1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
! ------------------------------------------------------------------------------
!
! Gmsh Fortran tutorial 13
!
! Remeshing an STL file without an underlying CAD model
!
! ------------------------------------------------------------------------------
program t13
use, intrinsic :: iso_c_binding
use gmsh
implicit none
type(gmsh_t) :: gmsh
integer(c_int) :: ret
real(c_double), parameter :: lc = .1
character(len=GMSH_API_MAX_STR_LEN) :: cmd
call gmsh%initialize()
! Create ONELAB parameters with remeshing options:
call gmsh%onelab%set('['//&
'{'//&
'"type":"number",'//&
'"name":"Parameters/Angle for surface detection",'//&
'"values":[40],'//&
'"min":20,'//&
'"max":120,'//&
'"step":1'//&
'},'//&
'{'//&
'"type":"number",'//&
'"name":"Parameters/Create surfaces guaranteed to be parametrizable",'//&
'"values":[0],'//&
'"choices":[0, 1]'//&
'},'//&
'{'//&
'"type":"number",'//&
'"name":"Parameters/Apply funny mesh size field?",'//&
'"values":[0],'//&
'"choices":[0, 1]'//&
'}'//&
']')
! Create the geometry and mesh it:
call createGeometryAndMesh()
call get_command(cmd)
if (index(cmd, "-nopopup") == 0) then
call gmsh%fltk%initialize()
do while (transfer(gmsh%fltk%isAvailable(), .true.) .and. checkForEvent())
call gmsh%fltk%wait()
end do
end if
call gmsh%finalize()
contains
subroutine createGeometryAndMesh()
real(c_double) :: curveAngle, angle, forceParametrizablePatches
real(c_double), allocatable :: tmp(:)
integer(c_int), allocatable :: s(:,:)
integer(c_int) :: l, f
logical :: includeBoundary
! Clear all models and merge an STL mesh that we would like to remesh (from
! the parent directory):
call gmsh%clear()
call gmsh%merge('../t13_data.stl')
! We first classify ("color") the surfaces by splitting the original surface
! along sharp geometrical features. This will create new discrete surfaces,
! curves and points.
! Angle between two triangles above which an edge is considered as sharp,
! retrieved from the ONELAB database (see below):
call gmsh%onelab%getNumber('Parameters/Angle for surface detection', tmp)
angle = tmp(1); deallocate(tmp)
! For complex geometries, patches can be too complex, too elongated or too
! large to be parametrized; setting the following option will force the
! creation of patches that are amenable to reparametrization:
call gmsh%onelab%getNumber(&
'Parameters/Create surfaces guaranteed to be parametrizable', tmp)
forceParametrizablePatches = tmp(1); deallocate(tmp)
! For open surfaces include the boundary edges in the classification
! process:
includeBoundary = .true.
! Force curves to be split on given angle:
curveAngle = 180
call gmsh%model%mesh%classifySurfaces(angle * M_PI / 180., includeBoundary, &
transfer(forceParametrizablePatches, .false.), &
curveAngle * M_PI / 180.)
! Create a geometry for all the discrete curves and surfaces in the mesh, by
! computing a parametrization for each one
call gmsh%model%mesh%createGeometry()
! Note that if a CAD model (e.g. as a STEP file, see `t20.f90') is available
! instead of an STL mesh, it is usually better to use that CAD model instead
! of the geometry created by reparametrizing the mesh% Indeed, CAD
! geometries will in general be more accurate, with smoother
! parametrizations, and will lead to more efficient and higher quality
! meshing. Discrete surface remeshing in Gmsh is optimized to handle dense
! STL meshes coming from e.g. imaging systems, where no CAD is available; it
! is less well suited for the poor quality STL triangulations (optimized for
! size, with e.g. very elongated triangles) that are usually generated by
! CAD tools for e.g. 3D printing.
! Create a volume from all the surfaces
call gmsh%model%getEntities(s, dim=2)
l = gmsh%model%geo%addSurfaceLoop(s(2, :))
ret = gmsh%model%geo%addVolume([l])
call gmsh%model%geo%synchronize()
! We specify element sizes imposed by a size field, just because we can :-)
f = gmsh%model%mesh%field%add("MathEval")
call gmsh%onelab%getNumber('Parameters/Apply funny mesh size field?', tmp)
if (int(tmp(1)) > 0) then
call gmsh%model%mesh%field%setString(f, "F", "2*Sin((x+y)/5) + 3")
else
call gmsh%model%mesh%field%setString(f, "F", "4")
end if
call gmsh%model%mesh%field%setAsBackgroundMesh(f)
call gmsh%model%mesh%generate(3)
call gmsh%write('t13.msh')
end subroutine createGeometryAndMesh
! Launch the GUI and handle the "check" event to recreate the geometry and mesh
! with new parameters if necessary:
logical function checkForEvent()
character(len=GMSH_API_MAX_STR_LEN), allocatable :: action(:)
checkForEvent = .false.
call gmsh%onelab%getString("ONELAB/Action", action)
if (size(action) > 0) then
if (trim(action(1)) == "check") then
call gmsh%onelab%setString("ONELAB/Action", [c_null_char])
call createGeometryAndMesh()
call gmsh%graphics%draw()
end if
end if
checkForEvent = .true.
end function checkForEvent
end program t13
|
