feat: add a mesh‑doctor action to compute a mesh’s Euler characteristic (#239)

* changed from surface to solid euler
---------
Co-authored-by: DENEL Bertrand <bertrand.denel@total.com>

Author: bd713

.github/workflows/README.md

@@ -6,7 +6,7 @@ This document explains the Continuous Integration (CI) setup for the geosPythonP
 
 The CI system consists of two main workflows:
 
-1. **`python-package.yml`** - Tests all Python packages individually
+1. **`python-package.yml`** - Tests all Python packages individually,
 2. **`test_geos_integration.yml`** - Tests integration with the GEOS simulation framework
 
 ## Workflow 1: Python Package Testing (`python-package.yml`)
@@ -485,4 +485,4 @@ When adding new Python packages or modifying existing ones:
 ## References
 
 - [GEOS Repository](https://github.com/GEOS-DEV/GEOS)
-- [GEOS Documentation](https://geosx-geosx.readthedocs-hosted.com/)
+- [GEOS Documentation](https://geosx-geosx.readthedocs-hosted.com/)

mesh-doctor/src/geos/mesh_doctor/actions/euler.py

@@ -0,0 +1,382 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright 2023-2024 TotalEnergies.
+"""Compute Solid Euler Characteristic for mesh files (3D elements only)."""
+
+from dataclasses import dataclass
+import vtk
+from tqdm import tqdm
+
+from geos.mesh_doctor.parsing.cliParsing import setupLogger
+from geos.mesh.io.vtkIO import readUnstructuredGrid
+
+
+@dataclass( frozen=True )
+class Options:
+    """Options for Euler characteristic computation."""
+    pass
+
+
+@dataclass( frozen=True )
+class Result:
+    """Result of solid Euler characteristic computation.
+
+    Attributes:
+        numVertices: Number of vertices (V) in 3D mesh
+        numEdges: Number of unique edges (E) in 3D mesh
+        numFaces: Number of unique faces (F) in 3D mesh
+        numCells: Number of 3D cells (C)
+        solidEulerCharacteristic: Solid Euler characteristic (chi = V - E + F - C)
+        num3dCells: Number of 3D volumetric cells in input
+        num2dCells: Number of 2D surface cells in input (ignored)
+        numOtherCells: Number of other cells in input
+        numBoundaryEdges: Number of boundary edges on surface
+        numNonManifoldEdges: Number of non-manifold edges on surface
+        numConnectedComponents: Number of disconnected 3D mesh regions
+    """
+    numVertices: int
+    numEdges: int
+    numFaces: int
+    numCells: int
+    solidEulerCharacteristic: int
+    num3dCells: int
+    num2dCells: int
+    numOtherCells: int
+    numBoundaryEdges: int
+    numNonManifoldEdges: int
+    numConnectedComponents: int
+
+
+def __countConnectedComponents( mesh: vtk.vtkUnstructuredGrid ) -> int:
+    """Count number of disconnected mesh components.
+
+    Args:
+        mesh: Input unstructured grid
+
+    Returns:
+        Number of disconnected regions
+    """
+    setupLogger.info( "Checking for disconnected 3D components..." )
+
+    connectivity = vtk.vtkConnectivityFilter()
+    connectivity.SetInputData( mesh )
+    connectivity.SetExtractionModeToAllRegions()
+    connectivity.ColorRegionsOn()
+    connectivity.Update()
+
+    numRegions = connectivity.GetNumberOfExtractedRegions()
+
+    setupLogger.info( f"Found {numRegions} disconnected 3D component(s)" )
+
+    return numRegions
+
+
+def __filter3dElements( mesh: vtk.vtkUnstructuredGrid ) -> tuple[ vtk.vtkUnstructuredGrid, int, int, int, bool ]:
+    """Filter only 3D volumetric elements from unstructured grid.
+
+    Removes 2D faces, 1D edges, and 0D vertices.
+
+    Args:
+        mesh: Input unstructured grid
+
+    Returns:
+        Tuple of (filtered_mesh, n_3d, n_2d, n_other, has_3d)
+    """
