fix-collapse.tar.gz
Modified checks in MMG5_chkcol_bdy to prevent some unwanted collapses.

Several files are attached. ctest-logs-devel.txt and ctest-logs-fix.txt contain the logs of the continuous integration tests for both the unfixed (devel) and fixed versions of the code. Only mmg3d tests have been run (long tests included). For these tests, mmg has been compiled in Release mode, with 32-bit integers. Scotch is used in sequential mode (BUILD_PTSCOTCH=OFF) for reproducibility. Computing times are similar and adaptation waves are strictly identical with or without the fix.

test-devel.log and test-fix.log are the output of mmg for the following test (download input mesh):

mmg3d_debug mmg-PR227.mesh -hausd 0.5 -hmin 1 -hmax 5 -nr -nofem -xreg -m 7000 -v 10

The CoquilFace warning that appears in the devel version has been successfully removed with this update. However, another similar warning appears later in the remeshing process, which requires further investigation and will be the object of future update.

The configuration of interest for this update is as illustrated in the picture:

The collapse that is represented on the picture (point ip over point iq) merges two manifold edges that each possess exactly two boundary faces (hatched triangles on the picture). Hence, the collapse results in a non-manifold edge since there are now four boundary triangles in the shell of the edge. The modification of the topology of the mesh being unwanted, some tests have been modified in order to refuse such a collapse.