NormalsDemo
vtk-examples/Python/Visualization/NormalsDemo
Description¶
This example demonstrates the generation of normals. The left image shows the orignal faceted model. The center image shows the model with generated normals, but no consideration for sharp features. The third image shows the model with a 30 degree feature angle and splitting on.
Theis example uses the src/Testing/Data/42400-IDGH.stl
dataset.
Info
See Figure 9-24 in Chapter 9 The VTK Textbook.
Other languages
See (Cxx)
Question
If you have a question about this example, please use the VTK Discourse Forum
Code¶
NormalsDemo.py
#!/usr/bin/env python
"""
"""
import vtk
def main():
colors = vtk.vtkNamedColors()
fileName = get_program_parameters()
polyData = ReadPolyData(fileName)
# A renderer.
renderer = vtk.vtkRenderer()
renderer.SetBackground(colors.GetColor3d("White"))
# Create background colors for each viewport.
backgroundColors = list()
backgroundColors.append(colors.GetColor3d("Cornsilk"))
backgroundColors.append(colors.GetColor3d("NavajoWhite"))
backgroundColors.append(colors.GetColor3d("Tan"))
# Create a renderer for each view port.
ren = list()
ren.append(vtk.vtkRenderer())
ren.append(vtk.vtkRenderer())
ren.append(vtk.vtkRenderer())
ren[0].SetViewport(0, 0, 1.0 / 3.0, 1) # Input
ren[1].SetViewport(1.0 / 3.0, 0, 2.0 / 3.0, 1) # Normals (no split)
ren[2].SetViewport(2.0 / 3.0, 0, 1, 1) # Normals (split)
# Shared camera.
camera = vtk.vtkCamera()
normals = vtk.vtkPolyDataNormals()
normals.SetInputData(polyData)
normals.SetFeatureAngle(30.0)
for i in range(0, 3):
if i == 0:
normals.ComputePointNormalsOff()
elif i == 1:
normals.ComputePointNormalsOn()
normals.SplittingOff()
else:
normals.ComputePointNormalsOn()
normals.SplittingOn()
normals.Update()
normalsPolyData = vtk.vtkPolyData()
normalsPolyData.DeepCopy(normals.GetOutput())
# mapper
mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(normalsPolyData)
mapper.ScalarVisibilityOff()
actor = vtk.vtkActor()
actor.SetMapper(mapper)
actor.GetProperty().SetDiffuseColor(colors.GetColor3d("Peacock"))
actor.GetProperty().SetDiffuse(.7)
actor.GetProperty().SetSpecularPower(20)
actor.GetProperty().SetSpecular(.5)
# add the actor
ren[i].SetBackground(backgroundColors[i])
ren[i].SetActiveCamera(camera)
ren[i].AddActor(actor)
# Render window.
renwin = vtk.vtkRenderWindow()
renwin.AddRenderer(ren[0])
renwin.AddRenderer(ren[1])
renwin.AddRenderer(ren[2])
renwin.SetWindowName('NormalsDemo')
# An interactor.
interactor = vtk.vtkRenderWindowInteractor()
interactor.SetRenderWindow(renwin)
renwin.SetSize(900, 300)
ren[0].GetActiveCamera().SetFocalPoint(0, 0, 0)
ren[0].GetActiveCamera().SetPosition(1, 0, 0)
ren[0].GetActiveCamera().SetViewUp(0, 0, -1)
ren[0].ResetCamera()
ren[0].GetActiveCamera().Azimuth(120)
ren[0].GetActiveCamera().Elevation(30)
ren[0].GetActiveCamera().Dolly(1.1)
ren[0].ResetCameraClippingRange()
renwin.Render()
ren[0].ResetCamera()
renwin.Render()
# Start.
interactor.Initialize()
interactor.Start()
def get_program_parameters():
import argparse
description = 'Surface normal generation.'
epilogue = '''
(a) Faceted model without normals.
(b) Polygons must be consistently oriented to accurately compute normals.
(c) Sharp edges are poorly represented using shared normals as shown on the corners of this model.
(d) Normal generation with sharp edges split.
'''
parser = argparse.ArgumentParser(description=description, epilog=epilogue,
formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument('filename1', help='42400-IDGH.stl.')
args = parser.parse_args()
return args.filename1
def ReadPolyData(file_name):
import os
path, extension = os.path.splitext(file_name)
extension = extension.lower()
if extension == ".ply":
reader = vtk.vtkPLYReader()
reader.SetFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
elif extension == ".vtp":
reader = vtk.vtkXMLpoly_dataReader()
reader.SetFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
elif extension == ".obj":
reader = vtk.vtkOBJReader()
reader.SetFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
elif extension == ".stl":
reader = vtk.vtkSTLReader()
reader.SetFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
elif extension == ".vtk":
reader = vtk.vtkpoly_dataReader()
reader.SetFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
elif extension == ".g":
reader = vtk.vtkBYUReader()
reader.SetGeometryFileName(file_name)
reader.Update()
poly_data = reader.GetOutput()
else:
# Return a None if the extension is unknown.
poly_data = None
return poly_data
if __name__ == '__main__':
main()