CGAL Surface_mesher produces dense clusters of nodes

[fangq]

Quite often, cgalsurf (Surface_mesher class in CGAL 3.x) produces an unusually dense node cluster as a result of a focused surface refinement; sometimes, this refinement can result in an infinite loop which eventually exhausts the system memory. This issue was originally reported here:

https://sympa.inria.fr/sympa/arc/cgal-discuss/2010-11/msg00032.html

A maximum node number count limit was added to iso2mesh to prevent the infinite loop, but still, many users had complained about the sub-optimal mesh quality of the mesh with uneven node distributions. The previous user reports can be found here:

https://groups.google.com/d/msg/iso2mesh-users/Wx_EKVJSVSE/WEbGED42oXAJ
https://groups.google.com/d/msg/iso2mesh-users/aRll2B0BKm0/_CTeiyFMlMwJ
https://groups.google.com/d/msg/iso2mesh-users/UermqCPNY_g/BgHf32g-Pj0J
https://groups.google.com/d/msg/iso2mesh-users/N-kF7Tmoyqk/TnD_ZkKFH2kJ
https://groups.google.com/d/msg/iso2mesh-users/EeBtu_ZUyUY/HzrFVEOl3uYJ