Class: QgsTopologicalMesh

Wraps a QgsMesh to ensure the consistency of the mesh during editing and helps to access elements from other elements.

A topological face must:

• be convex

• be oriented counter-clockwise

• not share a unique vertex with another face

Added in version 3.22.

Methods

addFaces	Adds faces topologicFaces to the topologic mesh.
addFreeVertex	Adds a free vertex in the face, that is a vertex that is not included or linked with any faces.
addVertexInFace	Adds a vertex in the face with index faceIndex.
applyChanges	Applies the changes
canBeMerged	Returns True if faces separated by vertices with indexes vertexIndex1 and vertexIndex2 can be merged
canBeSplit	Returns True if face with index faceIndex can be split
changeXYValue	Changes the (X,Y) values of the vertices with indexes in vertices indexes with the values in newValues
changeZValue	Changes the Z values of the vertices with indexes in vertices indexes with the values in newValues
checkConsistency	Checks the consistency of the topological mesh and return False if there is a consistency issue
delaunayConditionForEdge	Check if Delaunay condition holds for given edge returns True if delaunay condition holds False otherwise
edgeCanBeFlipped	Returns True if the edge can be flipped (only available for edge shared by two faces with 3 vertices)
facesAroundVertex	Returns the indexes of faces that are around the vertex with index vertexIndex
facesCanBeAdded	Returns whether the faces can be added to the mesh
facesCanBeRemoved	Returns whether faces with index in faceIndexes can be removed The method an error object with type QgsMeshEditingError.NoError if the faces can be removed, otherwise returns the corresponding error
firstFaceLinked	Returns the index of the first face linked, returns -1 if it is a free vertex or out of range index
flipEdge	Flips edge (vertexIndex1, vertexIndex2) The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.
freeVerticesIndexes	Returns a list of vertices are not linked to any faces
insertVertexInFacesEdge	Inserts a vertex in the edge of face with index faceIndex at position .
isVertexFree	Returns whether the vertex is a free vertex
isVertexOnBoundary	Returns whether the vertex is on a boundary
merge	Merges faces separated by vertices with indexes vertexIndex1 and vertexIndex2 The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.
mesh	Returns a pointer to the wrapped mesh
neighborsOfFace	Returns the indexes of neighbor faces of the face with index faceIndex
reindex	Reindexes faces and vertices, after this operation, the topological mesh can't be edited anymore and only the method mesh can be used to access to the raw mesh.
removeFaces	Removes faces with index in faceIndexes.
removeVertexFillHole	Removes the vertex with index vertexIndex.
removeVertices	Removes all the vertices with index in the list vertices If vertices in linked with faces, the operation leads also to remove the faces without filling holes.
renumber	Renumbers the indexes of vertices and faces using the Reverse CutHill McKee Algorithm
reverseChanges	Reverses the changes
splitFace	Splits face with index faceIndex The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Static Methods

checkTopology	Checks the topology of the mesh mesh, if error occurs, this mesh can't be edited
counterClockwiseFaces	Checks the topology of the face and sets it counter clockwise if necessary
createTopologicalMesh	Creates a topologicaly consistent mesh with mesh, this static method modifies mesh to be topological consistent and return a QgsTopologicalMesh instance that contains and handles this mesh (does not take ownership).
vertexPositionInFace	Returns vertex position in face

class qgis.core.QgsTopologicalMesh

Bases: object

class Changes

Bases: object

Contains topological differences between two states of a topological mesh, only accessible from the QgsTopologicalMesh class.

Added in version 3.22.

addedVertices(self) → List[QgsPoint]

Returns the added vertices with this changes

Return type:

List[QgsPoint]

changedCoordinatesVerticesIndexes(self) → List[int]

Returns the indexes of vertices that have changed coordinates

Return type:

List[int]

clearChanges(self)

Clears all changes

isEmpty(self) → bool

Returns whether changes are empty, that there is nothing to change

Return type:

bool

nativeFacesIndexesGeometryChanged(self) → List[int]

Returns a list of the native face indexes that have a geometry changed

Return type:

List[int]

newVerticesXYValues(self) → List[QgsPointXY]

Returns the new (X,Y) values of vertices that have changed their coordinates

Return type:

List[QgsPointXY]

newVerticesZValues(self) → List[float]

Returns the new Z values of vertices that have changed their coordinates

Return type:

List[float]

oldVerticesXYValues(self) → List[QgsPointXY]

Returns the old (X,Y) values of vertices that have changed their coordinates

Return type:

List[QgsPointXY]

removedFaceIndexes(self) → List[int]

Returns the indexes of the faces that are removed with this changes

Return type:

List[int]

verticesToRemoveIndexes(self) → List[int]

Returns the indexes of vertices to remove

Return type:

List[int]

class TopologicalFaces

Bases: object

Contains independent faces and topological information about these faces.

