Class: QgsMeshTransformVerticesByExpression

Transforms vertices of a mesh by expression.

Each coordinates are associated with an expression that can be defined with function returning the current coordinates (see setExpressions()):

  • $vertex_x

  • $vertex_y

  • $vertex_z

Example: Transposing a mesh and translate following axe X with a distance of 50 and increase the level of the mesh with an height of 80 when previous X coordinate is under 100 and de crease the level of 150 when X is under 100:

expressionX: “$vertex_y + 50” expressionY: “$vertex_x” expressionZ: “if( $vertex_x <= 100 , $vertex_z + 80 , $vertex_z - 150)”

Added in version 3.22.

Class Hierarchy

Inheritance diagram of qgis.core.QgsMeshTransformVerticesByExpression

Base classes

QgsMeshAdvancedEditing

Abstract class that can be derived to implement advanced editing on mesh.

Methods

calculate

Calculates the transformed vertices of the mesh layer, returns False if this leads to topological or geometrical errors.

setExpressions

Sets the expressions for the coordinates transformation.

setZFromTerrain

Sets if Z values for vertices should be obtained from project terrain, instead of expression.

transformedVertex

Returns the transformed vertex from its index vertexIndex for the mesh layer
class qgis.core.QgsMeshTransformVerticesByExpression[source]

Bases: QgsMeshAdvancedEditing

calculate(self, layer: QgsMeshLayer | None, project: QgsProject | None = None) → bool[source]

Calculates the transformed vertices of the mesh layer, returns False if this leads to topological or geometrical errors. The mesh layer must be in edit mode.

Note

This method does not apply new vertices to the mesh layer but only stores the calculated transformation that can be applied later with QgsMeshEditor.advancedEdit()

Parameters:

layer (Optional[QgsMeshLayer])

Added in version 3.44.

Parameters:

project (Optional[QgsProject] = None)

Return type:

bool

setExpressions(self, expressionX: str | None, expressionY: str | None, expressionZ: str | None)[source]

Sets the expressions for the coordinates transformation.

Note

Expressions are optional for each coordinate, the coordinate will not be transformed if the string is void.

Parameters:

  • expressionX (Optional[str])

  • expressionY (Optional[str])

  • expressionZ (Optional[str])

setZFromTerrain(self, enable: bool)[source]

Sets if Z values for vertices should be obtained from project terrain, instead of expression.

Note

If enable is True, the Z value of the vertex will be obtained from the terrain of the project. The optional parameter project is necessary for function calculate ( calculate() ).

Parameters:

enable (bool)

Added in version 3.44.

transformedVertex(self, layer: QgsMeshLayer | None, vertexIndex: int) → QgsPoint[source]

Returns the transformed vertex from its index vertexIndex for the mesh layer

If layer is not the same than the one used to make the calculation, this will create an undefined behavior

Parameters:
Return type:

QgsPoint