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Теория создания картинок SIRDS ↑

piter239 в посте Openmeta (оригинал в ЖЖ)

About Single Image Stereography


mso-ansi-language:EN-US'>3DMiracle & 3DMonster single image
stereography software toolkit is the result of scientific research concerning
the process of visualization of objects in human conscience and content
of hidden information in garblings of periodical structures.
Two types of stereograms are known today - Single Image Random Dot
Stereograms (SIRDS), and Single Image Stereograms (SIS) depending on whether it
is based on random dots or repetitive texture.
The principles of all single image stereograms are the same. Information
about the distance from some 3d object point to the observer is stored in the
distance between its projections on virtual surface (in this case the
surface of SIS/SIRDS stereogram) for both eyes.

If point B is farther than point A, than accordingly distance between projections dB is more than distance between it's projections dA. Let us consider an image filled with
horizontally repeating content. The repetition interval must be equal to the
distance between projections of the eyes for the most far point of virtual
object.
The contents of repeating strips may be random, or it may include some
information. During viewing such image by means of two eyes from the distance
close to calculated, you can perceive a plane behind a surface of the image. It
is the simplest stereogram.
If image contains some information about volumetric object behind a
plane, it is necessary to bring some amendment for each point while making
recurrence of strips in image. If a settlement period of recurrence is
designated as D, than the horizontal coordinate X [n]
for any point n can be calculated as

X[n] = X[n - 1]+ D - Zfactor

or

X[n] = X[n + 1] - D + Zfactor,


mso-ansi-language:EN-US'>where X[n - 1] and X[n + 1] are
points of accordingly previous and following cycles of recurrence, and Zfactor
= f(Z) is the amendment carrying the information about presence of the
three-dimensional image behind the surface. The real algorithm of rendering
stereograms is more complicated, but in any case it corresponds to the
specified principle.

EN-US'>Approximately 70% of people can perceive 3d objects in stereograms.

But what we actually see while observing stereogram? If we observe the
picture by means of only one eye, or if the picture is rotated on 90
degree, we will see nothing besides repetitive pattern. 3D object may be seen
only while observing correctly located image by means of two eyes. According to
the above algorithm, stereogram contains only the volumetric information, but
not a color or brightness information. In all other cases of depicting of
objects, the information is contained only in color or brightness. Therefore we
perceiving 3d object in single image stereograms in some different way. Actually
we perceiving it without habitual vision.
It may be illustrated by means of two stereograms, created with the same
texture, but containing information about different objects. In terms of
habitual vision the pictures are similar, but it is possible to perceive
different objects in each image.
Obviously volumetric information in stereogram is decoding in human brain, and
then transforming in visual forms and puting over the image. Hence this process
may be described as visualization of information calculated by brain. lang=EN-US style='mso-ansi-language:EN-US'>

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