in a paint program place
> an arrow at the fault then post a small image of the problem in the
> images group ?

Okay. At the moment, there is just such an image on the web...

http://members2.easyspace.com/durendal/altar.jpg

...but I can post it to the images NG as well.

(The image at that URL has sky and sea and stuff in it, but I've tried
it with the extremely simple code posted here and the problem still
appears, so I'm convinced that it's independent of the additional detail.)

> Tell us what version of the program you are using, what platform, and
> the color resolution your system is operating on. As Bill mentioned
> if you are using your system with anything less the millions of
> colors at a 24 bit resolution you might be seeing color banding which
> most of us will not be able to reproduce at higher resolution levels.

The latest version publicly available.. 3.1g or thereabouts. 7100/66AV
w/Sonnet G3/266 upgrade running MacOS 8.6. 640 x 480 x 24-bit display.

I call the band "narrow", but in fact it's fairly large (as you'll see),
and couldn't possibly be the result of color banding.

-- 
Xplo Eristotle
http://start.at/xplosion/


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From: Ken
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 18:03:27
Message: <38348582.1F3F44BC@pacbell.net>
Xplo Eristotle wrote:

> > If possible could you render the object and in a paint program place
> > an arrow at the fault then post a small image of the problem in the
> > images group ?
> 
> Okay. At the moment, there is just such an image on the web...
> 
> http://members2.easyspace.com/durendal/altar.jpg
> 
> ...but I can post it to the images NG as well.

No need that was enough :)
 

> > Tell us what version of the program you are using, what platform, and
> > the color resolution your system is operating on. As Bill mentioned
> > if you are using your system with anything less the millions of
> > colors at a 24 bit resolution you might be seeing color banding which
> > most of us will not be able to reproduce at higher resolution levels.
> 
> The latest version publicly available.. 3.1g or thereabouts. 7100/66AV
> w/Sonnet G3/266 upgrade running MacOS 8.6. 640 x 480 x 24-bit display.
> 
> I call the band "narrow", but in fact it's fairly large (as you'll see),
> and couldn't possibly be the result of color banding.

That is an impressive defect and one I am not seeing on the windows version
of the program. I suspect it might be a precision problem with the Mac
version but I have no way to confirm this. Maybe we can get another Mac
user to try your example and see it they can reproduce it. Otherwise
I have no idea what may be causing it.

Sorry for the lack of help :(

-- 
Ken Tyler -  1200+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/


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From: Chris Huff
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 18:43:19
Message: <38348FC6.BE44D52@compuserve.com>
It occurs in POV-Ray PPC Mac version 3.1g.r1, but does not occur in the
latest release of POV-RayUnofficial.
It also doesn't occur in the Mac version of the Superpatch which I did,
I haven't compiled the version done by Thorsten Froehlich yet. The
version I did was based on the MS-DOS Superpatch source.
You are probably right, it looks like a precision thing.


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From: Ken
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 18:53:26
Message: <3834913C.494C723@pacbell.net>
Chris Huff wrote:
> 
> It occurs in POV-Ray PPC Mac version 3.1g.r1, but does not occur in the
> latest release of POV-RayUnofficial.

> You are probably right, it looks like a precision thing.

Or a compiler specific problem. Does everyone use CodeWarrior to compile
Mac programs or are there others available ?

-- 
Ken Tyler -  1200+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/


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From: Chris Huff
Subject: Re: Inexplicable shadow?
Date: 18 Nov 1999 19:10:26
Message: <38349625.6E475A83@compuserve.com>
>Or a compiler specific problem.<
I used CodeWarrior to compile my versions, and POV-RayUnofficial is also
compiled with CodeWarrior, as is the official version. So it probably
isn't CodeWarrior. :-)


>Does everyone use CodeWarrior to compile Mac programs or are there
others available ?<

Probably most Mac programmers who have the money use CodeWarrior, but it
is an expensive development environment. I was able to get it for $99
because I am a student, but the non-academic edition costs a lot
more.(There is also a ~$70 "Discover Programming" version. I am not sure
what the full, non-academic version costs, you could check the web
site.)

There is also Apple's MPW(Macintosh Programmers Workshop) which is free
for download(and included with CodeWarrior). MPW is probably the most
versatile, but CodeWarrior is easier to use.(MPW has a UNIX-like
interface and uses makefiles, CodeWarrior uses "projects")

There may be some people still using "ThinkC"(or something similar,
can't remember the exact name). I think it was Symantec who made this,
it was dropped a while ago and is quite out of date.
There are probably quite a few others, but I don't know of any.


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From: Chris Huff
Subject: Re: Inexplicable shadow?
Date: 19 Nov 1999 14:36:59
Message: <3835A790.A5D2D840@compuserve.com>
Even stranger, it doesn't occur in my compile of the official
version(POV-Ray PPC Mac version 3.1g.r1).
This should be exactly the same as the official compile, but the problem
seems to show itself only in the officially distributed version.


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From: Xplo Eristotle
Subject: Re: Inexplicable shadow?
Date: 19 Nov 1999 14:50:08
Message: <3835AA4F.FA17C1C8@unforgettable.com>
Chris Huff wrote:
> 
> Even stranger, it doesn't occur in my compile of the official
> version(POV-Ray PPC Mac version 3.1g.r1).
> This should be exactly the same as the official compile, but the problem
> seems to show itself only in the officially distributed version.

That's weird.. but at least there's a workaround. Thanks guys. :)

-- 
Xplo Eristotle
http://start.at/xplosion/


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