Tuesday, February 2, 2010

wonderful world of stere-ereo



well its not pretty - but here it is - my first stereo image...
youll need red and blue glasses !

some stereo volumes from the viewport:


and some notes from the web:
Notes from wikipedia
basics:
anaglyph images are used to provide a stereoscopic effect.

2 colour glasses - each colour chromatically opposite
each colour blocks out the opposing light waves leaving near black

each image is superimposed (additively) but offset with respect to each other to produce the 3D effect
ususally the subject is in the middle with the forground and background shifted latterally in opposite directions

~the visual cortex of the brain fuses this into perception of a 3D scene or composition

most glasses are red on the left eye and cyan on the right
red and blue is cheaper - but there is a improvement in image
especially when viewing skin tones with a cyan filter

anaglyphs are easier to view than parallel (diverging) images or cross viewd pairs stereograms (magic eye ? )

Anaglyphs can be made in two ways
1 using two cameras offset from each other and convering - aiming toward the same subject
with different filters on each camera

2 on a computer by using pixel operations instead of the filetrs to knock out each color - and the offset can also be done digitally

** NB you stil need two base images when creating anaglyphs digitally

in photoshop - you can adjust the colours for the images and screen them back onto each other

TERMS
IAD  Inter Axial Distance / IOD inter-occular Distance
can we assume inter occualar refers to eyes interaxial refers to camera lenses.
http://forums.creativecow.net/thread/268/43#51
IPD - inter-pupillary distance
is considered the correct term for the measurement of the distance between the left and right eyes of the viewer.

IOA inter axial Angle - this refers to convergence - the angle the cameras are pointing in
toward the subject - also called `toeing` in

Parallax (wikipedia) fro greek parallaxis - "alteration"

In the art of stereoscopy, screen parallax is defined as a measure of the distance between
left and right corresponding or homologous image points when such points are projected
on a screen.
homologous from greek 'to agree'
biology : similarities between charateristics of organisms eg forelimbs in mammals
wikipedia:
Parallax is an apparent displacement or difference in the apparent position
of an object viewed along two different lines of sight.

It is measured by the angle of inclination between the two lines of sight.

Nearby objects have more parallax than distant objects - therefore you can measure distances
Stellar parallax provides the basis for all distant measurements in astronomy.
Stereopsis:
Many animals, including humans, have two eyes with overlapping visual fields to
use parallax to gain depth perception; this process is known as stereopsis.
Lenticular is the adjective relating to lens.

AutoStereo - general term to descripe the stereo effct from a device that does not require glasses
(either anaglyphic or lenticular)

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Houdini Notes
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Houdini has an asset which is a built-in stereo cam rig with controls for IAD
and ZPS - Zero Parallax Setting - which controls the convergence point.

in mplay the left image scan be viewed as C and the right can be viewed as C2

IAD - the distance between the two cameras - the center of the lenses ?
ZPS - Zero parallax screen - houdini make a plane where points of the
two images intersect

*     The ZPS coincides with the viewing screen
*     Objects between the camera and the zps,
    or in front of the ZP appear to be in front of the screen
*    Objects behind the ZPS in 3D, appear to be behind the screen

* when there is no IOA (angle) - ie the cameras are parallel - the
convergence plane appears to be just 'beyond infinity' - or as far as the eyes can see.

* there doesnt seem to be a control for IOA on the Houdini StereoCamera
- the cameras are paralell
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* "...the big caveat with toe in, is it creates geometric distortions
due to symmetric keystoning. "

http://forums.creativecow.net/thread/268/134
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Algoythmic Interaxial Seperation Reduction
(to produce lower parallax values)

http://www.freshpatents.com/Algorithmic-interaxial-reduction-dt20080228ptan20080049100.php

In the art of stereoscopy, screen parallax is defined as a measure of the distance between
left and right corresponding or homologous image points when such points are projected
on a screen.

homologous from greek 'to agree'
biology : similarities between charateristics of organisms eg forelimbs in mammals
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LINKS

Professional Anaglyph camera rigs
http://www.3dfilmfactory.com/3d_camera_rigs.html

French dude worked on meet the robinsons
makes his own anaglyphs and camera rigs
http://bernard.mendiburu.free.fr/pro/book/movies/

Avatar

Imax Cineams
http://www.imax.com/

Wikipedia :  Lenticular Lenses
http://en.wikipedia.org/wiki/Lenticular_lens/

Lenticular Prints
http://www.gorillaprint.com.au/index.php?/print/lenticulars.html

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