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4.5.2 Texture balancing and blending 
Several images from different viewpoints have to be taken of 
the object. The same spot pictured from different viewpoints 
usually results in different colours due to different lighting 
conditions. If several images are mapped on a single triangular 
model, these differences create a visually very disturbing effect. 
To reduce these effects, the images need to be balanced on a 
global per image basis and finally blended locally along the 
transition between images. 
4.5.3 Texture mapping 
The main purpose for image calibration is to map the image 
onto the triangulated mesh. The texture mapping takes each 
triangle in the 3D model and computes the corresponding 
triangle in the 2D image, which is then mapped onto the 3D 
model. If a 3D triangle maps into more than one image, one 
image is chosen according to a set of confidence criteria (e.g. 
size of the texture triangle, direction of the local surface 
normal). Figure 4 shows three snapshots of the final textured 
mesh created from the Mantova data set. Alternatively to 
mapping the image on the mesh, the image calibration can be 
used to create a depth map for the image from the range data, so 
that the user can measure 3D coordinates in the original image. 
Furthermore, the image can be used to colour the point cloud 
with the true rgb values. 
Figure 4: Snapshots of the final texture-mapped 3D model 
created from the Montova data set. 
5. USING THE MODEL 
The data processing described in section 4 creates a texture- 
mapped 3D model of the surveyed object containing the 
complete geometric 3D information. This model can be used as- 
is for visualisation purposes, however, for most applications the 
user requires some tools with which he can extract application- 
specific information. These tools should be easy to use, even for 
a non-expert in laser scanning since the user of the final model 
is often not the person who acquired and modelled the data. 
This way the software becomes a virtual surveying tool, which 
extracts the information from the computer model and hands it 
over to standard CAD software for further usage. Examples for 
useful tools for Cultural Heritage applications are: 
• Point and distance measurements 
• Area and volume measurements 
• Interactive and automatic fitting of planes 
• Creation of cross-sections 
• Automatic extraction of orientation discontinuities 
• Creation of ortophotos 
• 3D visualisation of vector data (cartography) 
Examples of applying some of these tools to the 3D models are 
shown in Figure 5, Figure 6, Figure 7 and Figure 8. 
Figure 5: Snapshot of the textured Hera model together with 
vertical and horizontal sections, which were created 
with the virtual Surveyor and transfered to Autocad. 
Figure 6: A set of cross-sections that were created in the 
Surveyor from the Mantova model and then 
transferred to Autcad.