Add python modules that uses the CGAL binding

examples/meshing/CGAL/README.txt

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+This folder presents two simple modules using CGAL bindings allowing for easy tetrahedric mesh generation from either a polyhedron of its surface or a point cloud (using a convexe hull).
+
+You can you this through the two mains (mesh_from_point_cloud_using_convex_hull.py and mesh_from_polyhedron.py) through command line (use -h for more information) or simply use the cgal_utils.py module if you want to build new scripts upon this work. The most important class being CGAL_Mesh_3_IO_Util heping to deal with the CGal data structure and use they results as numpy array. To see usage example, see mesh_from_polyhedron.py:CGAL_Mesh_from_polyhedron().
+
+Those scripts are here to replace the components MeshGenerationFromPolyhedron and TriangularConvexHull3D from the CGALPLugin https://github.com/sofa-framework/CGALPlugin

examples/meshing/CGAL/cgal_utils.py

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+from CGAL.CGAL_Polyhedron_3 import Polyhedron_3, Polyhedron_modifier
+from CGAL.CGAL_Mesh_3 import Mesh_3_Complex_3_in_triangulation_3
+from CGAL.CGAL_Mesh_3 import Polyhedral_mesh_domain_3
+from CGAL.CGAL_Mesh_3 import Mesh_3_parameters
+from CGAL.CGAL_Mesh_3 import Default_mesh_criteria
+from CGAL.CGAL_Kernel import Point_3
+from CGAL import CGAL_Mesh_3
+
+import numpy as np
+import dataclasses
+from typing import List, Optional
+
+from enum import Enum
+from pathlib import Path
+
+import time
+
+from vtkmodules.vtkIOGeometry import (
+     vtkBYUReader,
+     vtkOBJReader,
+     vtkSTLReader
+ )
+from vtkmodules.vtkIOLegacy import vtkPolyDataReader
+from vtkmodules.vtkIOPLY import vtkPLYReader
+from vtkmodules.vtkIOXML import vtkXMLPolyDataReader
+
+import vtk
+from vtk.util import numpy_support
+from vtk.numpy_interface import algorithms as algs
+
+timestamp = {}
+
+def tic(hash = 0):
+    global timestamp
+    timestamp[hash] = time.time_ns()
+
+def toc(hash = 0):
+    global timestamp
+    return f"{((time.time_ns() - timestamp[hash])/1000000):.3f} miliseconds"
+
+
+def ReadPolyData(file_name):
+    #FROM Vtk examples https://examples.vtk.org/site/Python/Snippets/ReadPolyData/
+
+    valid_suffixes = ['.g', '.obj', '.stl', '.ply', '.vtk', '.vtp']
+
+    path = Path(file_name)
+    if path.suffix:
+        ext = path.suffix.lower()
+    if path.suffix not in valid_suffixes:
+        print(f'No reader for this file suffix: {ext}')
+        return None
+    else:
+        if ext == ".ply":
+            reader = vtkPLYReader()
+            reader.SetFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+        elif ext == ".vtp":
+            reader = vtkXMLPolyDataReader()
+            reader.SetFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+        elif ext == ".obj":
+            reader = vtkOBJReader()
+            reader.SetFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+        elif ext == ".stl":
+            reader = vtkSTLReader()
+            reader.SetFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+        elif ext == ".vtk":
+            reader = vtkPolyDataReader()
+            reader.SetFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+        elif ext == ".g":
+            reader = vtkBYUReader()
+            reader.SetGeometryFileName(file_name)
+            reader.Update()
+            poly_data = reader.GetOutput()
+
+        return poly_data
+
+
+class CGAL_Mesh_3_IO_Util(object):
+
+    points    : np.array
+    triangles : np.array
+    tetras    : np.array
+
+    class Elem(Enum):
+        POINTS = 1
+        TRIANGLES = 3
+        TETRA = 4
+
+    def __init__(self,mesh):
+        self.mesh = mesh
+
+    def extract(self, elems : list[Elem]):
+
+        print(f"Extracting data into numpy objects...")
+        tic()
+
+        for elem in elems:
+            vnbe = {}
+            match elem:
+                case CGAL_Mesh_3_IO_Util.Elem.TRIANGLES:
+                    for elemf in self.mesh.facets():
+                        for i in range(3):
+                            if not elemf.vertex in vnbe:
+                                vnbe[elemf.vertex(i)] = 1 
+                            else:
+                                vnbe[elem.vertex(i)] += 1 
+                case CGAL_Mesh_3_IO_Util.Elem.TETRA:
+                    for elemc in self.mesh.cells():
+                        for i in range(4):
+                            if not elemc.vertex in vnbe:
+                                vnbe[elemc.vertex(i)] = 1 
+                            else:
+                                vnbe[elemc.vertex(i)] += 1 
+
+
+            V = {}
+            it = 0
+            for vertice in self.mesh.triangulation().finite_vertices():
+                if vertice in vnbe:
+                    V[vertice] = it
+                    it += 1 
+
+            if CGAL_Mesh_3_IO_Util.Elem.POINTS in elems:
+                self.points = np.empty((len(V),3))
+                id = 0
+                for key in V.keys():
+                    self.points[id][:] = [self.mesh.triangulation().point(key).x(), self.mesh.triangulation().point(key).y(), self.mesh.triangulation().point(key).z()]
+                    id+=1
+
+            match elem:
+                case CGAL_Mesh_3_IO_Util.Elem.TRIANGLES:
+                    self.triangles = np.empty((self.mesh.number_of_facets(),3), dtype=np.int32)
+                    id = 0