+    # Classify cells by dimension
+    cell3dIds = []
+    n3d = 0
+    n2d = 0
+    nOther = 0
+
+    setupLogger.info( "Classifying cell types..." )
+    for i in tqdm( range( mesh.GetNumberOfCells() ), desc="Scanning cells" ):
+        cell = mesh.GetCell( i )
+        cellDim = cell.GetCellDimension()
+
+        if cellDim == 3:
+            cell3dIds.append( i )
+            n3d += 1
+        elif cellDim == 2:
+            n2d += 1
+        else:
+            nOther += 1
+
+    setupLogger.info( "Cell type breakdown:" )
+    setupLogger.info( f"  3D volumetric cells: {n3d}" )
+    setupLogger.info( f"  2D surface cells:    {n2d}" )
+    setupLogger.info( f"  Other cells:         {nOther}" )
+
+    # Check if we have 3D cells
+    has3d = n3d > 0
+
+    if not has3d:
+        setupLogger.warning( "No 3D volumetric elements found!" )
+        setupLogger.warning( "This appears to be a pure surface mesh." )
+        setupLogger.warning( "Cannot compute solid Euler characteristic." )
+        return mesh, n3d, n2d, nOther, False
+
+    if n2d > 0:
+        setupLogger.info( f"Filtering out {n2d} 2D boundary cells..." )
+        setupLogger.info( f"Using only {n3d} volumetric elements" )
+
+    # Extract only 3D cells using vtkExtractCells
+    idList = vtk.vtkIdList()
+    for cellId in cell3dIds:
+        idList.InsertNextId( cellId )
+
+    extractor = vtk.vtkExtractCells()
+    extractor.SetInputData( mesh )
+    extractor.SetCellList( idList )
+    extractor.Update()
+
+    filteredMesh = extractor.GetOutput()
+
+    return filteredMesh, n3d, n2d, nOther, has3d
+
+
+def __countUniqueEdgesAndFaces( mesh: vtk.vtkUnstructuredGrid ) -> tuple[ int, int ]:
+    """Count unique edges and faces in 3D mesh (NumPy optimized).
+
+    Args:
+        mesh: 3D unstructured grid
+
+    Returns:
+        Tuple of (num_edges, num_faces)
+    """
+    setupLogger.info( "Counting unique edges and faces in 3D mesh..." )
+
+    try:
+        import numpy as np
+        use_numpy = True
+    except ImportError:
+        use_numpy = False
+
+    numCells = mesh.GetNumberOfCells()
+
+    if use_numpy:
+        # Use numpy for faster operations
+        edge_list = []
+        face_list = []
+
+        for i in tqdm( range( numCells ), desc="Processing cells", mininterval=1.0 ):
+
+            cell = mesh.GetCell( i )
+
+            # Edges
+            numEdges = cell.GetNumberOfEdges()
+            for edge_idx in range( numEdges ):
+                edge = cell.GetEdge( edge_idx )
+                p0 = edge.GetPointId( 0 )
+                p1 = edge.GetPointId( 1 )
+                edge_list.append( ( min( p0, p1 ), max( p0, p1 ) ) )
+
+            # Faces
+            numFaces = cell.GetNumberOfFaces()
+            for face_idx in range( numFaces ):
+                face = cell.GetFace( face_idx )
+                num_pts = face.GetNumberOfPoints()
+                point_ids = tuple( sorted( [ face.GetPointId( j ) for j in range( num_pts ) ] ) )
+                face_list.append( point_ids )
+
+        # Use numpy unique for deduplication (faster than set)
+        setupLogger.info( "  Deduplicating edges and faces..." )
+
+        # For edges: convert to array and use unique
+        edge_array = np.array( edge_list, dtype=np.int64 )
+        unique_edges = np.unique( edge_array, axis=0 )
+        num_edges = len( unique_edges )
+
+        # For faces: use set (numpy doesn't handle variable-length well)
+        num_faces = len( set( face_list ) )
+
+    else:
+        # Fallback to optimized set-based approach
+        edge_set = set()
+        face_set = set()
+
