Full text: XVIIIth Congress (Part B3)

    
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Figure 10.1: Photograph of a room. 
  
Figure 10.2: Wire frame rendering of the geometric model of 
the surface with ~ 60000 elements (from Karner, in print). 
  
Figure 10.3: Rendering of the room using surface properties, 
geometry and illumination via a radiosity model 
(from Karner, in print). 
11 IMMERSION IN 3-D SCENES 
Surfaces are being perceived by a human computer 
operator when wearing stereo glasses. The object that 
is being viewed can be interacted with if a 3- 
dimensional cursor is placed in the field of view. The 
computer now needs to be able to track the position of 
the cursor as well as the position of the stereo glasses. 
As the cursor moves the computer is aware of those 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
motions and can establish a relationship between the 
virtual 3-dimensional object and the real position of 
the cursor. In this manner a user can edit a 3- 
dimensional object interactively. The user can also 
move freely with the head if the computer can track the 
position of the head and can change the 3-dimensional 
object’s visualization as a function of the viewer 
position. In this manner a fully 3-dimensional object 
could be inspected from the left or the right, from 
above or below depending on the position of the 
viewer's eyes. 
This is denoted as ,iimmersion* in 3-d scenes and we 
are describing an immersive user interface based on a 
3-dimensional object surface and the 3-dimensional 
cursor, accompanied by a tracked viewer. This concept 
can be a significant element in a chain that goes from 
sensor sources via point clouds to surfaces and 
realistic visualizations. The immersive user interface 
¢an support the quality control and editing in a fully 
digital environment at very modest to no additional 
equipment costs. 
12 OUTLOOK AND CONCLUSION 
In recent years we have seen a dramatic broadening of 
the ideas of surface reconstruction. We have described 
a generalization of these ideas from traditional photo- 
grammetric stereo mapping of topographic surfaces to 
the use of a whole range of techniques, all aiming at 
geometric modeling of the surface of terrain or fully 
3-dimensional objects. We have also shown a broaden- 
ing from the traditional measurement of surface points 
to the more modern integrated view of „digital visual 
information“, to include the information source in the 
form of images or raw surface measurements, to 
combine geometry and radiometry and finally to 
include the application in the visualization and 
interaction with 3-dimensional digital surfaces. 
The traditional problems of image matching have 
made slow progress. The human operator is still the 
best stereo measuring entity. The machine is capable 
to perform measurements the human cannot take such 
as ranging, operating with structured light, performing 
interferometry or doing altimetry. The human can use 
single image or stereo object reconstruction, not 
however any of the other techniques. In a trade-off 
between manual human-based surface reconstruction 
and automated machine vision the evolution is to- 
wards largely automated systems in which the human 
is merely the quality control and editing agent. This 
requires that efficient interaction with 3-dimensional 
data be available in a form that is near a specific 
application scenario. The geographic information sy- 
stem GIS is in the process of generalizing from 2 to 3 
dimensions, e.g. by converting the 2-dimensional 
multi-layer urban GIS into a CyberCity model. The 
requirements of planetary mapping, of automated re- 
mote sensing, or of industrial inspection all point to- 
wards an increased use of automated processes to 
model the geometry of a surface and to provide tools 
to also determine non-geometric properties. 
We believe that these developments need an inte- 
grating view that is capable of fusing various data 
sources and analysis methods. One obtains a toolbox 
of procedures so that human interaction is small and 
limited to improvement of the quality of surfaces. 
  
     
 
	        
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