CGAL users discussion list

[Josip Dzolonga <>]

Hello everyone,

After I perform some operations on the Delaunay data structure, I want to remove certain vertices from it and then continue with the processing. To avoid removing the same vertex more than once, I compare the points, i.e. 

std::set<Vertex_handle> toRemove;

std::set<Point> seen;

for(std::list<Facet>::iterator iter = grown->facets->begin();

        iter != grown->facets->end(); ++iter) {

       Cell_handle c = (*iter).first;

   int index = (*iter).second;

   Point p1 = c->vertex((index+1)%4)->point();

   Point p2 = c->vertex((index+2)%4)->point();

            Point p3 = c->vertex((index+3)%4)->point();

   // Do not remove points already removed from a neighboring cell

   if(seen.insert(p1).second) {

   toRemove.insert(c->vertex((index+1)%4));

   }

   if(seen.insert(p2).second) {

   toRemove.insert(c->vertex((index+2)%4));

   }

   if(seen.insert(p3).second) {

   toRemove.insert(c->vertex((index+3)%4));

   }

}

T.remove(toRemove.begin(), toRemove.end());

However, I get the same error as before (but is_valid() returns true :/):

CGAL error: assertion violation!

Expr: v == V[3]

File: /usr/include/CGAL/Triangulation_ds_cell_base_3.h

Line: 98

terminate called after throwing an instance of 'std::logic_error'

  what():  basic_string::_S_construct NULL not valid

Then, I wanted to reconstruct the whole triangulation from scratch after every cycle of the algorithm (not practical, but in desperate times need desperate measures), and then this part causes trouble

if(T.is_infinite(*iter)) { continue; } Triangle triangle = T.triangle(*iter); if(triangle.is_degenerate() || TrigPerimeter(triangle) < 0.1) { continue; } Point circumcenter = CGAL::circumcenter(triangle);

The call to the circumcenter functions fails, and I suppose that this is because I'm using an inexact_constructions kernel. Is there any trick around this, i.e. some condition/heuristic that will skip these triangles? Changing the kernel itself is of course a possibility, however it will introduce a lot of changes in the whole project (because it is assumed in most of the code that some CGAL functions return something castable to double).

Thank you very much,

Josip