+        for i in tqdm( range( numCells ), desc="Processing cells", mininterval=0.5 ):
+            cell = mesh.GetCell( i )
+
+            numEdges = cell.GetNumberOfEdges()
+            for edge_idx in range( numEdges ):
+                edge = cell.GetEdge( edge_idx )
+                p0 = edge.GetPointId( 0 )
+                p1 = edge.GetPointId( 1 )
+                edge_set.add( ( min( p0, p1 ), max( p0, p1 ) ) )
+
+            numFaces = cell.GetNumberOfFaces()
+            for face_idx in range( numFaces ):
+                face = cell.GetFace( face_idx )
+                num_pts = face.GetNumberOfPoints()
+                face_set.add( tuple( sorted( [ face.GetPointId( j ) for j in range( num_pts ) ] ) ) )
+
+        num_edges = len( edge_set )
+        num_faces = len( face_set )
+
+    setupLogger.info( f"  Unique edges: {num_edges:,}" )
+    setupLogger.info( f"  Unique faces: {num_faces:,}" )
+
+    return num_edges, num_faces
+
+
+def __extractSurface( mesh: vtk.vtkUnstructuredGrid ) -> vtk.vtkPolyData:
+    """Extract surface from unstructured grid (3D elements only).
+
+    Args:
+        mesh: Input unstructured grid (3D elements)
+
+    Returns:
+        Surface as polydata
+    """
+    setupLogger.info( "Extracting boundary surface from 3D elements..." )
+    surfaceFilter = vtk.vtkDataSetSurfaceFilter()
+    surfaceFilter.SetInputData( mesh )
+    surfaceFilter.Update()
+    return surfaceFilter.GetOutput()
+
+
+def __checkMeshQuality( surface: vtk.vtkPolyData ) -> tuple[ int, int ]:
+    """Check for boundary edges and non-manifold features.
+
+    Args:
+        surface: Surface mesh
+
+    Returns:
+        Tuple of (boundary_edges, non_manifold_edges)
+    """
+    setupLogger.info( "Checking mesh quality..." )
+
+    # Count boundary edges
+    featureEdgesBoundary = vtk.vtkFeatureEdges()
+    featureEdgesBoundary.SetInputData( surface )
+    featureEdgesBoundary.BoundaryEdgesOn()
+    featureEdgesBoundary.ManifoldEdgesOff()
+    featureEdgesBoundary.NonManifoldEdgesOff()
+    featureEdgesBoundary.FeatureEdgesOff()
+    featureEdgesBoundary.Update()
+    boundaryEdges = featureEdgesBoundary.GetOutput().GetNumberOfCells()
+
+    # Count non-manifold edges
+    featureEdgesNm = vtk.vtkFeatureEdges()
+    featureEdgesNm.SetInputData( surface )
+    featureEdgesNm.BoundaryEdgesOff()
+    featureEdgesNm.ManifoldEdgesOff()
+    featureEdgesNm.NonManifoldEdgesOn()
+    featureEdgesNm.FeatureEdgesOff()
+    featureEdgesNm.Update()
+    nonManifoldEdges = featureEdgesNm.GetOutput().GetNumberOfCells()
+
+    return boundaryEdges, nonManifoldEdges
+
+
+def meshAction( mesh: vtk.vtkUnstructuredGrid, options: Options ) -> Result:
+    """Compute solid Euler characteristic for a mesh.
+
+    Only considers 3D volumetric elements. Computes chi_solid = V - E + F - C.
+
+    Args:
+        mesh: Input unstructured grid
+        options: Computation options
+
+    Returns:
+        Result with solid Euler characteristic and topology information
+    """
+    setupLogger.info( "Starting solid Euler characteristic computation..." )
+    setupLogger.info( f"Input mesh: {mesh.GetNumberOfPoints()} points, {mesh.GetNumberOfCells()} cells" )
+
+    # Filter to 3D elements only
+    mesh3d, n3d, n2d, nOther, has3d = __filter3dElements( mesh )
+
+    if not has3d:
+        raise RuntimeError( "Cannot compute solid Euler - no 3D cells found" )
+
+    # Count connected components
+    numComponents = __countConnectedComponents( mesh3d )
+
+    # Get basic counts
+    V = mesh3d.GetNumberOfPoints()
+    C = mesh3d.GetNumberOfCells()
+
+    # Count unique edges and faces in 3D mesh
