On Wednesday 09 February 2005 17:54, Richard Ellis wrote:
> Why kind of post pov-ray processing are you anticipating? If you
> really want max quality, you'll get that by doing as little as
> possible to the pov-ray output images before feeding them into the
> mpeg encoder. Not to mention that noise free, crystal clear pov-ray
> images are just the types of images that best fit mpeg2 motion
> compensation. I am assuming here that you are rendering a pov-ray
> movie (with motion) and not just a still sequence.
>
Yes, I'm creating animation sequences.
> On Tue, Feb 08, 2005 at 11:18:05PM +0000, John Gay wrote:
> > On Tuesday 08 February 2005 21:00, Roine Gustafsson wrote:
> > > On Tuesday, Feb 8, 2005, at 17:27 Europe/Stockholm, John Gay wrote:
> > > > I'm also thinking about trying 4196 X 2304 frames to scale down to
> > > > 1024 X 576.
> > >
> > > That is actually not the best way. Render in the final resolution
> > > and let the renderer do the subsampling is always best. It can
> > > also be very much faster, since the renderer can optimize the
> > > subsampling.
> >
> > But the renderer still produces whole pixels, which I can see in
> > the frames and the mpeg output. even using AA without jitter. I was
> > hoping the scaler could fix this.
>
> But you said above that you wanted max quality. Technically, that is
> "max" quality. Pov-ray created a pixel, the mpeg encoder faithfully
> reproduced that pixel.
>
> But I think you are trying to fix problem A by applying a solution
> for problem B. I surmise that what you are finding is that pov-ray
> is too perfect, in that non-horizontal/vertical lines show pixel
> stair-stepping.
That's called aliasing, and POV-Ray does have the capability to cope with this
to some degree using Anti-Aliasing by super-sampling the pixels, but I'm
still seeing artifacts in the image. I was hoping that I could use the
mjpeg-tools to get rid of these.
> In which case, instead of trying to utilize a
> possible side effect of a tool that was never intended to to do the
> job you are looking for, you should be investigating ways to convince
> pov-ray to output the images in the form you want. If you want
> smooth lines, try to find a way to have pov-ray do the edge smoothing
> for you. Or investigate other tools that will take a set of super
> sharp computer generated images and apply a smoothing to them.
> Because if you depend on a side effect of the scaler, you may find
> that if the scaler algorithms change a few months from now, that your
> side effect you depend upon disappears in the process.
>
I'll play around with AA a bit more. I'll see if ImageMagick or The Gimp can
fix these. I'd prefer something I can batch-process.
> > > > I still need to work on my modelling, but there are plenty of
> > > > POV-Ray models on the Internet if you know where to look. Any
> > > > other comments/suggestions about rendering images for wide
> > > > screen DVD resolution would be good on this thread.
> > >
> > > Remember to think about non 1:1 pixel aspect ratios, and plan for
> > > interlacing. Also remember some RGB colors are invalid Y'CbCr so
> > > preview your test renderings in Y'CbCr before the final render.
> >
> > I know. POV-Ray creates 1:1 pixels. the scaler should convert these
> > to the proper aspect for wide screen. POV-Ray can also generate
> > interlaced frames.
>
> Maybe you should consider suggesting to the pov-ray development team
> the possibility of modifying pov-ray to generate non-square pixels.
> If they are already allowing the generation of interlaced frames,
> they are trying to be somewhat aware of "video" usages for pov-ray
> models. Well, in order to properly be "video" usable, non-square
> pixels are also a requirement.
>
But which of the many non-square sizes should they support? And why should
they spend time with that when video-based tools, like mjpeg-tools already
contain converters for this very purpose? POV-Ray is primarily for creating
computer images mainly displayed on computers or printed. When it's used to
generate animation sequences, these need to be converted to what ever video
format by other tools, which already contain scaling tools.
> You will get your best quality if pov-ray directly generates
> non-square pixels than by any post-processing to convert square
> pixels into non-square pixels.
>
Yes, but the POV-Ray team already have their hands full creating more
interesting rendering effects than adding support for several non-square
pixels that would only confuse everyone except us video making guys.
But thanks for the input.
John Gay
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