Many of you have probably seen this at slashdot,

Here is a physical technique to interchange the roles of a camera and a
light-source which is reminds me of how POV-Ray calculates the rays.

See the (maybe slashdotted) page:
http://graphics.stanford.edu/papers/dual_photography/

download the 60MB movie and marvel at the card-trick at the end.

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

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Jellby <me### [at] privacynet> wrote:
> download the 60MB movie and marvel at the card-trick at the end.

  The page says it's a 9.6 MB video, and the link gives a 404.

-- 
                                                          - Warp

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On Tue, 10 May 2005 16:18:50 -0400, Warp wrote:

> Jellby <me### [at] privacynet> wrote:
>> download the 60MB movie and marvel at the card-trick at the end.
> 
>   The page says it's a 9.6 MB video, and the link gives a 404.

The page is wrong - it's 61 MB in size - and the demonstration is quite
amazing.  There might be some techniques in there that could be of use
here...

I'm not entirely convinced yet that this isn't a hoax, though - basically
what they're suggesting is that through their techniques, you could
reconstruct a hidden surface using the reflections off of a non-reflective
surface, but I'm not totally convinced that that's possible given the
dispersal of light.

But the video is still pretty cool. :-)

Jim

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On Tue, 10 May 2005 14:32:22 -0600, Jim Henderson wrote:

> I'm not entirely convinced yet that this isn't a hoax, though - basically
> what they're suggesting is that through their techniques, you could
> reconstruct a hidden surface using the reflections off of a non-reflective
> surface, but I'm not totally convinced that that's possible given the
> dispersal of light.

I should've included a <g> or something in there - I'm quite familiar with
SIGGRAPH (was a member aeons ago) and know the standards they require - so
the odds are quite low in fact that it is a hoax....

Jim

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<sigh>  And I was going to post the link to the Stanford site that hosts
the paper.  One of these days, I'll think in a straight line, instead of
scattergunning my thoughts all over the place...

http://graphics.stanford.edu/papers/dual_photography/

The document that describes this looks fairly interesting...

Jim

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> I'm not entirely convinced yet that this isn't a hoax, though -
> basically what they're suggesting is that through their techniques,
> you could reconstruct a hidden surface using the reflections off of
> a non-reflective surface, but I'm not totally convinced that that's
> possible given the dispersal of light.

That demo is *cool*.

I don't see why it isn't possible.  The projector is lighting one tiny 
segment of the card at a time, if it hits a red bit, the book is going to be 
lit with a red hue, very easy to pick up by the camera.  Once it's scanned 
the whole card, it would be easy to build up the picture.

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Jim Henderson <nos### [at] nospamcom> wrote:
> The page is wrong - it's 61 MB in size - and the demonstration is quite
> amazing.  There might be some techniques in there that could be of use
> here...

  Reloading the page helped. It changed to a link to a torrent.

  Now, I have to admit I'm at a loss about how to play that .mp4 file.
Winamp opens it ok, but plays the audio only, no video. Windows media
player (version 9 in Windows XP) refuses to play it altogether ("Windows
Media Player cannot play the file."). The Core Media Player does not
recognize the format at all. The Video Inspector utility (which can be
used to determine if codecs needed by multimedia files are installed in
the system or not) does not recognize the format either.
  I have run out of ideas.

-- 
                                                          - Warp

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"Warp" <war### [at] tagpovrayorg> wrote in message
news:42812631@news.povray.org
> Jim Henderson <nos### [at] nospamcom> wrote:
>> The page is wrong - it's 61 MB in size - and the demonstration is
>> quite amazing.  There might be some techniques in there that could
>> be of use here...
>
>  Reloading the page helped. It changed to a link to a torrent.
>
>  Now, I have to admit I'm at a loss about how to play that .mp4
> file. Winamp opens it ok, but plays the audio only, no video.
> Windows media player (version 9 in Windows XP) refuses to play it
> altogether ("Windows Media Player cannot play the file."). The Core
> Media Player does not recognize the format at all. The Video
> Inspector utility (which can be used to determine if codecs needed
> by multimedia files are installed in the system or not) does not
>  recognize the format either. I have run out of ideas.

QuickTime played it for me.  But Winamp did just audio, WMP seemed to freeze 
the image after a few seconds, and DivX player did video only!

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Warp wrote:
>   Now, I have to admit I'm at a loss about how to play that .mp4 file.

It is a regular MPEG-4 file,not even MPEG-4 Part 4 (aka H.264).  Probably 
anything that can play a modern Divx file can play it.

	Thorsten

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Thorsten Froehlich <tho### [at] trfde> wrote:
> It is a regular MPEG-4 file,not even MPEG-4 Part 4 (aka H.264).

  I thought H.264 was part 10.

>  Probably 
> anything that can play a modern Divx file can play it.

  How? I have tried everything.

  There's one good thing about the AVI format: The player does not need
to even know what is inside it. It just asks the system. If that mp4
file was embedded inside an AVI (instead of being on its own) I'm pretty
certain any of the players here would play it just fine.
  However, if that mp4 is a format all on its own (like eg. mpeg1 is),
then the player has to understand it, and every player which wants to
support it has to implement the support explicitly.

  (Note that I said "one". There are very bad things about the AVI
format. No need to remind me of that. :P )

-- 
                                                          - Warp

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