The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
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The principles of the 3dimensional viewing technology have 
been categorized according to 
• methods for the spatial visualization of stereo mates 
projected without contact, 
• methods for the separation of spatial presented stereo 
mates projected in contact and 
• methods using virtually 3D models 
No part of this exclusive presentation of virtual 3D images are, 
e.g., methods using simple central perspective effects and/or 
shadow effects, or "continuous profiling", which are methods 
for 3D data determination by combining a successive queue of 
profiles, but not own methods for virtually 3D data perception; 
similar holds for the Moiré effect. Materialized 3D appearance, 
including the 3D mirror effect and real models are no methods 
for virtually but for real 3dimensional presentation.On the 
other hand so called 2.5 D visualization Techniques are 
included in the synopsis of table 1, as far as they lead to a real 
3D perception by applying the NuOptics method, which 
already dates back to Pulfrich (about 1900). This sample also 
indicates, moving back to basics in Cultural Heritage 
recording and documentation based on stereo views still 
shows a surprising potential for further research as well as 
for advanced practical applications,like the complete list of 
virtual 3D perception Techniques, compare table 1 and 
SCHUHR/KANNGIESER (2004) 
It is liked to emphasize, from a consequently dealing with the 
principals of spatial data perception, even the future of the 
whole computer industry might change. Here namely the so 
called FELIX 3D solid state 3D screen seems to become a 
real candidate for a new spatial PC generation in order to 
replace or to complete the 2dimensional screen 
generation.This screen type is suited for 3D Laser projection 
in color and in real time via 3D Laser for direct model 
perception without glasses.The FELIX-3D solid state is the 
successor of well known 3D cylindrical Plexiglas tube. 
Another matter of research still is the optimum base length to 
be applied for stereo views. There is no unique answer for the 
optimum base length or better, to define the optimum base-to 
(object-) distance ratio, as the baselines differs due to the 
preference of near natural or super elevated deep perception, 
see Figure 4. For ad hoc applications using normal and wide 
angle cameras for 3D documentation purposes, the empiric 
baseline to object distance ratio should be approximately 1:10. 
It is highly recommended, not to take only two shots, but a 
sequence of stereo mates, so called “2 by 2 photographs” 
with different baselines, and possibly to chose different 
appropriate stereo mate combinations according to different 
criteria, but see also WALDHAEUSL/OGLEBY (1994). 
To start up taking own stereo views of Heritage monuments, 
the object at least should be photographed twice with a single 
lens camera from partly different projection centers 
(positions), which gives the baseline. The same object part in 
the view-finder avoids vertical parallaxes and on the 
stereoscopic perception side, the eyes “excuse”about up to 5 
degrees deviations from parallel camera axis. 
Further open research topics for Technique and Arts 
aspects of 3D images are, e.g.„ the market potential 
including a catalog of sample applications of stereo views. 
Additional matters of research are the professional potential of 
existing Archives for 3D-pictures and 3D-movies, as well as 
the complete history for stereo imagery, including the photo 
plasticon, see Figure 7 and sample stereo views in figure 2,4 
and 8. Also matter of research are the potential of terrestrial 
stereo image blocks, as well as the potential of stereo 
panorama-views. Additional open research topics for 
Technique and Arts aspects are derived from the combination 
of stereo mates of different physical character, e.g., the 
(stereoscopic) effect of the combination of stereo mates 
showing different pixel size, the benefit of combining day- 
and night stereo mates, the effects of combination of "before 
and after" pictures for Change Detection purposes, the 
manipulation of (existing) real and synthetic 3D-images to 
achieve a required deep perception and the effects of the 
combination of different Sensor images (e.g., optical and 
radar). 
Anlother open research topic for arts aspects of stereo 
views is the critical dealing with the Genre-3D-photography 
showing portraits, Heritage Monuments (see figure 2, 3,4 and 
8) Architecture, Landscapes (see figure 2 and 4 ), Nature, 
Environment, Technology etc.. This in particular holds for the 
"master pieces", like in figure 1, 2, 3,4 and 8, but also for 
available stereo views in general, as well as for own stereo 
views. Other arts aspects in this respect are differences in 2D 
and 3D exposure from an artists point of view and the 
(Computer) Generation and/or manipulation of artist stereo 
views. 
Another research topic is the generation of a lost or a so far 
not existed stereo mate by analog and/or digital means, for, 
e.g., Monument reconstruction purposes and artificial 30- 
images of paintings etc.. A lost or missing stereo mate 
preferable should be taken from the real object. If at least a 
3dimensional model of the object is available, the single 
picture can be projected onto the real (white) model and the 
stereo mates can be taken by stereo photographs. Also virtual 
stereoscopic data presentation using digital stereo mates can 
follow this idea: The real model is replaced by the 
3dimensional model data, while the optical projection of the 
single photo onto the model is replaced by mathematical 
projection and the stereo mates are not obtained from stereo 
photographs but by applying mathematical projection 
equations calculating the synthetic horizontal parallaxes 
values. 
Figure 4. Early queue of 2 by 2 photographs for optimum 3D perception of the Roman bridge of the ancient silk road near Urfa 
(Turkey) as carried out by the 1 st author.