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Title
Proceedings, XXth congress

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004


the building models, is used; while ground images collected
from handheld cameras are used for wall textures.
3.1 Roof Texture
The scanned aerial photo is used to create roof texture. To avoid
many small image files, all building roof objects in the study
area are associated to their texture images at one time based on
the photogrammetric principle. The collinearity equations are
involved in this calculation for image data retrieval. However, it
is not efficient to associate the texture image to the roof object
with rigid photogrammetric model every time when we display
the building model. To solve the problem, we generated and
used the ortho-rectified image in which the image values have
the same coordinates system as building roof model. After that,
we can define the relationship between images and 3-D building
objects directly for texture mapping. The location of the image
segment for a building roof texture in an aerial image and
orientation are most important parameters to map the texture. In
this paper, an ortho-rectified image, which has contents only
inside each building boundary and contains null outside, is
generated as building roof texture. This is accomplished by
enhancing current ArcGIS with advanced photogrammetric
capabilities to handle model based true ortho rectification.
Figure 3 presents an example of such generated ortho image for
roof texture.

(b)
Figure 3. Texture Images for Roofs (a) and Walls (b)
3.2 Wall Texture
The building wall pictures were taken on the ground to create
the wall textures with a digital camera and a 35mm roll film
camera. In case of roll film camera, we got the image after
18
developing and scanning using a desktop scanner. For the wall
texturing, we use a different way with roof texturing. Each wall
is related to one individual image file. In addition, the wall
texture is directly corresponding with view plane without 3-D
building model. The detail methodology about the
correspondence between the wall objects and image files and
the association with view plane will be discussed in next section.
4. PHOTOREALISTIC MODELING
Once the geometric models and texture images are prepared, the
photorealistic building model can be generated using the
ArcObjects programmed and embedded in ArcGIS for this
study. ArcObjects are a set of computer objects specifically
designed for programming with ArcGIS Desktop applications
base on the object-oriented programming (Zeiler, 2001). We
use such development to automatically select wall texture
images and associate them to the geometric building model.
Figure 4 illustrates the general procedure for generating a
photorealistic model by integrating all necessary data.
3D Geometric model
Ortho-rectified
Roof Texture

Ground Image



Photo-realistic 3D Model
Figure 4. Photorealistic 3-D Model Generation
with Data Integration
After generating the 3-D geometric building model, the building
roof can be textured using the ortho-rectified image segment
that is generated with aerial photo image. The assignment of
texture image to the right building objects is accomplished by
using the geometric relations between 2-D coordinates of texel
and 3-D coordinate of building model through the orthographic
projection equation. Twelve parameters are required to
represent the 3-D object on the 2-D view plane as shown the
following homogeneous transform matrix (Hearn, et, al, 1994).
In this matrix, 2 and v are pixel coordinates in screen, X, Y, and
Z object coordinates, R rotation matrix with element Ri, / shift,
@&% 44, and v intrinsic parameters and s and 7 perspective
parameters.