Coons style can be chosen via env var
Coons style can be chosen via env var

The surface creation method can now be chosen using
the environment variable TIGL_COONS_CONTINUITY. The
following options are possible:
 0: Uses GeomFill_StretchStyle
 1: Uses GeomFill_CoonsStyle
 2: Uses GeomFill_CoonsC2Style

By default (i.e. no env var is set), GeomFill_CoonsC2Style
is still used.

DLR-SC/tigl,DLR-SC/tigl,DLR-SC/tigl,DLR-SC/tigl,DLR-SC/tigl,DLR-SC/tigl