Practical Algorithms for 3D Computer Graphics, 2nd Edition

3.4. Making an e d g e list from a list of polygonal faces 79

3.4 Making an edge list from a list of polygonal faces

When producing a wireframe drawin g of a model or converting between th e data

formats of alternative 3D CAD and animation packages it is important to be

able to build a list of edges from a list of polygons.

It is straightforward to make a list of edges by creating one edge for each

polygon sid e, but most polygon s will share edges. The task of removing multiple

entries from the edge list becomes excessively time consuming as the number of

polygons increases. In the case of n polygons approximately 3n

2

tests need to

be performed to