At this moment I am rendering a video I did about 14 years ago or so.
(before YouTube...)

See: https://www.youtube.com/watch?v=s0o0fgmyYYk

This remake will be in Full HD 1920 x 1080 pixels and at 30 fps.
The total video takes 10920 frames, so it will take a while :-)

I render with AA = 0.3 and Q = 9

And now for the questions:

I understand that you can let Povray render a 32 bpp image R G B + transparency
PNG file.

To do so I used:

  Output_Alpha = 1

and I changed my background to:

  background
  {
    rgb < 0.8 0.8 0.6 >
    transmit 1.0
  }

It looks like it works:
- the output file is a little bigger.
- when I view the output in Irfanview and select the Alpha Channel I see my
object ( a Piston) in white on (If I remember well) a black background.

QUESTION:

- Am I correct to assume that Povray only makes the rays that DO NOT hit an
object transparent?

- If I specify a greenish background and that colour also appears in my
rendering, is ONLY the background transparent? Or also part of my rendering.

- How can I use a series of Povray images to create an animation?
- - Years ago I used VideoMach. Are there better tools?
- - Are there tools to merge my animation with another video?

What I would like is a way to show my animation 'in front' of another video.
Like Blue or Green screen technique used for film and TV.


Any help is much appreciated,


- Olaf AKA Satadorus -

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"Satadorus" <nomail@nomail> wrote:

> - Am I correct to assume that Povray only makes the rays that DO NOT hit an
> object transparent?

Funny you should ask about this, as I just looked it up a day or so ago, and
have been using it - it works fine.
use +ua in the command line, and don't use ANY background or skysphere
declarations.

> - How can I use a series of Povray images to create an animation?
> - - Years ago I used VideoMach. Are there better tools?
> - - Are there tools to merge my animation with another video?

I use Video Mach, since it's simple and intuitive to use.
I've asked here before, and did some extensive searching when I wanted to
"upgrade" my software, but I didn't really find anything that stood out.
I use Format Factory to convert file formats.

> What I would like is a way to show my animation 'in front' of another video.
> Like Blue or Green screen technique used for film and TV.

Perhaps if you split up the background video into separate frames, you could
display that frame behind your POV-Ray scene and have that be the background for
your renders.   Then just string the frames together as usual.

Sorry if I can't be of more help at the moment.

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Le 04/03/2016 21:02, Satadorus a écrit :
> QUESTION:
> 
> - Am I correct to assume that Povray only makes the rays that DO NOT hit an
> object transparent?

Well, transparent is area that was background only. And "half-transparent" the border
between object and background if you use antialiasing (yes, you do with AA 0.3)

> 
> - If I specify a greenish background and that colour also appears in my
> rendering, is ONLY the background transparent? Or also part of my rendering.

Colour is irrelevant, it's the background, as a concept, that is important.

> 
> - How can I use a series of Povray images to create an animation?
> - - Years ago I used VideoMach. Are there better tools?
> - - Are there tools to merge my animation with another video?

Depend on your platform.

I would go for ffmpeg and kdenlive, but I'm on linux (and tuning ffmpeg can be
painful).

> 
> What I would like is a way to show my animation 'in front' of another video.
> Like Blue or Green screen technique used for film and TV.
> 

You need a video editor, with multiple tracks... kdenlive :-)

If you have all the frames from both video, you can also do it by hand/script with
imagemagick, then encode the final result.

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On 04.03.2016 21:02, Satadorus wrote:

> - If I specify a greenish background and that colour also appears in my
> rendering, is ONLY the background transparent? Or also part of my rendering.

It doesn't work like a green screen. Parts of your render will not
become transparent just because they accidentally have the same color.
However if an object itself is partially transparent (e.g. glass) and
the background contributes to the rendered pixel I think it will be
partially transparent when rendered with alpha output (at least if
the file format supports that).

> - How can I use a series of Povray images to create an animation?
> - - Years ago I used VideoMach. Are there better tools?
> - - Are there tools to merge my animation with another video?

I use ffmpeg which is good and free. You must be (or get) comfortable
with using command line though (there may be GUI projects for it but
I never tried them)

> What I would like is a way to show my animation 'in front' of another video.
> Like Blue or Green screen technique used for film and TV.

