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feeling. Using texture mapping repeatedly to implement reflection, refraction, con-
cave-convex, transparency and other effects, can paint the model surface more exqui-
site and realistic(See Fig.1). At the same time minimizing the face number in scene
can improve the real-time rendering speed in virtual wandering. Unfortunately when
the user reaches a very short distance to the object, maps instead of detail models look
too flat than our real world.
Fig. 1.
Repeated use of Cutouts to express details
3.2
Reconstruction Based on Image Feature Points Matching
As for the complex-shaped sculptures in this courtyard, the method, which based on
matching image feature points, can be adopted to obtain a lifelike effect with a high
speed. The reconstruction of space feature points can be done first by computing the
position according to its projections on different imaging planes. The object's geome-
tric model under three-dimensional space can be rebuild based on these 3D points.
Take a stone lion as an example, the approach can be decomposed into four steps:
firstly, use a hand-held camera to capture the appearance of the sculpture of interest
from a number of different overlapping views; secondly, compute camera parameters
and 3D coordinates of the matched points by assigning their exact position in different
photos; thirdly, rebuild enough 3D feature points of stone lion; and finally link these
points in a correct sequence to rebuilt a mesh topological structure.
Let
C
1
and
C
2
respectively denote the local coordinate systems from two camera po-
sitions, the corresponding transformation parameters are
R
1
,
t
1
,
R
2
and
t
2
. For a point
P
with the coordinate
Xxyz
in the world coordinate system, its coordinate is
(, ,)
ww ww
Xxyz
in
C
1
, and
(,
,
)
Xxyz
in
C
2
, which allows us to write
(,
,
)
c
11 11
c
c
c
c
2
c
2
c
2
c
2
X = RX + t
X = RX + t
C1
1
W
1
(1)
C2
2
W
2
This can be rewrite as the transformation relation between
C
1
and
C
2
-1
-1
X
=RR X
+t -RR t =RX
+t
(2)
C
1
2
C 1
1
2
2
C
1
2
2
Once the positions in two photos of point
P
are confirmed, we can obtain the rela-
tive spatial relation between the two coordinate systems by the equation above.
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