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Listing the geometric data in three tables provides a convenient
reference to the individual components of each object. Also, the object
can be displayed efficiently be using data from the edge table to draw
the component lines. Here I discuss about how to create those tables
with the help of C++ code.
Vertex table consists of the array of vertices with the coordinate value
of each vertex. In C++, a vertex table can be created by creating a
class that has . For example
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| class vertex{ private: Point3D *points; public: vertex() { points = new Point3D(); }}; |
Edge table consists of pointers back into vertex to identify the edges for each polygon. For example,
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| class edge{ public: vertex *ver1; vertex *ver2; bool done; //1 if edge not to be drawn: //0 if edge to be drawn, avoids multiple drawing of the edges edge *adjsur; //pointer to adjacent surface's edge edge() { ver1 = new vertex(); ver2 = new vertex(); done = false; }}; |
Surface table consists of pointers of edges associated with the surface.
Similarly it consists of Coefficients of Plane equations A, B, C, D and
color intensity value of each surface. Surface table has great
importance in Surface Rendering and Visible surface detection. The
surface table can be created in C++ as
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| class surface { public: edge *edges; float A, B, C, D; int icolor; surface() { edges = new edge(); A = 0.0f; B = 0.0f; C = 0.0f; D = 0.0f; icolor = 0; } } |
Rules for creating Geometric table:
1. Every vertex is listed as an end point for at least two edges.
2. Every edge is part of at least one polygon
3. Each polygon has at least one shared edge.
4. Every surface is close.
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