CreateESGrid

#!/usr/bin/env python3

import numpy as np

# noinspection PyUnresolvedReferences
import vtkmodules.vtkRenderingOpenGL2
from vtkmodules.vtkCommonColor import vtkNamedColors
from vtkmodules.vtkCommonCore import vtkPoints
from vtkmodules.vtkCommonDataModel import (
    vtkCellArray,
    vtkExplicitStructuredGrid
)
from vtkmodules.vtkFiltersCore import (
    vtkExplicitStructuredGridToUnstructuredGrid,
    vtkUnstructuredGridToExplicitStructuredGrid
)
from vtkmodules.vtkInteractionStyle import vtkInteractorStyleRubberBandPick
from vtkmodules.vtkRenderingCore import (
    vtkActor,
    vtkDataSetMapper,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
    vtkRenderer
)


def create_explicit_structured_grid(dimensions, spacing=(1, 1, 1)):
    """Create an explicit structured grid.

    Parameters
    ----------
    dimensions : tuple(int, int, int)
        The number of points in the (I, J, K) directions.
    spacing : tuple(int, int, int)
        The spacing between points in the (I, J, K) directions.

    Returns
    -------
    grid : vtkExplicitStructuredGrid
        An explicit structured grid.

    """
    ni, nj, nk = dimensions
    si, sj, sk = spacing

    points = vtkPoints()
    for z in range(0, nk * sk, sk):
        for y in range(0, nj * sj, sj):
            for x in range(0, ni * si, si):
                points.InsertNextPoint((x, y, z))

    cells = vtkCellArray()
    for k in range(0, nk - 1):
        for j in range(0, nj - 1):
            for i in range(0, ni - 1):
                multi_index = ([i, i + 1, i + 1, i, i, i + 1, i + 1, i],
                               [j, j, j + 1, j + 1, j, j, j + 1, j + 1],
                               [k, k, k, k, k + 1, k + 1, k + 1, k + 1])
                pts = np.ravel_multi_index(multi_index, dimensions, order='F')
                cells.InsertNextCell(8, pts)

    return vtkExplicitStructuredGrid(dimensions=(ni, nj, nk), points=points, cells=cells)


def convert_to_unstructured_grid(grid):
    """Convert explicit structured grid to unstructured grid.

    Parameters
    ----------
    grid : vtkExplicitStructuredGrid
        An explicit structured grid.

    Returns
    -------
    vtkUnstructuredGrid
        An unstructured grid.

    """
    converter = vtkExplicitStructuredGridToUnstructuredGrid()
    return (grid >> converter).update().output


def convert_to_explicit_structured_grid(grid):
    """Convert unstructured grid to explicit structured grid.

    Parameters
    ----------
    grid : UnstructuredGrid
        An unstructured grid.

    Returns
    -------
    vtkExplicitStructuredGrid
        An explicit structured grid. The ``'BLOCK_I'``, ``'BLOCK_J'`` and
        ``'BLOCK_K'`` cell arrays are required.

    """
    converter = vtkUnstructuredGridToExplicitStructuredGrid()
    input_arrays_to_process = ((0, 0, 0, 1, 'BLOCK_I'), (1, 0, 0, 1, 'BLOCK_J'), (2, 0, 0, 1, 'BLOCK_K'))
    for input_array in input_arrays_to_process:
        converter.SetInputArrayToProcess(*input_array)
    return grid >> converter


def main():
    grid = create_explicit_structured_grid((5, 6, 7), (20, 10, 1))
    grid = convert_to_unstructured_grid(grid)
    grid = convert_to_explicit_structured_grid(grid)

    colors = vtkNamedColors()

    mapper = vtkDataSetMapper()

    actor = vtkActor(mapper=mapper)
    actor.property.edge_visibility = True
    actor.property.lighting = False
    actor.property.color = colors.GetColor3d('Seashell')

    grid >> mapper

    renderer = vtkRenderer(background=colors.GetColor3d('DarkSlateGray'))
    renderer.AddActor(actor)

    window = vtkRenderWindow(size=(1024, 768), window_name='CreateESGrid')
    window.AddRenderer(renderer)
    window.Render()

    camera = renderer.active_camera
    camera.position = (8.383354, -72.468670, 94.262605)
    camera.focal_point = (42.295234, 21.111537, -0.863606)
    camera.view_up = (0.152863, 0.676710, 0.720206)
    camera.distance = 137.681759
    camera.clipping_range = (78.173985, 211.583658)

    interactor = vtkRenderWindowInteractor()
    interactor.render_window = window
    interactor.interactor_style = vtkInteractorStyleRubberBandPick()
    window.Render()
    interactor.Start()


if __name__ == '__main__':
    main()