CGAL Mesh_3 generates undeterministic node ordering and occasionally non-repeatable tesselation

[fangq]

The original report and workaround were reported here:

http://cgal-discuss.949826.n4.nabble.com/Bug-infinite-refinement-for-CGAL-Surface-mesher-tp3024338p3026125.html

http://cgal-discuss.949826.n4.nabble.com/Bug-infinite-refinement-for-CGAL-Surface-mesher-td3024338.html#a3029510

https://groups.google.com/forum/#!topic/iso2mesh-users/SSsVyA_EUI8

[fangq]

Temporary workaround was committed in

https://sourceforge.net/p/iso2mesh/code/493/

still, the tet number may change because of the node ordering

[fangq]

Issue appears to be un-fixed in the latest CGAL release (4.6). Steps to reproduce this issue:

• download and compile CGAL 4.6
• cd example/Mesh_3, run "make mesh_3D_image"
• when complete, run

./mesh_3D_image
mv out.mesh out.mesh_1
./mesh_3D_image
diff out.mesh out.mesh_1

the files are different, both the node list, and element list.

• apply the following patch to set the RNG seed

--- mesh_3D_image.cpp_old   2015-06-12 16:34:46.000000000 -0400
+++ mesh_3D_image.cpp   2015-06-12 16:34:29.000000000 -0400
@@ -36,6 +36,11 @@
   CGAL::Image_3 image;
   image.read("data/liver.inr.gz");

+  CGAL::Random rd(1234567);
+  CGAL::Random::State st;
+  rd.save_state(st);
+  CGAL::default_random.restore_state(st);
+
   // Domain
   Mesh_domain domain(image);

• rerun the above test, the output files remain different - the mesh could not be reproduced.

[fangq]

issue closed. with the above patch for RNG seeding, I was able to produce deterministic meshes when using the latest CGAL release v4.8.1. looks like some recent upstream updates fixed the problem.