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# ------------------------------------------------------------------------------
#
# Gmsh Julia tutorial 13
#
# Remeshing an STL file without an underlying CAD model
#
# ------------------------------------------------------------------------------
import gmsh
gmsh.initialize()
function createGeometryAndMesh()
# Clear all models and merge an STL mesh that we would like to remesh (from
# the parent directory):
gmsh.clear()
gmsh.merge(abspath(joinpath(@__DIR__, "..", "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):
angle = gmsh.onelab.getNumber("Parameters/Angle for surface detection")[1]
# 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:
forceParametrizablePatches = gmsh.onelab.getNumber(
"Parameters/Create surfaces guaranteed to be parametrizable")[1]
# For open surfaces include the boundary edges in the classification
# process:
includeBoundary = true
# Force curves to be split on given angle:
curveAngle = 180
gmsh.model.mesh.classifySurfaces(angle * pi / 180., includeBoundary,
forceParametrizablePatches,
curveAngle * pi / 180.)
# Create a geometry for all the discrete curves and surfaces in the mesh, by
# computing a parametrization for each one
gmsh.model.mesh.createGeometry()
# Note that if a CAD model (e.g. as a STEP file, see `t20.jl') 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
s = gmsh.model.getEntities(2)
l = gmsh.model.geo.addSurfaceLoop([e[2] for e in s])
gmsh.model.geo.addVolume([l])
gmsh.model.geo.synchronize()
# We specify element sizes imposed by a size field, just because we can :-)
f = gmsh.model.mesh.field.add("MathEval")
if gmsh.onelab.getNumber("Parameters/Apply funny mesh size field?")[1] != 0
gmsh.model.mesh.field.setString(f, "F", "2*Sin((x+y)/5) + 3")
else
gmsh.model.mesh.field.setString(f, "F", "4")
end
gmsh.model.mesh.field.setAsBackgroundMesh(f)
gmsh.model.mesh.generate(3)
gmsh.write("t13.msh")
end
# Create ONELAB parameters with remeshing options:
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:
createGeometryAndMesh()
# Launch the GUI and handle the "check" event to recreate the geometry and mesh
# with new parameters if necessary:
function checkForEvent()
action = gmsh.onelab.getString("ONELAB/Action")
if length(action) > 0 && action[1] == "check"
gmsh.onelab.setString("ONELAB/Action", [""])
createGeometryAndMesh()
gmsh.graphics.draw()
end
return true
end
if !("-nopopup" in ARGS)
gmsh.fltk.initialize()
while gmsh.fltk.isAvailable() == 1 && checkForEvent()
gmsh.fltk.wait()
end
end
gmsh.finalize()
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