The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
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Three are the main objects of the urban environment to 
represent in 3D: relief, sidewalks and buildings. The altimetry 
controls begin to validate the elements in an isolated way and 
latter in the geographical context in which they are located. 
The interaction and navigation is carried out when the 
Modulo3D is activated, showing the work scene from different 
perspectives and amplifying degrees, with a pleasant 
visualization and a flexible displacement in the face of a 
realism that includes lights and shadowing of the objects. 
Indistinctly, views 2D and 3D are activated. Only with this 
processing the observer's and he camera position change, by 
using the Zoom, Pan tools and by Drawing elements, without 
modifying the identification of the associated object. 
It is in the view 3D where each object is three-dimensionally 
modeled transforming it into a solid, out of: 
• Determination of the height of the objects on the terrain. 
• Orthogonal Projection to the surface. 
• “Blending the solids 'objects with common faces. 
3. GENERAL STRUCTURE OF THE MODULE 
The general structure of the three-dimensional treatment module 
is represented in the figure 2, indicating the main parts that 
integrate it. 
3.1 Classes structure 
f- Code Comment Web Report 
Solución | Proyecto 
® M°d«io3o.Bsp Modulo3D Proyecto 
Si Modulo3D.Edas 
£1 Modulo3D 
15 Modulo3D.Movement 
B3 Modulo3D.Objects 
IS Nodulo3D.Tools 
a 
Modulo 3D.Tools.Read3DPoii 
Figure 2. Structure of the Modulo3D application 
Modulo3D offers a library of classes (DLL) on the 
platform .Net with the intention of facilitating the necessary 
functions for the visualization and three-dimensional interaction 
of the geographical information, thus being integrated to the 
CartoSIG system in an easy and robust manner. 
Classes: 
• Library of Structures of data fEdas and BSP): Encapsulates 
the classes representating the structures of data: Lists, Edges, 
Balanced Tree (AVL), and Binary tree of Partition of the 
Space (BSP), dedicated to improve the temporary costs of 
the algorithms due to their high search and storage costs. 
• Library Módulo 3D (Modulo 3D): Allows the exchange 
through the functions: 
o Selection: Activation of selection and consultation 
mode. 
o Pan: To travel on the scene. 
o Zoomln and ZoomOut: Magnifying and Diminishing 
o Textures : Defines the association patron of textures, 
o Mesh: To visualize in wire mode, 
o CreateWindow: Creates the window OPENGL 3D, 
knowing the beginning width and height coordinates, 
o LoadTextures: Loads the textures specified in the 
textures.xml file. 
o CreateWorld: Creates the world or scene to visualize, 
to which the objects that conform it will be added, 
o TerrainFromArray: It creates a terrain taking the 
points from the list that conforms it. 
o TerrainfromFile: It creates a terrain from the 
information the " .SRG " file type contains the points 
that conform it. 
o PoligonFromArray: It creates a polygon out of the 
points stored in a list, with its own color, keeping its 
identification so as to interact with it in mode selection, 
o CreateObserver: The observer is created, with its 
window and world associated to carry out the 
visualization. 
o DestroyWindows: It closes the window created with 
OPENGL 3D. 
o Colors: Define the palette of colors when it is 
visualizing without textures. 
• Movement Library: Contains the Camera, This class allows 
to carry out all the necessary functions of panning, zooming 
as well as moving in a specific direction for looking at a 
scene. The class Observer controls all the camera 
movements and show the scene (Render). These movements 
are defined by the user by means of the keyboard and the 
mouse. 
• Objects Library: three dimensional hierarchy of objects with 
simple and compound objects (e.g., the world or scene that it 
will visualize). The objects are the components of the 
diverse layers in which the geographical information to 
visualize is organized, that is to say, terrain, the layer relief 
and polygons, of the layer areal with the information 
corresponding to the sidewalks and buildings of the map in 
question. 
• Tools Library: Offers the common auxiliary tools for all the 
types of classes of the system. 
o IOSourceFile: Reads the information of the file with 
extension SRG (System of Graphic Representation) 
characteristic of the CartoSIG system; 
o TexTureList: It loads the objects' textures defined; 
o ThreePoint: It defines the points in three dimensions (x, 
y. z); 
o WinApi: It exports the functions of the libraries of 
Win32 to capture the mouse and its current position, 
and 
o Utils: it encapsulates the data common to the 
information visualizing 3D and it operates with the 
graphic functions of OpenGL. 
4. IDENTIFICATION OF OBJECTS AND ALGORITHMS 
TO MODEL 
CartoSIG manipulates the elements according to the classic 
distribution adopted in the SIG: points, lines and shapes; to this 
version the type of relief layers is added. 
The modeling of the objects is divided in two groups attending 
to their topologies: