cyberspittle wrote:
> Hi ______.
> 
> I've mae some animations in 640x480, but want to re-render in HD format. I
> was wondering what custom resolution that is? I searched on the internet
> (Google) but am confused, as there seem to be different resolutions; ie.
> 720p 1080i 1080p. Anyone render to WXGA monitor? I am concerned about
> stretching. Right now, I have a 19" Viewsonic WXGA monitor (cheap, I know,
> but less than $200). It looks fine on the PC, but when I output my display
> on a TV using s-video, it isn't in a wide screen. Is it a resolution
> problem (I am sharing my Win XP desktop)? TIA.

You need to set two things - the image size and aspect ratio.

To set the image size you simply make an entry into your resolution.ini 
file for the appropriate size (720p = 1280x72, 1080i/p = 1920x1080). 
All HDTV compatible equipment should handle all three formats equally 
well, so it's upto you which one you want to use (quality-wise there 
isn't much of a difference as the 1080i/p formats have to make some 
sacrifices to squeeze all that info into each frame).

But pixels in an HDTV image are not square (aspect ratio of 1), so you 
need to tell povray to render non-square pixels.  I'm not sure if there 
is a more efficient way of doing this, but I always use the camera 
command for this.  You simply add the "right" command to the camera, 
with the desired aspect ratio after the "right command.  For HDTV this 
is 16:9;

camera {
   location <0,0,0>
   look_at <0,0,1>
   up y
   right (16/9)
}

Bryan

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Bryan Heit wrote:
> But pixels in an HDTV image are not square (aspect ratio of 1)

Yes they are.*

> , so you
> need to tell povray to render non-square pixels.  I'm not sure if
> there is a more efficient way of doing this, but I always use the
> camera command for this.  You simply add the "right" command to the
> camera, with the desired aspect ratio after the "right command.  For
> HDTV this is 16:9;
>
> camera {
>   location <0,0,0>
>   look_at <0,0,1>
>   up y
>   right (16/9)
> }

This is the right thing to do, yes. But it doesn't create non-square pixels; 
on the contrary it creates square pixels because the set aspect ratio in the 
camera (16/9) matches the aspect ratio of the image (1280x720 or 1920x1080).

* According to Wikipedia, the pixel aspect ratio of native HD signals is a 
"square" 1.0, or 1 pixel length = 1 pixel width. New HD compression and 
recording formats such as HDV use rectangular pixels for more efficient 
compression and to open HDTV acquisition for the consumer market, but I 
think that's irrelevant with regard to rendering.

Rune
-- 
http://runevision.com

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Bryan Heit <bjh### [at] NOSPAMucalgaryca> wrote:
> cyberspittle wrote:
> > Hi ______.
> >
> > I've mae some animations in 640x480, but want to re-render in HD format. I
> > was wondering what custom resolution that is? I searched on the internet
> > (Google) but am confused, as there seem to be different resolutions; ie.
> > 720p 1080i 1080p. Anyone render to WXGA monitor? I am concerned about
> > stretching. Right now, I have a 19" Viewsonic WXGA monitor (cheap, I know,
> > but less than $200). It looks fine on the PC, but when I output my display
> > on a TV using s-video, it isn't in a wide screen. Is it a resolution
> > problem (I am sharing my Win XP desktop)? TIA.
>
> You need to set two things - the image size and aspect ratio.
>
> To set the image size you simply make an entry into your resolution.ini
> file for the appropriate size (720p = 1280x72, 1080i/p = 1920x1080).
> All HDTV compatible equipment should handle all three formats equally
> well, so it's upto you which one you want to use (quality-wise there
> isn't much of a difference as the 1080i/p formats have to make some
> sacrifices to squeeze all that info into each frame).
>
> But pixels in an HDTV image are not square (aspect ratio of 1), so you
> need to tell povray to render non-square pixels.  I'm not sure if there
> is a more efficient way of doing this, but I always use the camera
> command for this.  You simply add the "right" command to the camera,
> with the desired aspect ratio after the "right command.  For HDTV this
> is 16:9;
>
> camera {
>    location <0,0,0>
>    look_at <0,0,1>
>    up y
>    right (16/9)
> }
>
> Bryan