+                    for elemt in self.mesh.facets():
+                        self.triangles[id][:]  = [V[elemt.vertex(0)],V[elemt.vertex(1)],V[elemt.vertex(2)]]
+                        id+= 1 
+                case CGAL_Mesh_3_IO_Util.Elem.TETRA:
+                    self.tetras = np.empty((self.mesh.number_of_cells(),4), dtype=np.int32)
+                    id = 0
+                    for elemc in self.mesh.cells():
+                        self.tetras[id][:]  = [V[elemc.vertex(0)],V[elemc.vertex(1)],V[elemc.vertex(2)], V[elemc.vertex(3)]]
+                        id += 1
+        print(f"Done ! Took {toc()}")
+        if CGAL_Mesh_3_IO_Util.Elem.TRIANGLES in elems:
+            print(f"Extracted {self.points.shape[0]} points and {self.triangles.shape[0]} triangles")
+        if CGAL_Mesh_3_IO_Util.Elem.TETRA in elems:
+            print(f"Extracted {self.points.shape[0]} points and {self.tetras.shape[0]} tetras")
+
+
+
+    def write_out(self, filename):
+        path = Path(filename)
+        ext = path.suffix.lower()
+        if ext != ".vtk" and ext != ".vtu":
+            print("Only vtk or vtu extension are suported")
+            return
+
+        if (not "tetras"  in self.__dict__) and ext == ".vtu":
+            print("VTU only supported for tetrahedral meshes. Use vtk instead")
+            return
+
+        print(f"Saving into {filename}...")
+        tic()
+
+        if "tetras"  in self.__dict__:
+            ugrid = vtk.vtkUnstructuredGrid()
+        else:
+            ugrid = vtk.vtkPolyData()
+
+        vtk_points = vtk.vtkPoints()
+        vtk_points.SetData(numpy_support.numpy_to_vtk(self.points, deep=True))
+        ugrid.SetPoints(vtk_points)
+
+
+        if "triangles" in self.__dict__:
+            for triangle in self.triangles:
+                vtkTriangleObj = vtk.vtkTriangle()
+                vtkTriangleObj.GetPointIds().SetId(0,triangle[0])
+                vtkTriangleObj.GetPointIds().SetId(1,triangle[1])
+                vtkTriangleObj.GetPointIds().SetId(2,triangle[2])
+                ugrid.InsertNextCell(vtkTriangleObj.GetCellType(), vtkTriangleObj.GetPointIds())
+        if "tetras"  in self.__dict__:
+            for tetra in self.tetras:
+                vtkTetraObj = vtk.vtkTetra()
+                vtkTetraObj.GetPointIds().SetId(0,tetra[0])
+                vtkTetraObj.GetPointIds().SetId(1,tetra[1])
+                vtkTetraObj.GetPointIds().SetId(2,tetra[2])
+                vtkTetraObj.GetPointIds().SetId(3,tetra[3])
+                ugrid.InsertNextCell(vtkTetraObj.GetCellType(), vtkTetraObj.GetPointIds())
+
+
+        if "tetras"  in self.__dict__:
+            writer = vtk.vtkUnstructuredGridWriter()
+        else:
+            writer = vtk.vtkPolyDataWriter()
+        writer.SetFileVersion(42)
+        writer.SetInputData(ugrid)
+        writer.SetFileName(filename)
+        writer.Write()
+        print(f"Done ! Took {toc()}")
+
+
+
+
+
+class CGAL_Mesh_from(object):
+
+    class Refiner(Enum):
+        NONE = 0
+        LLOYD = 1
+        ODT = 3
+        PERTURB = 4
+
+    @dataclasses.dataclass
+    class Refiner_input():
+        refiner_type : Enum
+
+        time_limit : Optional[float] = 20.0         #(ALL)              to set up, in seconds, a CPU time limit after which the optimization process is stopped. This time is measured using CGAL::Real_timer. 0 means that there is no time limit. 
+        max_iteration_number : Optional[int] = 200  #(LLOYD & ODT only) limit on the number of performed iterations. 0 means that there is no limit on the number of performed iterations.   
+        convergence : Optional[int] = 0.0           #(LLOYD & ODT only) threshold ratio of stopping criterion based on convergence: the optimization process is stopped when at the last iteration the displacement of any vertex is less than a given fraction of the length of the shortest edge incident to that vertex.
+        free_bound : Optional[bool] = False         #(LLOYD & ODT only) designed to reduce running time of each optimization iteration. Any vertex that has a displacement less than a given fraction of the length of its shortest incident edge, is frozen (i.e. is not relocated). The parameter freeze_bound gives the threshold ratio. If it is set to 0, freezing of vertices is disabled. 
+        silver_bound : Optional[bool] = False       #(PERTURB only)     is designed to give, in degrees, a targeted lower bound on dihedral angles of mesh cells. The exudation process considers in turn all the mesh cells that have a smallest dihedral angle less than sliver_bound and tries to make them disappear by weighting their vertices. The optimization process stops when every cell in the mesh achieves this quality. The default value is 0 and means that there is no targeted bound: the exuder then runs as long as it can improve the smallest dihedral angles of the set of cells incident to some vertices. 
+
+
+    IOUtil : CGAL_Mesh_3_IO_Util
+
+    def __init__(self):
+        pass
+
+    def generate(self):
+        pass
+
+
+    def __getattr__(self, name):
+        match name:
+            case "points":
+                return self.IOUtil.points
+            case "triangles":
+                return self.IOUtil.triangles
+            case "tetras":
+                return self.IOUtil.tetras
+            case _:
+                if name in self.__dict__:
+                    return self.__dict__[name]
+                else:
+                    raise AttributeError()
+
+
+