SmoothMeshgrid
VTKExamples/Python/PolyData/SmoothMeshgrid
Description
Create a terrain with regularly spaced points. The triangles are created manually. Then different types of smoothing filters are used to smooth the terrain.
Left : initial terrain, middle : vtkLoopSubdivisionFilter, right : vtkButterflySubdivisionFilter
*Contributed by Michka Popoff, with the help of Bill Lorensen and madz (madaramh).
Code
SmoothMeshgrid.py
#!/usr/bin/env python
import vtk
import random
import numpy
# Make a 32 x 32 grid
size = 32
# Define z values for the topography (random height)
topography = numpy.zeros([size, size])
for i in range(size):
for j in range(size):
topography[i][j] = random.randrange(0, 5)
# Define points, triangles and colors
colors = vtk.vtkUnsignedCharArray()
colors.SetNumberOfComponents(3)
points = vtk.vtkPoints()
triangles = vtk.vtkCellArray()
# Build the meshgrid manually
count = 0
for i in range(size-1):
for j in range(size-1):
z1 = topography[i][j]
z2 = topography[i][j+1]
z3 = topography[i+1][j]
# Triangle 1
points.InsertNextPoint(i, j, z1)
points.InsertNextPoint(i, (j+1), z2)
points.InsertNextPoint((i+1), j, z3)
triangle = vtk.vtkTriangle()
triangle.GetPointIds().SetId(0, count)
triangle.GetPointIds().SetId(1, count + 1)
triangle.GetPointIds().SetId(2, count + 2)
triangles.InsertNextCell(triangle)
z1 = topography[i][j+1]
z2 = topography[i+1][j+1]
z3 = topography[i+1][j]
# Triangle 2
points.InsertNextPoint(i, (j+1), z1)
points.InsertNextPoint((i+1), (j+1), z2)
points.InsertNextPoint((i+1), j, z3)
triangle = vtk.vtkTriangle()
triangle.GetPointIds().SetId(0, count + 3)
triangle.GetPointIds().SetId(1, count + 4)
triangle.GetPointIds().SetId(2, count + 5)
count += 6
triangles.InsertNextCell(triangle)
# Add some color
r = [int(i/float(size)*255),int(j/float(size)*255),0]
colors.InsertNextTupleValue(r)
colors.InsertNextTupleValue(r)
colors.InsertNextTupleValue(r)
colors.InsertNextTupleValue(r)
colors.InsertNextTupleValue(r)
colors.InsertNextTupleValue(r)
# Create a polydata object
trianglePolyData = vtk.vtkPolyData()
# Add the geometry and topology to the polydata
trianglePolyData.SetPoints(points)
trianglePolyData.GetPointData().SetScalars(colors)
trianglePolyData.SetPolys(triangles)
# Clean the polydata so that the edges are shared !
cleanPolyData = vtk.vtkCleanPolyData()
cleanPolyData.SetInputData(trianglePolyData)
# Use a filter to smooth the data (will add triangles and smooth)
# Use two different filters to show the difference
smooth_loop = vtk.vtkLoopSubdivisionFilter()
smooth_loop.SetNumberOfSubdivisions(3)
smooth_loop.SetInputConnection(cleanPolyData.GetOutputPort())
smooth_butterfly = vtk.vtkButterflySubdivisionFilter()
smooth_butterfly.SetNumberOfSubdivisions(3)
smooth_butterfly.SetInputConnection(cleanPolyData.GetOutputPort())
# Create a mapper and actor for initial dataset
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(trianglePolyData)
actor = vtk.vtkActor()
actor.SetMapper(mapper)
# Create a mapper and actor for smoothed dataset (vtkLoopSubdivisionFilter)
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(smooth_loop.GetOutputPort())
actor_loop = vtk.vtkActor()
actor_loop.SetMapper(mapper)
actor_loop.SetPosition(32, 0, 0)
# Create a mapper and actor for smoothed dataset (vtkButterflySubdivisionFilter)
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(smooth_butterfly.GetOutputPort())
actor_butterfly = vtk.vtkActor()
actor_butterfly.SetMapper(mapper)
actor_butterfly.SetPosition(64, 0, 0)
# Visualise
renderer = vtk.vtkRenderer()
renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)
renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)
# Add actors and render
renderer.AddActor(actor)
renderer.AddActor(actor_loop)
renderer.AddActor(actor_butterfly)
renderer.SetBackground(1, 1, 1) # Background color white
renderWindow.SetSize(800, 800)
renderWindow.Render()
renderWindowInteractor.Start()