POV-Ray : Newsgroups : povray.bugreports : invalid handling of funky Image-Ratio Server Time: 18 Jan 2019 01:39:16 GMT
  invalid handling of funky Image-Ratio (Message 1 to 8 of 8)  
From: Q0X
Subject: invalid handling of funky Image-Ratio
Date: 23 Dec 2018 19:25:00
Message: <web.5c1fe07ce5c731d84da981590@news.povray.org>
My intention was actually to render a full HD image with the assumption that it
scales the height respectively

invocation with

povray +W1920 +A exp1.pov

scene is

camera {
    location <0, 10, -8>
    look_at  <0, 0,  0>

    right x*1.0/1.0
  }


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From: clipka
Subject: Re: invalid handling of funky Image-Ratio
Date: 23 Dec 2018 21:08:28
Message: <5c1ff94c$1@news.povray.org>
Am 23.12.2018 um 20:22 schrieb Q0X:
> My intention was actually to render a full HD image with the assumption that it
> scales the height respectively

Well, what should I say?
That assumption is wrong.

POV-Ray dates back to times when square pixels were far from standard. 
As a consequence, you need to specify both logical width /and/ height. 
If you omit any of the two, POV-Ray will use to the respective default 
for that dimension, rather than compute it from the logical aspect ratio 
specified in the scene file.

So you're not observing a bug there, but merely the - in your case 
unexpected - effects of intentional behaviour.


POV-Ray v3.8 (currently in development) can automatically compute the 
physical aspect ratio from the logical width and height presuming square 
pixels (by having the `right` camera parameter default to 
`x*image_width/image_height`), but not the other way round, due to 
limitations of its (current) internal architecture.

(Besides, even if POV-Ray could deduce logical image height from logical 
image width and physical aspect ratio, you would have to specify that 
physical aspect ratio somewhere. Your camera statement says you want an 
image aspect ratio of 1:1. For full HD (16:9), that would have to be 
`right x*16/9`.)


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From: Q0X
Subject: Re: invalid handling of funky Image-Ratio
Date: 23 Dec 2018 21:45:00
Message: <web.5c200136683b50b4da981590@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 23.12.2018 um 20:22 schrieb Q0X:
> > My intention was actually to render a full HD image with the assumption that it
> > scales the height respectively
>
> Well, what should I say?
> That assumption is wrong.
>
> POV-Ray dates back to times when square pixels were far from standard.
> As a consequence, you need to specify both logical width /and/ height.
> If you omit any of the two, POV-Ray will use to the respective default
> for that dimension, rather than compute it from the logical aspect ratio
> specified in the scene file.
>
> So you're not observing a bug there, but merely the - in your case
> unexpected - effects of intentional behaviour.
>
>
> POV-Ray v3.8 (currently in development) can automatically compute the
> physical aspect ratio from the logical width and height presuming square
> pixels (by having the `right` camera parameter default to
> `x*image_width/image_height`), but not the other way round, due to
> limitations of its (current) internal architecture.
>
> (Besides, even if POV-Ray could deduce logical image height from logical
> image width and physical aspect ratio, you would have to specify that
> physical aspect ratio somewhere. Your camera statement says you want an
> image aspect ratio of 1:1. For full HD (16:9), that would have to be
> `right x*16/9`.)

Right - I forgot to tell that it crashes consistently.
It should at least exit gracefully.


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From: clipka
Subject: Re: invalid handling of funky Image-Ratio
Date: 24 Dec 2018 11:46:54
Message: <5c20c72e$1@news.povray.org>
Am 23.12.2018 um 22:42 schrieb Q0X:

> Right - I forgot to tell that it crashes consistently.
> It should at least exit gracefully.

Well, I'd call that more than just "funky" ;)
What version are you using? (Please be as precise as possible.)


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From: Q0X
Subject: Re: invalid handling of funky Image-Ratio
Date: 24 Dec 2018 22:20:00
Message: <web.5c215a79683b50b4da981590@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 23.12.2018 um 22:42 schrieb Q0X:
>
> > Right - I forgot to tell that it crashes consistently.
> > It should at least exit gracefully.
>
> Well, I'd call that more than just "funky" ;)
> What version are you using? (Please be as precise as possible.)

Persistence of Vision(tm) Ray Tracer Version 3.7.0.4.unofficial (g++ 7 @
 x86_64-pc-linux-gnu)
This is an unofficial version compiled by:
 Andreas Beckmann <anbe at debian dot org> for Debian <www.debian.org>
 The POV-Ray Team is not responsible for supporting this version.


