POV-Ray : Newsgroups : povray.binaries.misc : Strange behaviour Server Time: 19 Dec 2018 14:14:31 GMT
  Strange behaviour (Message 1 to 4 of 4)  
From: SomeOne
Subject: Strange behaviour
Date: 20 Jun 2004 08:15:38
Message: <40d547aa@news.povray.org>
Hi,

I'm a bit new to POV so maybe I'm asking an obvious question. I stumbled across
this problem that I can't figure out.

I have this scene:

#include "colors.inc"

global_settings { assumed_gamma .5 }

camera {
    location <0, 4, -6>
    look_at  <0, 0,  0>
}


plane {
    < 0, 1, 0 >, 0
    pigment {
     checker
     color Red, color Blue
    }
}


light_source { <5, 3, -40>, color White}

which produces this image: <test1.png>

Then I change the orientation of the plane from <0,1,0> to <0.2,1,0> and this
is the result: <test2.png>

If I change the orientation even further to <1,1,0> it gets even worse:
<test3.png>

I'm using WIndows XP (Home) with POV-Ray 3.6.0.icl8.win32

Can anyone explain what causes the shrinking/disappearance of (some of) the
tile rows and how to overcome this?

-- 
SomeOne


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Attachments:
Download 'test1.png' (43 KB)
Download 'test2.png' (78 KB)
Download 'test3.png' (104 KB)

Preview of image 'test1.png'
test1.png

Preview of image 'test2.png'
test2.png

Preview of image 'test3.png'
test3.png


 

From: William Pokorny
Subject: Re: Strange behaviour
Date: 20 Jun 2004 12:40:01
Message: <40d585a1$4@news.povray.org>
Think of the checker pattern as being fixed in 3d space - an infinite stack
of colored cubes - while you cut this space with the plane. The differences
in the images you see are an artifact of how the plane cuts through the
stack of colored cubes. You could rotate the pattern to match or the more
usual method would be to apply the pattern to the plane in say the xy plane
and then rotate or translate both as one entity or object in your scene.

An aside:  The more normal way to post you inquery would have been to post
the images and question to povray.images.binaries. This group is, I gather,
for oddball binary postings and it is not as closely followed as some
groups.

"SomeOne" <ask### [at] yahoocouknospam> wrote in message
news:40d547aa@news.povray.org...
> Hi,
>
> I'm a bit new to POV so maybe I'm asking an obvious question. I stumbled
across
> this problem that I can't figure out.
>


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From: Kenneth
Subject: Re: Strange behaviour
Date: 7 Feb 2006 11:10:01
Message: <web.43e87fa46e1607594e7d119a0@news.povray.org>
Hi!

Just wanted to echo the previous comment about this "Misc" news thread being
a not-too-often-visited place for a lot of users.  (I myself practically
never come here; I just happened to click on it out of boredom! ;-)

I also thought I'd comment on your assumed_gamma of .5 usage, to hopefully
give some useful advice. That particular value seems odd to me (and I'm
known for "abusing" assumed_gamma myself.) The POV docs --and lots of other
users--recommended 1.0, although personally, I use 1.8 or 2.2, depending on
which computer I'm running POV on. They just "look" better to me. (This is
a big, thorny topic, as I'm sure you'll become aware of, the more you use
POV-Ray and the more news posts you read.) But I haven't run across the use
of .5 until your scene.  A typical scene run that way would probably look
unnaturally "washed out," although your checkered plane may not show that.
My advice would be to do some experiments using different values, and see
what they do.

Ken Walker


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From: SmartDen
Subject: Re: Strange behaviour
Date: 15 Sep 2006 11:10:00
Message: <web.450a89886e16075978e8d7530@news.povray.org>
"SomeOne" <ask### [at] yahoocouknospam> wrote:
> Hi,
>
> I'm a bit new to POV so maybe I'm asking an obvious question. I stumbled across
> this problem that I can't figure out.
>
> I have this scene:
>
> #include "colors.inc"
>
> global_settings { assumed_gamma .5 }
>
> camera {
>     location <0, 4, -6>
>     look_at  <0, 0,  0>
> }
>
>
> plane {
>     < 0, 1, 0 >, 0
>     pigment {
>      checker
>      color Red, color Blue
>     }
> }
>
>
> light_source { <5, 3, -40>, color White}
>
> which produces this image: <test1.png>
>
> Then I change the orientation of the plane from <0,1,0> to <0.2,1,0> and this
> is the result: <test2.png>
>
> If I change the orientation even further to <1,1,0> it gets even worse:
> <test3.png>

I solved this problem with:
pigment {
....
rotate <0,0,45>
}

>
> I'm using WIndows XP (Home) with POV-Ray 3.6.0.icl8.win32
>
> Can anyone explain what causes the shrinking/disappearance of (some of) the
> tile rows and how to overcome this?
>
> --
> SomeOne


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