International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
  
Figure 6. 
Strips of points useful to support conventional drawings 
  
Figure 7. Detail of the triangulated model 
reduced enough; a decimation with curvature sampling originates 
instead, in the triangulation phase, a surface with mesh of variable 
dimensions according to the complexity of the object. 
On the other hand, operating only with automatic procedures, it 
can be hard to regulate the decimation level without losing too 
much data in the uniform areas with the result also to produce 
  
   
     
  
Figure 8. 
Sample of the triangulated model without simplification 
holes in the meshes. In other case study, with more regular 
geometries, we obtained a positive outcome with a manual 
selection of portions of the cloud and with the application of 
different levels of curvature sampling. 
3.2.3 Triangulation: The cloud of points, after registration and 
pre-processing operations as we have described above, is an 
important “storage” of metric documentation. It is possible to 
extract punctual dimensional information or to select “strips” of 
points to support the drawing of conventional plans and sections 
or to proceed in a sort of restitution identifying lines of 
discontinuity with manual or semiautomated procedure that 
analyze the curvature. More often the cloud of points needs to 
be transformed into surfaces: a triangulation converts the given 
set of points into a consistent polygonal model (mesh). 
3.2.4 Polygons editing: Finally, different kinds of elaborations 
can be performed on the model of surfaces, according to the 
requirements that the graphical output should have, in order to 
satisfy our aims: static views, shaded or texturized, interactive 
exploration from local workstation or the Internet. 
As we know, the editing of the model must balance two opposite 
needs: on the one hand it is necessary to take into account the 
“weight” of the model and, on the other hand, the geometric and 
topological description must be preserved. The decimation of 
Figure 9. Polygon editing: 
a - detail of the starting model; b - decimation (1% triangle) 
without edge reconstruction and fixed breaklines; 
c - automatic breakline detection, supported by 
curvature surface analysis; 
d - edge reconstrution; e - the same detail after edge 
reconstruction; f - decimated model (1% triangle) with 
fixed boundaries 
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