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From: jr
Subject: Re: invalid handling of funky Image-Ratio
Date: 24 Dec 2018 22:40:00
Message: <web.5c215fbb683b50b48892b50@news.povray.org>
"Q0X" <nomail@nomail> wrote:
> > > invocation with

> > > povray +W1920 +A exp1.pov

> > > scene is

> > > camera {
> > >     location <0, 10, -8>
> > >     look_at  <0, 0,  0>
> > >     right x*1.0/1.0
> > >   }

> clipka <ano### [at] anonymousorg> wrote:
> > Am 23.12.2018 um 22:42 schrieb Q0X:
> >
> > > Right - I forgot to tell that it crashes consistently.
> > > It should at least exit gracefully.
> >
> > Well, I'd call that more than just "funky" ;)
> > What version are you using? (Please be as precise as possible.)
>
> Persistence of Vision(tm) Ray Tracer Version 3.7.0.4.unofficial (g++ 7 @
>  x86_64-pc-linux-gnu)
> This is an unofficial version compiled by:
>  Andreas Beckmann <anbe at debian dot org> for Debian <www.debian.org>
>  The POV-Ray Team is not responsible for supporting this version.

in case it matters, the above "scene", cut + pasted, with the same command-line,
runs fine (just warnings) with 3.7.0.8.unofficial on x86_64-slackware-linux-gnu.


regards, jr.


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From: jr
Subject: Re: invalid handling of funky Image-Ratio
Date: 24 Dec 2018 23:10:00
Message: <web.5c21670a683b50b48892b50@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> "Q0X" <nomail@nomail> wrote:
> > > > invocation with
>
> > > > povray +W1920 +A exp1.pov
>
> > > > scene is
>
> > > > camera {
> > > >     location <0, 10, -8>
> > > >     look_at  <0, 0,  0>
> > > >     right x*1.0/1.0
> > > >   }
>
> > clipka <ano### [at] anonymousorg> wrote:
> > > Am 23.12.2018 um 22:42 schrieb Q0X:
> > >
> > > > Right - I forgot to tell that it crashes consistently.
> > > > It should at least exit gracefully.
> > >
> > > Well, I'd call that more than just "funky" ;)
> > > What version are you using? (Please be as precise as possible.)
> >
> > Persistence of Vision(tm) Ray Tracer Version 3.7.0.4.unofficial (g++ 7 @
> >  x86_64-pc-linux-gnu)
> > This is an unofficial version compiled by:
> >  Andreas Beckmann <anbe at debian dot org> for Debian <www.debian.org>
> >  The POV-Ray Team is not responsible for supporting this version.
>
> in case it matters, the above "scene", cut + pasted, with the same command-line,
> runs fine (just warnings) with 3.7.0.8.unofficial on x86_64-slackware-linux-gnu.

heh, cheated and got found out.  :-)  I did render with +w400 -- the only
change, and things appeared fine.  but checking the output image size, it's
400x600.  so I tried again, this time with +w1920, and now 3.7.0.8 too crashes:

[xcb] Unknown request in queue while dequeuing
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been
called
[xcb] Aborting, sorry about that.
povray-3.7.0.8: xcb_io.c:165: dequeue_pending_request: Assertion
`!xcb_xlib_unknown_req_in_deq' failed.
Aborted


regards, jr.


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From: clipka
Subject: Re: invalid handling of funky Image-Ratio
Date: 25 Dec 2018 01:25:04
Message: <5c2186f0$1@news.povray.org>
Am 24.12.2018 um 23:15 schrieb Q0X:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 23.12.2018 um 22:42 schrieb Q0X:
>>
>>> Right - I forgot to tell that it crashes consistently.
>>> It should at least exit gracefully.
>>
>> Well, I'd call that more than just "funky" ;)
>> What version are you using? (Please be as precise as possible.)
> 
> Persistence of Vision(tm) Ray Tracer Version 3.7.0.4.unofficial (g++ 7 @
>   x86_64-pc-linux-gnu)
> This is an unofficial version compiled by:
>   Andreas Beckmann <anbe at debian dot org> for Debian <www.debian.org>
>   The POV-Ray Team is not responsible for supporting this version.

I can't reproduce the exact issue, but I have reason to believe that it 
has already been fixed in the current v3.8.0-alpha versions.


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