This class supports unique shared vertices between faces.

Added in version 3.22.

clear(self)

Clears all data contained in the instance.

vertexToFace(self, vertexIndex: int) → int

Returns a face linked to the vertices with index vertexIndex

Parameters:

vertexIndex (int)

Return type:

int

addFaces(self, topologicFaces: QgsTopologicalMesh.TopologicalFaces) → QgsTopologicalMesh.Changes

Adds faces topologicFaces to the topologic mesh. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

topologicFaces (QgsTopologicalMesh.TopologicalFaces)

Return type:

QgsTopologicalMesh.Changes

addFreeVertex(self, vertex: QgsPoint) → QgsTopologicalMesh.Changes

Adds a free vertex in the face, that is a vertex that is not included or linked with any faces. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

vertex (QgsPoint)

Return type:

QgsTopologicalMesh.Changes

addVertexInFace(self, faceIndex: int, vertex: QgsPoint) → QgsTopologicalMesh.Changes

Adds a vertex in the face with index faceIndex. The including face is removed and new faces surrounding the added vertex are added. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

• faceIndex (int)

• vertex (QgsPoint)

Return type:

QgsTopologicalMesh.Changes

applyChanges(self, changes: QgsTopologicalMesh.Changes)

Applies the changes

Parameters:

changes (QgsTopologicalMesh.Changes)

canBeMerged(self, vertexIndex1: int, vertexIndex2: int) → bool

Returns True if faces separated by vertices with indexes vertexIndex1 and vertexIndex2 can be merged

Parameters:

• vertexIndex1 (int)

• vertexIndex2 (int)

Return type:

bool

canBeSplit(self, faceIndex: int) → bool

Returns True if face with index faceIndex can be split

Parameters:

faceIndex (int)

Return type:

bool

changeXYValue(self, verticesIndexes: Iterable[int], newValues: Iterable[QgsPointXY]) → QgsTopologicalMesh.Changes

Changes the (X,Y) values of the vertices with indexes in vertices indexes with the values in newValues

Parameters:

• verticesIndexes (Iterable[int])

• newValues (Iterable[QgsPointXY])

Return type:

QgsTopologicalMesh.Changes

changeZValue(self, verticesIndexes: Iterable[int], newValues: Iterable[float]) → QgsTopologicalMesh.Changes

Changes the Z values of the vertices with indexes in vertices indexes with the values in newValues

Parameters:

• verticesIndexes (Iterable[int])

• newValues (Iterable[float])

Return type:

QgsTopologicalMesh.Changes

checkConsistency(self) → QgsMeshEditingError

Checks the consistency of the topological mesh and return False if there is a consistency issue

Return type:

QgsMeshEditingError

static checkTopology(mesh: QgsMesh, maxVerticesPerFace: int) → QgsMeshEditingError

Checks the topology of the mesh mesh, if error occurs, this mesh can’t be edited

Parameters:

• mesh (QgsMesh)

• maxVerticesPerFace (int)

Return type:

QgsMeshEditingError

static counterClockwiseFaces(face: Iterable[int], mesh: QgsMesh | None) → QgsMeshEditingError

Checks the topology of the face and sets it counter clockwise if necessary

Parameters:

• face (Iterable[int])

• mesh (Optional[QgsMesh])

Return type:

QgsMeshEditingError

static createTopologicalMesh(mesh: QgsMesh | None, maxVerticesPerFace: int, error: QgsMeshEditingError) → QgsTopologicalMesh

Creates a topologicaly consistent mesh with mesh, this static method modifies mesh to be topological consistent and return a QgsTopologicalMesh instance that contains and handles this mesh (does not take ownership).

Parameters:

• mesh (Optional[QgsMesh])

• maxVerticesPerFace (int)

• error (QgsMeshEditingError)

Return type:

QgsTopologicalMesh

delaunayConditionForEdge(self, vertexIndex1: int, vertexIndex2: int) → bool

Check if Delaunay condition holds for given edge returns True if delaunay condition holds False otherwise

Added in version 3.42.

