In article <3eb95e15$1@news.povray.org>,
 "Andrew Coppin" <orp### [at] btinternetcom> wrote:

> Questions, questions...
> 
> Does anyone know the physics behind holograms?

http://www.wikipedia.org/w/wiki.phtml?search=hologram&go=Go
http://www.everything2.com/index.pl?node_id=615788


> More to the point, can I draw one with POV-Ray? :-)

A hologram requires optical effects that POV can not simulate directly. 
You may be able to get something close to what a hologram made with a 
very long wavelength would look like by combining functions, but it 
would not work very well and would be very slow.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

Post a reply to this message

In article <3eba08b7$1@news.povray.org>,
 "Andrew Coppin" <orp### [at] btinternetcom> wrote:

> OK, on reflection maybe I was a little unclear. (Reflection, get it? Hehe...
> eh... heh... oh never mind! :-P) What I ment was... can I put a hologram
> into a POV-Ray scene?

An actual hologram or something that looks like one? An actual hologram 
is not practical, but emitting media is all that is necessary for making 
something that looks like one.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

Post a reply to this message

> 
>> OK, on reflection maybe I was a little unclear. (Reflection, get it? Hehe...
>> eh... heh... oh never mind! :-P) What I ment was... can I put a hologram
>> into a POV-Ray scene?
> An actual hologram or something that looks like one? An actual hologram 
> is not practical, but emitting media is all that is necessary for making 
> something that looks like one.
> 
That's right...
Here is example :
< http://www.irtc.org/ftp/pub/stills/2002-06-30/ddreams.jpg >
(ok, it's not a _really good one_, but it's mine ;)


-- 
  ________ 
_/ __/ __/ The answer is 42.
 \__ \__ \_______________________________________________________________

Post a reply to this message

> http://www.wikipedia.org/w/wiki.phtml?search=hologram&go=Go
> http://www.everything2.com/index.pl?node_id=615788

Will check these out later...

> A hologram requires optical effects that POV can not simulate directly.
> You may be able to get something close to what a hologram made with a
> very long wavelength would look like by combining functions, but it
> would not work very well and would be very slow.

That's the information I was looking for.

Thanks.
Andrew.

Post a reply to this message

Andrew Coppin wrote:
> More to the point, can I draw one with POV-Ray? :-)

Could you fake a 3d hologram with some clever bounding - similar technique
to the 'infinity cube' ?

-- 
Rick

Kitty5 NewMedia http://Kitty5.co.uk
POV-Ray News & Resources http://Povray.co.uk
TEL : +44 (01270) 501101 - FAX : +44 (01270) 251105 - ICQ : 15776037

PGP Public Key
http://pgpkeys.mit.edu:11371/pks/lookup?op=get&search=0x231E1CEA

Post a reply to this message

In article <3ebbea18@news.povray.org>,
 "Rick [Kitty5]" <ric### [at] kitty5com> wrote:

> Could you fake a 3d hologram with some clever bounding - similar technique
> to the 'infinity cube' ?

I don't know what you expect from this...I can't see how you would get 
anything like a hologram this way.

You could make the hologram as an actual shape and just make it 
shadowless, and maybe fool around with the diffuse and transparency. (a 
hologram is transparent, it only adds to what is behind it)
Emitting media is probably the most accurate way, though...or at least 
the most like a real-world hologram. Unless you're talking about the 
silvery white-light things.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

Post a reply to this message

ABX <abx### [at] abxartpl> wrote:

> On Wed, 7 May 2003 20:25:47 +0100, "Andrew Coppin" <orp### [at] btinternetcom>
> wrote: > Does anyone know the physics behind holograms? > (...) > More to
> the point, can I draw one with POV-Ray? :-)
> 
> I have recently shared user_defined camera patch
> (http://news.povray.org/search/?s=user_defined) prepared for MegaPOV with
> http://www.bdp-optics.com/ . With this extension they are now able to
> prepare material to 'print' 3D images directly from POV script
> (http://news.povray.org/povray.binaries.images/31396/ ). I do not know
> details behind 'printing' method but you can ask them about details and
> ordering.

They are using lenticular screens, which feed each view to each eye,
giving you a stereo image. It's not a hologram, which gives you
effectively infinite views.

-- Kaveh

Post a reply to this message

Andrew Coppin <orp### [at] btinternetcom> wrote:

> OK, on reflection maybe I was a little unclear. (Reflection, get it? Hehe...
> eh... heh... oh never mind! :-P) What I ment was... can I put a hologram
> into a POV-Ray scene?

(Sorry for late response. I have not checked posts for a while.)

This is a very interesting problem I have been thinking about for a
while. I am actually what you would call a "holographer", but relatively
new to povray. My interest is to "preview" a hologram before I make one.
So I like to see if there are any distortions of the image when I move
relative to the hologram. For example, this happens when you change the
wavelength of the reconstruction beam to that of recording. For an
example of what I mean, you can look at 

http://www.bazargan.org/Swing.mp4

This is an animation done with povray, using the (forward) ray tracing
equations for obtaining a holographic image. The beauty of povray is
that it is an excellent language for putting in math formulae, and then
it renders and animates it for you!

Here is a more complex example:

http://www.bazargan.org/dispersion-comp.mp4

Here the 'object' is a horizontal line of spheres. The hologram is
viewed with polychromatic light, but the light has first been dispersed
with a diffraction grating, so that the final images are all in line.

Of course the animation you see is just a geometric grid, not what you
would "see". For instance the image is only visible by the observer (the
eyeball) when it is looking through the hologram itself, but it does
show the "swing" of a holographic image. This is already very useful for
looking at distortions, multiple-wavelength playback, etc.

The next challenge is to show a 'photorealistic' image of a hologram in
a scene. For example, you have a hologram hanging on a wall, illuminated
by a white light above it. I think we can apply the same ray tracing
formulae, but this time in a 'backward' or computer graphics sense. So
the hologram becomes a 'special' surface. When a scene is rendered, the
color of each pixel on the hologram can be calculated by taking into
account the recording geometry, the original wavelength, the final
reconstruction wavelength (or band of wavelengths) and the object. 

I am not really clear about how to do this, but I have in mind some kind
of 'function' for the hologram surface. I hope this can be done in a
single pass in povray. 

A very useful tool has been the Lightsys 3 macros:

http://www.ignorancia.org

which draw in a color approximating to the wavelength chosen.

-- 
Kaveh

Post a reply to this message

On Thu, 15 May 2003 18:46:00 +0100, kav### [at] delete_thisfocalimagecom (Kaveh)
wrote:
> They are using lenticular screens, which feed each view to each eye,
> giving you a stereo image. It's not a hologram, which gives you
> effectively infinite views.

Perhaps, but I just received output of my patch in this technic and it looks
very impressive.

ABX

Post a reply to this message

ABX <abx### [at] abxartpl> wrote:

> On Thu, 15 May 2003 18:46:00 +0100, kav### [at] delete_thisfocalimagecom (Kaveh)
> wrote:
> > They are using lenticular screens, which feed each view to each eye,
> > giving you a stereo image. It's not a hologram, which gives you
> > effectively infinite views.
> 
> Perhaps, but I just received output of my patch in this technic and it looks
> very impressive.

Oh, properly done, the result would be impressive indeed, and with pov
pictures, even more impressive. 

What I would love to do is to make a hologram from, say, 180 views from
pov. Give me a little time. I'm working on it. ;-)

-- 
Kaveh

Post a reply to this message