feat(meshGeneration): added mesh generation scripts and three res of spherical mesh

utils/meshGeneration/generateMesh.py

@@ -1,15 +1,25 @@
 import pygmsh
 import meshio
+import numpy as np
+from math import sqrt
 
 import argparse
 
-def generate_spherical_mesh(radius=1, meshSize=0.1):
-    with pygmsh.geo.Geometry() as geo:
-        # Create a spherical (ball) geometry centered at (0,0,0)
-        sphere = geo.add_ball([0, 0, 0], radius)
-        # Generate a 2D mesh (i.e. surface mesh) of the sphere
-        myMesh = geo.generate_mesh(dim=3)
-    return myMesh
+def mesh_size_callback(dim, tag, x, y, z, lc, a, b, k):
+    r = np.sqrt(x**2 + y**2 + z**2)
+    size = a + (b-a) * (1-np.exp(-k*r))
+    return size
+
+def generate_spherical_mesh(radius=1.0, coreRes = 0.1, outRes = 0.1, k = 2):
+    with pygmsh.occ.Geometry() as geom:
+        originPoint = geom.add_point([0.0, 0.0, 0.0], mesh_size=coreRes)
+        geom.add_ball([0.0, 0.0, 0.0], 1.0)
+
+        geom.set_mesh_size_callback(lambda dim, tag, x, y, z, lc: mesh_size_callback(dim, tag, x, y, z, lc, coreRes, outRes, k))
+        mesh = geom.generate_mesh(verbose=True)
+
+    return mesh
+
 
 def write_mfem_mesh(meshData, filename):
     meshio.write(filename, meshData, file_format='gmsh22')
@@ -17,8 +27,11 @@ def write_mfem_mesh(meshData, filename):
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Generate a spherical mesh')
     parser.add_argument('--radius', type=float, default=1.0, help='Radius of the sphere')
-    parser.add_argument('--meshSize', type=float, default=0.1, help='Mesh size')
+    parser.add_argument('--coreMeshRes', type=float, default=0.01, help='Core Mesh Resolution')
+    parser.add_argument('--outerMeshRes', type=float, default=0.1, help='Outer Mesh Resolution')
+    parser.add_argument('--k', type=float, default=2, help='Mesh size scaling factor')
+    parser.add_argument('--output', type=str, default='sphere.msh', help='Output file name')
     args = parser.parse_args()
 
-    meshData = generate_spherical_mesh(args.radius, args.meshSize)
-    write_mfem_mesh(meshData, 'sphere.msh')
+    meshData = generate_spherical_mesh(args.radius, args.coreMeshRes, args.outerMeshRes, args.k)
+    write_mfem_mesh(meshData, args.output)