CGAL users discussion list

[Iasonm <>]

Hello,

I have some questions regarding the use of collapse_edge on a surface_mesh.

*Why I need it*
I am implementing  this
<http://visgraph.cse.ust.hk/projects/skeleton/skeleton_sig08.pdf>   for
educational purposes. The part 5 of this paper is called connectivity
surgery and it simplifies a previously contracted 2D mesh (after the
contraction process the volume of the mesh is so small that the mesh is
considered to lay on a plane). This connectivity surgery is in fact a mesh
simplification process using edge collapsing until no faces are left. On
each iteration of this process an edge is chosen based on some cost function
and it gets collapsed. I am thinking of using CGAL's collapse_edge function
to make the collapse. 

*My questions*
Since collapse_edge alters the connectivity of the mesh after each call to
collapse_edge I will need to call collect_garbage. 
1. In the reference manual of collect_garbage it is stated: "By garbage
collecting elements get new indices. In case you store indices in an
auxiliary data structure or in a property these indices are potentially no
longer referring to the right elements.". *Will collect_garbage() alter
parts of the mesh  that are not in the 1-ring area of the collapsed edge?
*This is important to me since if it doesn't I can just update the cost
matrix  (the one that is used to choose which edge will be collapsed on the
next iteration) to match the changes in the mesh. Otherwise I will need to
update the whole cost matrix which will be computationally costly.

2. Do you think there are other problems in using CGAL::Euler::collapse_edge
on a CGAL::Surface_mesh?  



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