handling of meshes in 2d

docs/src/geo_and_meshes.md

@@ -34,3 +34,21 @@ more details on possible arguments):
 ```@example gmsh-sphere
 poly(view(msh,Ω);strokewidth=1,color=:lightgray, transparency=true)
 ```
+
+Two-dimensional meshes are very similar:
+
+```@example gmsh-disk
+    using Inti
+    using Gmsh
+    using GLMakie
+    gmsh.initialize()
+    gmsh.option.setNumber("General.Verbosity", 2)
+    gmsh.model.add("Disk")
+    gmsh.model.occ.addDisk(0,0,0,1,1)
+    gmsh.model.occ.synchronize()
+    gmsh.model.mesh.generate(2)
+    Ω   = Inti.gmsh_import_domain(;dim=2)
+    msh = Inti.gmsh_import_mesh(Ω;dim=2)
+    gmsh.finalize()
+    poly(view(msh,Ω);strokewidth=2)
+```

ext/IntiGmshExt.jl

@@ -134,7 +134,7 @@ function Inti.gmsh_import_mesh(Ω::Inti.Domain; dim=3)
     if dim == 3
         return msh
     elseif dim == 2
-        return convert_to_2d(msh)
+        return Inti._convert_to_2d(msh)
     else
         error("`dim` value must be `2` or `3`")
     end

src/mesh.jl

@@ -113,6 +113,38 @@ function Base.iterate(iter::ElementIterator{<:LagrangeElement,<:LagrangeMesh}, s
     return iter[state], state + 1
 end
 
+# convert a mesh to 2d by ignoring third component. Note that this also requires
+# converting various element types to their 2d counterpart. These are needed
+# because some meshers like gmsh always create three-dimensional objects, so we
+# must convert after importing the mesh
+function _convert_to_2d(mesh::LagrangeMesh{3,T}) where {T}
+    # create new dictionaries for elements and ent2tagsdict with 2d elements as keys
+    new_etype2mat = empty(mesh.etype2mat)
+    new_ent2tags  = empty(mesh.ent2tags)
+    for (E, tags) in mesh.etype2mat
+        E2d = _convert_to_2d(E)
+        new_etype2mat[E2d] = tags
+    end
+    for (ent, dict) in mesh.ent2tags
+        new_dict = empty(dict)
+        for (E, tags) in dict
+            E2d = _convert_to_2d(E)
+            new_dict[E2d] = tags
+        end
+        new_ent2tags[ent] = new_dict
+    end
+    # construct new 2d mesh
+    return LagrangeMesh{2,T}(
+                [x[1:2] for x in mesh.nodes],
+                new_etype2mat,
+                new_ent2tags
+            )
+end
+
+function _convert_to_2d(::Type{LagrangeElement{R,N,SVector{3,T}}}) where {R,N,T}
+    return LagrangeElement{R,N,SVector{2,T}}
+end
+
 """
     struct SubMesh{N,T} <: AbstractMesh{N,T}
 

test/gmsh_test.jl

@@ -3,6 +3,19 @@ using Gmsh
 using Test
 
 # for now that check that the code below does not error
+@test begin
+    gmsh.initialize()
+    gmsh.option.setNumber("General.Verbosity", 2)
+    gmsh.model.add("Disk")
+    gmsh.model.occ.addDisk(0,0,0,1,1)
+    gmsh.model.occ.synchronize()
+    gmsh.model.mesh.generate(2)
+    Ω   = Inti.gmsh_import_domain(;dim=2)
+    msh = Inti.gmsh_import_mesh(Ω;dim=2)
+    gmsh.finalize()
+    return true
+end
+
 @test begin
     gmsh.initialize()
     gmsh.option.setNumber("General.Verbosity", 2)