Information Technology Reference
In-Depth Information
This chapter introduces a complete analysis of the geometrical quality of 3D
content based on distortion analysis by linking shooting and viewing geometries.
Starting from previous related knowledge (
i.e.
, viewing and shooting geometries),
we'll show remaining the problems and model the possibilities of depth distortions
between the scene perceived by a viewer and the scene shot initially. Next, we will
present a shooting layout design scheme ensuring a desired depth effect (controlled
depth distortion or perfect depth effect) upon a pre-determined rendering device.
Finally, we will introduce derived shooting technologies (which are patent pending)
complying with this scheme and thus achieve qualitative 3D content on the previ-
ously given rendering device: 3D computer graphics software and 3D devices. We
will present these prototypes and some of their results.
2
Previous Related Knowledge
2.1
Viewing
3D image rendering, with or without glasses, is known to require “stereoscopic”
or “autostereoscopic” devices. All these devices make a spatial, colorimetric and/or
temporal mixing over a single region of interest (ROI area physically filled by the
displayed image on the rendering device) of
n
m
so-called “initial images” of one
scene shot from several distinct viewpoints. These systems allow to optically and/or
temporally separate the images reaching each eye of one or more viewers. In case
of stereoscopic systems, both images are emitted in a single optical beam indepen-
dently of the viewer's position in this beam [1, 2, 17]. However, autostereoscopic
systems separate the images in several distinct optical beams, organized for exam-
ple, in horizontal “range” of
n
images (
n
×
≥
2and
m
= 1) [4, 5]. We can also imagine
optical beams organized in both horizontal and vertical ranges. Then we dispose of
a matrix disposition of
n
2), each one transporting
a different image. Thus, all known devices broadcast alternately and/or simultane-
ously
n
×
m
optical beams (
n
≥
2and
m
≥
1) within one or several optical beams in such a
way that both eyes of a correctly-placed viewer get different consistent images (
i.e.
,
initial images and not combinations of them). Thereby the viewer's brain rebuilds
his depth perception by stereoscopy [18]. Even if the human visual system has a
tolerance as for epipolar alignment, ideal positions within this tolerance correspond
in particular to the eyes line which has to be parallel to the display's rows. Despite
this human tolerance, we calculate our images in such a way that they have a perfect
epipolar alignment for a well-placed eyes line.
So let's analyse the geometry of these devices the “viewing geometry” (Fig. 2)
which will constrain the compatible shooting layout.
A 3D rendering device mixes
n
×
m
images (
n
≥
2and
m
≥
m
images sharing out a ROI of dimension
W
(width) and
H
(height). Each image (image's index
i
=(
i
1
,
i
2
)
×
)is
supposed to be “correctly” visible (without much mixing with others) at least from
the chosen preferential position
E
i
. These positions are aligned upon
m
lines par-
allel to the rows of the ROI located at distance
d
i
2
,
i
2
∈{
∈{
1
,
n
}×{
1
,
m
}
1
,...
m
}
, from the device