Bryan,

Wow! That was the secret! I had been playing with the res.ini, but to no
luck. I thought POV couldn't render right, as it stretched the image. I had
tried the different resolutions (mentioned on Wiki-P), but to no avail. I
had thought the problem was my understanding of HD. The "right (16/9)" is
the key. Thanks!

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Rune wrote:
> Bryan Heit wrote:
>> But pixels in an HDTV image are not square (aspect ratio of 1)
> 
> Yes they are.*

My mistake.  Broadcast and DVD pixels are non-square, HDTV is.  However, 
you still need the 16:9 conversion, as povray assumes a 4:3 aspect 
ratio.  As such a povray image rendered without the "right (19/9)" will 
be warped, as the image will get rendered as 4:3, and then stretched 
horizontally to 16:9.

Bryan

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cyberspittle <nomail@nomail> wrote:
> The "right (16/9)" is the key. Thanks!

  I really wonder how that could ever work since the correct line is:

right x*16/9

  That suggested line is actually "right <16/9, 16/9, 16/9>" which is
*completely* a different thing.

-- 
                                                          - Warp

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Warp wrote:
> cyberspittle <nomail@nomail> wrote:
>> The "right (16/9)" is the key. Thanks!
> 
>   I really wonder how that could ever work since the correct line is:
> 
> right x*16/9
> 
>   That suggested line is actually "right <16/9, 16/9, 16/9>" which is
> *completely* a different thing.
> 

Oops.  You need to put in the correct vector to make it work right.

Bryan

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Warp wrote:
>   I really wonder how that could ever work since the correct line is:
> 
> right x*16/9
> 

In my standard filebase is:
	right           x*image_width/image_height

So the aspect ratio will be always "correct" by default.

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

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Eero Ahonen <aer### [at] removethiszbxtnetinvalid> wrote:
> In my standard filebase is:
>         right           x*image_width/image_height

> So the aspect ratio will be always "correct" by default.

  Please read the caveats of that "trick" here:

http://tag.povray.org/povQandT/languageQandT.html#aspectratio

-- 
                                                          - Warp

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Warp wrote:
> 
>   Please read the caveats of that "trick" here:
> 
> http://tag.povray.org/povQandT/languageQandT.html#aspectratio
> 

Good points (except 1, which is poo, because rendering the scene with
unoriginal/unintended aspect ratio always disturbs it, except with case
3 ;)), thou they haven't disturbed me yet (4. seems to be one that
will). I usually render my scenes several times with multiple aspect
ratios to get more view, which makes the automation handy.

-- 
Eero "Aero" Ahonen
   http://www.zbxt.net
      aer### [at] removethiszbxtnetinvalid

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Eero Ahonen wrote:
> Warp wrote:
>>
>>   Please read the caveats of that "trick" here:
>>
>> http://tag.povray.org/povQandT/languageQandT.html#aspectratio
>>
>
> Good points (except 1, which is poo, because rendering the scene with
> unoriginal/unintended aspect ratio always disturbs it, except with
> case 3 ;)), thou they haven't disturbed me yet (4. seems to be one
> that will). I usually render my scenes several times with multiple
> aspect ratios to get more view, which makes the automation handy.

As a side note, if you want an automatic adjustment for image ratio that 
doesn't prioritize either horizontal or vertical angle, you can use:

up y*sqrt(image_height/image_width)
right x*sqrt(image_width/image_height)

This will for example have the effect that if you switch the width and 
height of the image, it will be like if you rotated a real camera 90 
degrees: the area will be the same.

Remember though that the effect will be overruled if the angle keyword is 
used.

Rune
-- 
http://runevision.com

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