Parameters:

• vertexIndex1 (int)

• vertexIndex2 (int)

Return type:

bool

edgeCanBeFlipped(self, vertexIndex1: int, vertexIndex2: int) → bool

Returns True if the edge can be flipped (only available for edge shared by two faces with 3 vertices)

Parameters:

• vertexIndex1 (int)

• vertexIndex2 (int)

Return type:

bool

facesAroundVertex(self, vertexIndex: int) → List[int]

Returns the indexes of faces that are around the vertex with index vertexIndex

Parameters:

vertexIndex (int)

Return type:

List[int]

facesCanBeAdded(self, topologicalFaces: QgsTopologicalMesh.TopologicalFaces) → QgsMeshEditingError

Returns whether the faces can be added to the mesh

Parameters:

topologicalFaces (QgsTopologicalMesh.TopologicalFaces)

Return type:

QgsMeshEditingError

facesCanBeRemoved(self, facesIndexes: Iterable[int]) → QgsMeshEditingError

Returns whether faces with index in faceIndexes can be removed The method an error object with type QgsMeshEditingError.NoError if the faces can be removed, otherwise returns the corresponding error

Parameters:

facesIndexes (Iterable[int])

Return type:

QgsMeshEditingError

firstFaceLinked(self, vertexIndex: int) → int

Returns the index of the first face linked, returns -1 if it is a free vertex or out of range index

Parameters:

vertexIndex (int)

Return type:

int

flipEdge(self, vertexIndex1: int, vertexIndex2: int) → QgsTopologicalMesh.Changes

Flips edge (vertexIndex1, vertexIndex2) The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

• vertexIndex1 (int)

• vertexIndex2 (int)

Return type:

QgsTopologicalMesh.Changes

freeVerticesIndexes(self) → List[int]

Returns a list of vertices are not linked to any faces

Return type:

List[int]

insertVertexInFacesEdge(self, faceIndex: int, position: int, vertex: QgsPoint) → QgsTopologicalMesh.Changes

Inserts a vertex in the edge of face with index faceIndex at position . The faces that are on each side of the edge are removed and replaced by new faces constructed by a triangulation.

Parameters:

• faceIndex (int)

• position (int)

• vertex (QgsPoint)

Return type:

QgsTopologicalMesh.Changes

isVertexFree(self, vertexIndex: int) → bool

Returns whether the vertex is a free vertex

Parameters:

vertexIndex (int)

Return type:

bool

isVertexOnBoundary(self, vertexIndex: int) → bool

Returns whether the vertex is on a boundary

Parameters:

vertexIndex (int)

Return type:

bool

merge(self, vertexIndex1: int, vertexIndex2: int) → QgsTopologicalMesh.Changes

Merges faces separated by vertices with indexes vertexIndex1 and vertexIndex2 The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

• vertexIndex1 (int)

• vertexIndex2 (int)

Return type:

QgsTopologicalMesh.Changes

mesh(self) → QgsMesh | None

Returns a pointer to the wrapped mesh

Return type:

Optional[QgsMesh]

neighborsOfFace(self, faceIndex: int) → List[int]

Returns the indexes of neighbor faces of the face with index faceIndex

Parameters:

faceIndex (int)

Return type:

List[int]

reindex(self)

Reindexes faces and vertices, after this operation, the topological mesh can’t be edited anymore and only the method mesh can be used to access to the raw mesh.

removeFaces(self, facesIndexes: Iterable[int]) → QgsTopologicalMesh.Changes

Removes faces with index in faceIndexes. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

facesIndexes (Iterable[int])

Return type:

QgsTopologicalMesh.Changes

removeVertexFillHole(self, vertexIndex: int) → QgsTopologicalMesh.Changes

Removes the vertex with index vertexIndex. If the vertex in linked with faces, the operation leads also to remove the faces. In this case, the hole is filled by a triangulation. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

vertexIndex (int)

Return type:

QgsTopologicalMesh.Changes

removeVertices(self, vertices: Iterable[int]) → QgsTopologicalMesh.Changes

Removes all the vertices with index in the list vertices If vertices in linked with faces, the operation leads also to remove the faces without filling holes. The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

vertices (Iterable[int])

Return type:

QgsTopologicalMesh.Changes

renumber(self) → bool

Renumbers the indexes of vertices and faces using the Reverse CutHill McKee Algorithm

Return type:

bool

reverseChanges(self, changes: QgsTopologicalMesh.Changes)

Reverses the changes

Parameters:

changes (QgsTopologicalMesh.Changes)

splitFace(self, faceIndex: int) → QgsTopologicalMesh.Changes

Splits face with index faceIndex The method returns a instance of the class QgsTopologicalMesh.Change that can be used to reverse or reapply the operation.

Parameters:

faceIndex (int)

Return type:

QgsTopologicalMesh.Changes

static vertexPositionInFace(vertexIndex: int, face: Iterable[int]) → int

Returns vertex position in face

Parameters:

• vertexIndex (int)

• face (Iterable[int])

Return type:

int

static vertexPositionInFace(mesh: QgsMesh, vertexIndex: int, faceIndex: int) → int

Returns vertex position in face

Parameters:

• mesh (QgsMesh)

• vertexIndex (int)

• faceIndex (int)

Return type:

int