+    E, F = __countUniqueEdgesAndFaces( mesh3d )
+
+    setupLogger.info( "Solid mesh topology:" )
+    setupLogger.info( f"  Vertices (V): {V:,}" )
+    setupLogger.info( f"  Edges    (E): {E:,}" )
+    setupLogger.info( f"  Faces    (F): {F:,}" )
+    setupLogger.info( f"  Cells    (C): {C:,}" )
+
+    # Calculate solid Euler characteristic
+    solidEuler = V - E + F - C
+
+    setupLogger.info( f"Solid Euler characteristic (chi = V - E + F - C): {solidEuler}" )
+
+    # Interpret result
+    setupLogger.info( "Topology interpretation:" )
+    setupLogger.info( f"  3D connected components: {numComponents}" )
+
+    if numComponents == 1:
+        if solidEuler == 1:
+            setupLogger.info( "  chi = 1: Contractible (solid ball topology)" )
+            setupLogger.info( "  VALID simple 3D region for simulation" )
+        elif solidEuler == 0:
+            setupLogger.warning( "  chi = 0: Solid torus (has through-hole)" )
+            setupLogger.warning( "  Verify this matches your domain geometry" )
+        elif solidEuler == 2:
+            setupLogger.warning( "  chi = 2: Hollow shell or internal cavity topology" )
+            setupLogger.warning( "  Expected chi = 1 for simple solid ball" )
+            setupLogger.warning( "  This suggests internal void or nested structure" )
+            setupLogger.warning( "  3D cells ARE connected (verified above) - verify intended" )
+        else:
+            setupLogger.warning( f"  chi = {solidEuler}: Unusual topology" )
+            setupLogger.warning( "  Verify mesh integrity" )
+    else:
+        setupLogger.error( f"  Mesh has {numComponents} disconnected 3D components!" )
+        setupLogger.error( "  This is NOT suitable for simulation without fixing" )
+
+    # Check mesh quality
+    surface = __extractSurface( mesh3d )
+    boundaryEdges, nonManifoldEdges = __checkMeshQuality( surface )
+
+    setupLogger.info( "Mesh quality:" )
+    setupLogger.info( f"  Boundary edges:     {boundaryEdges:,}" )
+    setupLogger.info( f"  Non-manifold edges: {nonManifoldEdges:,}" )
+
+    # Final validation
+    if numComponents == 1 and boundaryEdges == 0 and nonManifoldEdges == 0:
+        if solidEuler == 1:
+            setupLogger.info( "  Perfect: single connected volume, simple topology - READY!" )
+        else:
+            setupLogger.warning( f"  Connected volume but chi = {solidEuler}" )
+            setupLogger.warning( "  Verify internal features are intended" )
+    elif numComponents > 1:
+        setupLogger.error( "  Multiple disconnected regions - INVALID!" )
+    elif boundaryEdges > 0:
+        setupLogger.error( "  Open surface detected - INVALID!" )
+    elif nonManifoldEdges > 0:
+        setupLogger.error( "  Non-manifold geometry detected - INVALID!" )
+
+    return Result( numVertices=V,
+                   numEdges=E,
+                   numFaces=F,
+                   numCells=C,
+                   solidEulerCharacteristic=solidEuler,
+                   num3dCells=n3d,
+                   num2dCells=n2d,
+                   numOtherCells=nOther,
+                   numBoundaryEdges=boundaryEdges,
+                   numNonManifoldEdges=nonManifoldEdges,
+                   numConnectedComponents=numComponents )
+
+
+def action( vtuInputFile: str, options: Options ) -> Result:
+    """Compute solid Euler characteristic for a VTU file.
+
+    Args:
+        vtuInputFile: Path to input VTU file
+        options: Computation options
+
+    Returns:
+        Result with solid Euler characteristic and topology information
+    """
+    mesh = readUnstructuredGrid( vtuInputFile )
+    return meshAction( mesh, options )