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systems [21], interfaces and visualization systems. Augmented Reality aims at lifting
the support to pre, intra and post - operative visualization of clinical data a new level
by presenting more informative and realistic three dimensional visualizations [14]. Not
many years ago medical AR systems required expensive hardware configuration and
dedicated OS to handled real time superimposing and visualization process [35]. In
this paragraph the author will present portable augmented reality interface for visuali-
zation of medical data (also volumetric) for Windows OS environment that can be run
on off - the - shelf computer and test its capability. The main advantage of proposed
solution is speed, quality of rendering of virtual object and low hardware cost.
7.1 Augmented Reality Environment
For identification of the position of virtual object in the real scene the author used
size - known square markers. The transformation matrices from these marker
coordinates to the camera coordinates are estimated by image analysis. After thre-
sholding of the input image, regions whose outline contour can be fitted by four
line segments are extracted. Parameters of these four line segments and coordi-
nates of the four vertices of the regions found from the intersections of the line
segments are stored for later processes. The regions are normalized and the sub-
image within the region is compared by template matching with patterns that were
given the system before to identify specific user ID markers. The further details of
the algorithm can be found in [11]. The markers for the author's system are card-
boards with image patterns printed on one side (Fig 8).
Fig. 8 Set of image patterns (ARToolkit markers) used for AR software printed on one side
of cardboard
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