[PYTHON] vtkClipPolyData / DataSet Summary (Updated from time to time)

About vtkClipPolyData / DataSet

I will summarize Clip, which limits the area of the shape to be displayed based on the source shape.

When expressing the shape with vertices, lines, triangle like STL, vtkPolyData When expressing with an unstructured grid like ʻOpenFOAM, is it used as vtkDataSet`? I don't know the details yet

vtkClipPolyData class reference

https://vtk.org/doc/nightly/html/classvtkClipPolyData.html

vtkClipDataSet class reference

https://vtk.org/doc/nightly/html/classvtkClipDataSet.html

Check the function with paraview

Clip function

When ClipType is set to Plane, the display area is limited using the plane with the origin and normal.

By switching the Invert check, the displayed area can be reversed.

When the Crinkle clip is applied, the mesh contained in the plane retains its original shape.

Operation check with python

environment

python 3.7 vtk 8.1.2

Example of Clipping using the base code (plane)

)

import vtk

filename = "flange.stl"
reader = vtk.vtkSTLReader()
reader.SetFileName(filename)
reader.Update()

normal='y' # e.g. x,y,z,-x,-y,-z,X,Y,Z,-X,-Y,or -Z

NORMALS = {
    'x': [1, 0, 0],
    'y': [0, 1, 0],
    'z': [0, 0, 1],
    '-x': [-1, 0, 0],
    '-y': [0, -1, 0],
    '-z': [0, 0, -1],
}
normal = NORMALS[normal.lower()] # or e.g. [1.0/sqrt(2.0), 1.0/sqrt(2.0), 0]
origin = (0,0,0)
invert=True

plane = vtk.vtkPlane()
plane.SetNormal(normal)
plane.SetOrigin(origin)

alg = vtk.vtkClipPolyData()
alg.SetInputConnection(reader.GetOutputPort())

alg.SetClipFunction(plane)
alg.SetInsideOut(invert)
alg.Update()

# mapper
mapper = vtk.vtkCompositePolyDataMapper2()
mapper.SetInputConnection(alg.GetOutputPort()) #Set filter in mapper
mapper.SetScalarModeToUseCellFieldData() #Set for scalar data

# actor
actor = vtk.vtkActor()
actor.SetMapper(mapper)             #Set mapper for actor
actor.GetProperty().EdgeVisibilityOn()

# renderer
renderer = vtk.vtkRenderer()
renderer.AddActor(actor)            #Set actor in renderer

##Background color setting
renderer.GradientBackgroundOn()      #Set gradient background
renderer.SetBackground2(0.2,0.4,0.6) #Top color
renderer.SetBackground(1,1,1)        #Bottom color

#Window
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(renderer)         #Set renderer in Window
iren = vtk.vtkRenderWindowInteractor();
iren.SetRenderWindow(renWin);
renWin.SetSize(850, 850)
renWin.Render()
iren.Start();

SetClipFunction(vtkImplicitFunction e.g. vtkPlane)

Set the object that will be the source of Clip such as vtkPlane

List of inheritance destinations of vtkImplicitFunction https://vtk.org/doc/nightly/html/classvtkImplicitFunction.html

SetInsideOut(boolean)

Method to switch ʻInvert`

Can also be set with ʻInsideOutOn () or ʻInsideOutOff ()

Example of performing Clip using a quadrangle (Cube)

Use vtkBox to specify the coordinates of BoundingBox https://vtk.org/doc/nightly/html/classvtkBox.html

box = vtk.vtkBox()
box.SetXMin(0.0,-0.001,-0.01) # [xMin,yMin,zMin]
box.SetXMax(0.1,0.1,0.1)      # [xMax,yMax,zMax]

alg = vtk.vtkClipPolyData()
alg.SetInputConnection(reader.GetOutputPort())

alg.SetClipFunction(box)

Example for OpenFOAM

ʻOpenFOAM is an unstructured grid, so use vtkClipDataSet`

import vtk

filename = "case1.foam"
reader = vtk.vtkOpenFOAMReader()
reader.SetFileName(filename)
reader.CreateCellToPointOn()
reader.DecomposePolyhedraOn()
reader.EnableAllCellArrays()
reader.Update()

n_step = reader.GetTimeValues().GetNumberOfValues()
latest_time = reader.GetTimeValues().GetValue(n_step-1)
reader.UpdateTimeStep(latest_time)
reader.Update()


normal='y' # e.g. x,y,z,-x,-y,-z,X,Y,Z,-X,-Y,or -Z

NORMALS = {
    'x': [1, 0, 0],
    'y': [0, 1, 0],
    'z': [0, 0, 1],
    '-x': [-1, 0, 0],
    '-y': [0, -1, 0],
    '-z': [0, 0, -1],
}

normal = NORMALS[normal.lower()] # or e.g. [1.0/sqrt(2.0), 1.0/sqrt(2.0), 0]

origin = (0,0,0)
invert=False

plane = vtk.vtkPlane()
plane.SetNormal(normal)
plane.SetOrigin(origin)

alg = vtk.vtkClipDataSet()
alg.SetInputConnection(reader.GetOutputPort())
alg.SetClipFunction(plane)
alg.SetInsideOut(invert)
alg.Update()

filter = vtk.vtkGeometryFilter()
filter.SetInputConnection(alg.GetOutputPort())
# filter.SetInputConnection(reader.GetOutputPort()) //When clip Off
filter.Update()

# mapper
mapper = vtk.vtkCompositePolyDataMapper2()
mapper.SetInputConnection(filter.GetOutputPort()) #Set filter in mapper
mapper.SetScalarModeToUseCellFieldData() #Set for scalar data

# actor
actor = vtk.vtkActor()
actor.SetMapper(mapper)             #Set mapper for actor
actor.GetProperty().EdgeVisibilityOn()

# renderer
renderer = vtk.vtkRenderer()
renderer.AddActor(actor)            #Set actor in renderer

##Background color setting
renderer.GradientBackgroundOn()      #Set gradient background
renderer.SetBackground2(0.2,0.4,0.6) #Top color
renderer.SetBackground(1,1,1)        #Bottom color

#Window
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(renderer)         #Set renderer in Window
iren = vtk.vtkRenderWindowInteractor();
iren.SetRenderWindow(renWin);
renWin.SetSize(850, 850)
renWin.Render()
iren.Start();

Before Clip

After Clip