CellPicking

#!/usr/bin/env python3

# noinspection PyUnresolvedReferences
import vtkmodules.vtkRenderingOpenGL2
from vtkmodules.vtkCommonColor import vtkNamedColors
from vtkmodules.vtkCommonCore import vtkIdTypeArray
from vtkmodules.vtkCommonDataModel import (
    vtkSelection,
    vtkSelectionNode,
    vtkUnstructuredGrid
)
from vtkmodules.vtkFiltersCore import vtkTriangleFilter
from vtkmodules.vtkFiltersExtraction import vtkExtractSelection
from vtkmodules.vtkFiltersSources import vtkPlaneSource
from vtkmodules.vtkInteractionStyle import vtkInteractorStyleTrackballCamera
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkCellPicker,
    vtkDataSetMapper,
    vtkPolyDataMapper,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
    vtkRenderer
)


class MouseInteractorStyle(vtkInteractorStyleTrackballCamera):
    """
    Catch mouse events.
    """

    def __init__(self, data):
        super().__init__()

        self.AddObserver('LeftButtonPressEvent', self.left_button_press_event)

        self.data = data
        self.selected_mapper = vtkDataSetMapper()
        self.selected_actor = vtkActor(mapper=self.selected_mapper)

    def left_button_press_event(self, obj, event):
        colors = vtkNamedColors()

        # Get the location of the click (in window coordinates)
        pos = self.interactor.GetEventPosition()

        picker = vtkCellPicker(tolerance=0.0005)

        # Pick from this location.
        picker.Pick(pos[0], pos[1], 0, self.default_renderer)

        world_position = picker.pick_position
        print(f'Cell id is: {picker.cell_id}')

        if picker.cell_id != -1:
            print(f'Pick position is: ({world_position[0]:.6g}, {world_position[1]:.6g}, {world_position[2]:.6g})')

            ids = vtkIdTypeArray(number_of_components=1)
            ids.InsertNextValue(picker.cell_id)

            selection_node = vtkSelectionNode(field_type=vtkSelectionNode.CELL,
                                              content_type=vtkSelectionNode.INDICES,
                                              selection_list=ids)

            selection = vtkSelection()
            selection.AddNode(selection_node)

            extract_selection = vtkExtractSelection()
            extract_selection.SetInputData(0, self.data)
            extract_selection.SetInputData(1, selection)
            extract_selection.update()

            # In selection
            selected = vtkUnstructuredGrid()
            selected.ShallowCopy(extract_selection.output)

            print(f'Number of points in the selection: {selected.number_of_points}')
            print(f'Number of cells in the selection : {selected.number_of_cells}')

            selected >> self.selected_mapper
            self.selected_actor.property.edge_visibility = True
            self.selected_actor.property.color = colors.GetColor3d('Tomato')
            self.selected_actor.property.line_width = 3

            self.interactor.render_window.renderers.first_renderer.AddActor(self.selected_actor)

        # Forward events
        self.OnLeftButtonDown()


def main(argv):
    colors = vtkNamedColors()

    plane_source = vtkPlaneSource()

    triangle_filter = vtkTriangleFilter()

    mapper = vtkPolyDataMapper()
    plane_source >> triangle_filter >> mapper

    actor = vtkActor(mapper=mapper)
    actor.property.color = colors.GetColor3d('SeaGreen')

    renderer = vtkRenderer(background=colors.GetColor3d('PaleTurquoise'))
    ren_win = vtkRenderWindow(window_name='CellPicking')
    ren_win.AddRenderer(renderer)
    iren = vtkRenderWindowInteractor()
    iren.render_window = ren_win

    renderer.AddActor(actor)

    # Add the custom style.
    style = MouseInteractorStyle(triangle_filter.output)
    style.default_renderer = renderer
    iren.interactor_style = style

    ren_win.Render()
    iren.Initialize()
    iren.Start()


if __name__ == '__main__':
    import sys

    main(sys.argv)