Add TransformedMesh (#663)

* Add 'TransformedMesh'

* Update tests

* Fix tests

src/Meshes.jl

@@ -280,6 +280,7 @@ export
   RectilinearGrid,
   StructuredGrid,
   SimpleMesh,
+  TransformedMesh,
   vertex,
   vertices,
   nvertices,

src/mesh.jl

@@ -208,6 +208,7 @@ include("mesh/cartesiangrid.jl")
 include("mesh/rectilineargrid.jl")
 include("mesh/structuredgrid.jl")
 include("mesh/simplemesh.jl")
+include("mesh/transformedmesh.jl")
 
 # ------------
 # CONVERSIONS

src/mesh/transformedmesh.jl

@@ -0,0 +1,17 @@
+# ------------------------------------------------------------------
+# Licensed under the MIT License. See LICENSE in the project root.
+# ------------------------------------------------------------------
+
+"""
+    TransformedMesh(mesh, transform)
+
+Lazy representation of a geometric `transform` applied to a `mesh`.
+"""
+struct TransformedMesh{Dim,T,M<:Mesh{Dim,T},TR<:Transform} <: Mesh{Dim,T}
+  mesh::M
+  transform::TR
+end
+
+topology(m::TransformedMesh) = topology(m.mesh)
+
+vertex(m::TransformedMesh, ind::Int) = m.transform(vertex(m.mesh, ind))

test/mesh.jl

@@ -441,4 +441,21 @@
         └─ Triangle(3, 1, 5)"""
     end
   end
+
+  @testset "TransformedMesh" begin
+    grid = CartesianGrid{T}(10, 10)
+    rgrid = convert(RectilinearGrid, grid)
+    sgrid = convert(StructuredGrid, grid)
+    mesh = convert(SimpleMesh, grid)
+    trans = Identity()
+    @test TransformedMesh(grid, trans) == grid
+    @test TransformedMesh(rgrid, trans) == rgrid
+    @test TransformedMesh(sgrid, trans) == sgrid
+    @test TransformedMesh(mesh, trans) == mesh
+    trans = Translate(T(10), T(10)) → Translate(T(-10), T(-10))
+    @test TransformedMesh(grid, trans) == grid
+    @test TransformedMesh(rgrid, trans) == rgrid
+    @test TransformedMesh(sgrid, trans) == sgrid
+    @test TransformedMesh(mesh, trans) == mesh
+  end
 end

test/runtests.jl

@@ -13,6 +13,8 @@ using Rotations
 using Test, Random
 using ReferenceTests, ImageIO
 
+using TransformsBase: Identity, →
+
 import TransformsBase as TB
 import CairoMakie as Mke