CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 02/10/2015 08:34 AM, Adam Getchell wrote:
> Is there a way to rebalance a Delaunay triangulation after a flip() on a
> facet?

what do you mean?

Sebastien.

> On Fri, Feb 6, 2015 at 12:23 PM, Adam Getchell 
> <
> <mailto:>>
>  wrote:
>
>     Sebastien,
>
>     Thank you!
>
>     In hindsight, it makes sense that the facet flip results in an edge
>     which violates the Delaunay condition.
>
>     Regards,
>
>     Adam
>
>     On Wed, Feb 4, 2015 at 11:32 PM, Sebastien Loriot (GeometryFactory)
>     
> <
>  
> <mailto:>>
>  wrote:
>
>         If you flip some edges in a Delaunay triangulation, the is_valid
>         will tell you that the triangulation is no longer Delaunay.
>         Use the dt.tds().is_valid() instead.
>
>         Sebastien.
>
>
>         On 02/05/2015 07:23 AM, Adam Getchell wrote:
>
>             I've also done tests on flips of (2,2) simplices, with the
>             same results
>             (triangulation validity violated), except that they don't
>             also violate
>             my time foliation. The code currently on GitHub reflects the
>             flips on
>             (2,2) simplices.
>
>             On Wed, Feb 4, 2015 at 10:07 PM, Adam Getchell
>             
> <
>  
> <mailto:>
>             <
>             
> <mailto:>>>
>  wrote:
>
>                  Hello all,
>
>                  For the following code:
>
>                  void make_23_move(Delaunay* D3,
>             std::vector<Cell_handle>* three_one,
>                                        std::vector<Cell_handle>* two_two) {
>                     // Pick a random (2,2)
>                     unsigned choice =
>             generate_random_unsigned(__three_one->size());
>                     std::cout << "We're picking (3,1) vector " << choice
>             << std::endl;
>                     Cell_handle to_be_moved = (*three_one)[choice];
>                     for (size_t i = 0; i < 4; i++) {
>                       if (D3->flip(to_be_moved, i)) {
>                         // Delaunay::flip_flippable(to___be_moved,0)
>                         std::cout << "Facet " << i << " was flippable."
>             << std::endl;
>                         break;
>                       } else {
>                         std::cout << "Facet " << i << " was not
>             flippable." << std::endl;
>                       }
>                     }
>                  }
>
>                  From:
>             
> https://github.com/acgetchell/__CDT-plusplus/blob/master/src/__S3ErgodicMoves.h
>             
> <https://github.com/acgetchell/CDT-plusplus/blob/master/src/S3ErgodicMoves.h>
>
>                  Invoked in the test:
>
>                  TEST_F(S3ErgodicMoves, MakeA23Move) {
>                     unsigned number_of_vertices_before =
>             T.number_of_vertices();
>                     unsigned N3_31_before = three_one.size();
>                     unsigned N3_22_before = two_two.size();
>                     unsigned N3_13_before = one_three.size();
>                     std::cout << "Number of (2,2) simplices before = "
>             << N3_22_before
>                               << std::endl;
>                     make_23_move(&T, &three_one, &two_two);
>
>                     // Now look at changes
>                     reclassify_3_simplices(&T, &three_one, &two_two,
>             &one_three);
>                     unsigned N3_31_after = three_one.size();
>                     unsigned N3_22_after = two_two.size();
>                     unsigned N3_13_after = one_three.size();
>
>                     EXPECT_TRUE(T.is_valid())
>                     << "Triangulation is invalid.";
>
>                  From:
>             
> https://github.com/acgetchell/__CDT-plusplus/blob/master/__unittests/S3ErgodicMovesTest.__cpp
>             
> <https://github.com/acgetchell/CDT-plusplus/blob/master/unittests/S3ErgodicMovesTest.cpp>
>
>                  I've run these tests a couple dozen times, and every
>             time there is a
>                  flippable edge the triangulation is invalidated, e.g.:
>
>                  Repeating all tests (iteration 9) . . .
>
>
>                  Note: Google Test filter = S3ErgodicMoves.MakeA23Move
>
>                  [==========] Running 1 test from 1 test case.
>
>                  [----------] Global test environment set-up.
>
>                  [----------] 1 test from S3ErgodicMoves
>
>                  [ RUN      ] S3ErgodicMoves.MakeA23Move
>
>                  Generating universe ...
>
>                  Pass #1
>
>                  Fixing foliation....
>
>                  Pass #2
>
>                  Fixing foliation....
>
>                  Pass #3
>
>                  Fixing foliation....
>
>                  Pass #4
>
>                  Fixing foliation....
>
>                  Pass #5
>
>                  Fixing foliation....
>
>                  Classifying simplices....
>
>                  Valid foliation: true
>
>                  Delaunay triangulation has 95251 cells.
>
>                  There are 29713 (3,1) simplices and 35628 (2,2)
>             simplices and 29910
>                  (1,3) simplices.
>
>                  Number of (2,2) simplices before = 35628
>
>                  Random number is 27858
>
>                  We're picking (3,1) vector 27858
>
>                  Facet 0 was flippable.
>
>                  Classifying simplices....
>
>                  ../unittests/__S3ErgodicMovesTest.cpp:82: Failure
>
>                  Value of: T.is_valid()
>
>                     Actual: false
>
>                  Expected: true
>
>                  Triangulation is invalid.
>
>                  [  FAILED  ] S3ErgodicMoves.MakeA23Move (2229 ms)
>
>                  [----------] 1 test from S3ErgodicMoves (2229 ms total)
>
>
>                  [----------] Global test environment tear-down
>
>                  [==========] 1 test from 1 test case ran. (2229 ms total)
>
>                  [  PASSED  ] 0 tests.
>
>                  [  FAILED  ] 1 test, listed below:
>
>                  [  FAILED  ] S3ErgodicMoves.MakeA23Move
>
>
>                    1 FAILED TEST
>
>
>
>                  --
>                  Adam Getchell
>             about.me/adamgetchell <http://about.me/adamgetchell>
>             <http://about.me/adamgetchell>
>                  "Invincibility is in oneself, vulnerability in the
>             opponent." -- Sun Tzu
>
>
>
>
>             --
>             Adam Getchell
>             about.me/adamgetchell <http://about.me/adamgetchell>
>             <http://about.me/adamgetchell>
>             "Invincibility is in oneself, vulnerability in the
>             opponent." -- Sun Tzu
>
>
>
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>
>
>
>
>     --
>     Adam Getchell
>     about.me/adamgetchell <http://about.me/adamgetchell>
>     "Invincibility is in oneself, vulnerability in the opponent." -- Sun Tzu
>
>
>
>
> --
> Adam Getchell
> about.me/adamgetchell <http://about.me/adamgetchell>
> "Invincibility is in oneself, vulnerability in the opponent." -- Sun Tzu