I also think the easiest way to achieve this would be to extract
the frames of the background video. If you want to keep the clean
animation frames, create a separate animation in povray that only
serves to combine foreground and background images.

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example image:
http://news.povray.org/web.56d9fcdc4ecdf5285e7df57c0%40news.povray.org

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"Satadorus" <nomail@nomail> wrote:

> What I would like is a way to show my animation 'in front' of another video.
> Like Blue or Green screen technique used for film and TV.

> - Olaf AKA Satadorus -


I was just RTFM   (Don't judge me!)  and I came across this:

1.1.9.2 Video CaptureNote: Video Capture under Windows is currently disabled due
to stability issues. Since this is a windows only feature, this means that no
current official POV-Ray release has video capture. However the infrastructure
is still in place and the below documentation will remain as it will eventually
be re-enabled.

Video capture is an experimental feature that will certainly change prior to it
being considered stable (if indeed it is kept at all). Currently it is only
implemented on the Windows platform. Video Capture (vidcap) allows a video
source (e.g. webcam) to be fed into a rendering just as if it were a still
image. Currently, this is done by overloading the 'sys' filetype in image maps
(this will change in the future once a dedicated keyword is added for it).

Here is a simplistic example of an image map that will obtain an image from a
video capture device:

pigment { image_map {sys ":vidcap:" map_type 0} }
and a more complex one:

pigment {
  image_map {
    sys ":vidcap:width=640:height=480:double-buffer=0:skip-initial=0:gamma=1.0"
map_type 0
    }
  }
The requirements are that the image type is sys and that the image filename
starts with the text :vidcap:. The text following the :vidcap: (if any) is
considered to be additional options which are then provided to the
platform-specific video capture support code.



Looked PRETTY interesting.
Maybe there's some other fairly unknown features you could find, or maybe
there's a way to port the playback of a video into POV-Ray for use with the
above feature...

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On 3/4/2016 3:02 PM, Satadorus wrote:

> - How can I use a series of Povray images to create an animation?
> - - Years ago I used VideoMach. Are there better tools?
> - - Are there tools to merge my animation with another video?

As said, ffmpeg is where it's at.  If you're using Turbo Pascal, you can 
easily handle this.

It will take a pile of .pngs and make a video.
It will merge two videos together.
It can do green screen overlays of one video over another (so I've read).
It's really a swiss army knife. - It can stream video while overlaying :)

This is the command I use to make a 720p video.
ffmpeg  -y -r 30 -i tteoac-%d.png -i ../wavs/TortillaFlatUnderGlass.wav 
-i metadata.txt -s hd720 -crf 18 -map 0:0 -map 1:0 -map_metadata 2 -c:v 
libx264 -pix_fmt yuv420p ../out/tteoac.mp4

-y                - overwrite old tteoac.mp4 without asking
-r 30             - 30 fps
-i tteoac-%d.png  - read this pile of files as an input stream
-i blah.wav       - audio track
-i metadata.txt   - chapter markers (you can omit this)
-s hd720
-crf 18           - quality bigger is higher q
-map 0:0          - map .png to video 0
-map 1:0          - map audio to video 0
-map_metadata 2   - stream 2 is metadata
-c:v libx264      - select encoder
-pix_fmt yuv420p  - geeky video thingy
tteoac.mp4        - output file name


I remember watching this video. I love the csg "explanations".
(I've owned a CB650 for speed and GL1100 for grandpa mode)

--
dik

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Am 04.03.2016 um 22:27 schrieb Christian Froeschlin:
> On 04.03.2016 21:02, Satadorus wrote:
> 
>> - If I specify a greenish background and that colour also appears in my
>> rendering, is ONLY the background transparent? Or also part of my
>> rendering.
> 
> It doesn't work like a green screen. Parts of your render will not
> become transparent just because they accidentally have the same color.
> However if an object itself is partially transparent (e.g. glass) and
> the background contributes to the rendered pixel I think it will be
> partially transparent when rendered with alpha output (at least if
> the file format supports that).

This is indeed the case for transparent or partially transparent objects.

Note however that it is /not/ the case for reflections.

Also, if the background is not entirely transparent, neither will the
resulting image.

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http://www.videoliberty.org/articles/povray_animation_beyond_basics.html

He has TV playing in his POV-Ray animation.
He's got some example code to get you started.

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