CutWithScalars根据标量利用vtkContourFilter得到等值线

一：主要的知识点

1、说明

本文只是教程内容的一小段，因博客字数限制，故进行拆分。主教程链接：vtk教程------逐行解析官网所有Python示例-CSDN博客

2、知识点纪要

本段代码主要涉及的有①vtkContour的用法，②点在平面哪一个方向的判定方法

二：代码及注释

import vtkmodules.vtkRenderingOpenGL2
from vtkmodules.vtkCommonColor import vtkNamedColors
from vtkmodules.vtkCommonCore import vtkDoubleArray
from vtkmodules.vtkCommonDataModel import vtkPlane
from vtkmodules.vtkFiltersCore import vtkContourFilter, vtkMarchingCubes
from vtkmodules.vtkIOXML import vtkXMLPolyDataReader
from vtkmodules.vtkRenderingCore import vtkActor, vtkRenderer, vtkRenderWindow, vtkPolyDataMapper, \
    vtkRenderWindowInteractor
 
 
def main():
    file_name = "Data/Torso.vtp"
    num_of_cuts = 20
 
    colors = vtkNamedColors()
 
    reader = vtkXMLPolyDataReader()
    reader.SetFileName(file_name)
    reader.Update()
 
    bounds = reader.GetOutput().GetBounds()
 
    plane = vtkPlane()
    plane.SetOrigin((bounds[0] + bounds[1]) / 2,
                    (bounds[2] + bounds[3]) / 2,
                    (bounds[4] + bounds[5]) / 2)
    plane.SetNormal(0, 0, 1)
 
    # 计算vtp文件各个点到平面的有向距离
    scalars = vtkDoubleArray()
    numberOfPoints1 = reader.GetOutput().GetNumberOfPoints()
    scalars.SetNumberOfTuples(numberOfPoints1)
    pts = reader.GetOutput().GetPoints()
    for i in range(0, numberOfPoints1):
        point = pts.GetPoint(i)
        """
        EvaluateFunction 接收一个三维点作为输入,并返回一个带符号的标量值，值的大小就是输入点到平面的距离
        如果点在平面的正法线方向一侧，返回值是正数
        如果点在平面的负法线方向一侧，返回值是负数
        """
        scalars.SetTuple1(i, plane.EvaluateFunction(point))
    """
    告诉 VTK ------ 模型的每个点现在有一个标量值，这个标量值就是点到平面的距离。
    后面 vtkContourFilter 就会根据这些标量值来提取等值面
    """
    reader.GetOutput().GetPointData().SetScalars(scalars)
    reader.GetOutput().GetPointData().GetScalars().GetRange()
 
    """
    vtkContourFilter   VTK 中用于从标量场（scalar field）中提取等值面（或等值线）的核心算法
    """
    cutter = vtkContourFilter()
    cutter.SetInputConnection(reader.GetOutputPort())
    cutter.ComputeScalarsOff()
    cutter.ComputeNormalsOff()
    """
    GenerateValues  指定如何生成等值线
    第1个参数，指定要生成的等值线的数量
    第2个参数，指定等值线的最小值
    第3个参数，指定等值线爱你的最大值
    """
    cutter.GenerateValues(num_of_cuts, 0.99 * reader.GetOutput().GetPointData().GetScalars().GetRange()[0],
                          0.99 * reader.GetOutput().GetPointData().GetScalars().GetRange()[1])
 
    cutterMapper = vtkPolyDataMapper()
    cutterMapper.SetInputConnection(cutter.GetOutputPort())
    cutterMapper.ScalarVisibilityOff()
 
    cutterActor = vtkActor()
    cutterActor.SetMapper(cutterMapper)
    cutterActor.GetProperty().SetColor(colors.GetColor3d("Banana"))
    cutterActor.GetProperty().SetLineWidth(2)
 
    modelMapper = vtkPolyDataMapper()
    modelMapper.SetInputConnection(reader.GetOutputPort())
    modelMapper.ScalarVisibilityOff()
 
    modelActor = vtkActor()
    modelActor.GetProperty().SetColor(colors.GetColor3d("Flesh"))
    modelActor.SetMapper(modelMapper)
 
    renderer = vtkRenderer()
    renderer.AddActor(cutterActor)
    # renderer.AddActor(modelActor)
 
    renderWindow = vtkRenderWindow()
    renderWindow.AddRenderer(renderer)
    renderWindow.SetSize(600, 600)
    renderWindow.SetWindowName('CutWithCutScalars')
 
    interactor = vtkRenderWindowInteractor()
    interactor.SetRenderWindow(renderWindow)
 
    renderer.SetBackground(colors.GetColor3d('Burlywood'))
    renderer.GetActiveCamera().SetPosition(0, -1, 0)
    renderer.GetActiveCamera().SetFocalPoint(0, 0, 0)
    renderer.GetActiveCamera().SetViewUp(0, 0, 1)
    renderer.GetActiveCamera().Azimuth(30)
    renderer.GetActiveCamera().Elevation(30)
 
    renderer.ResetCamera()
    renderWindow.Render()
 
    interactor.Start()
 
 
if __name__ == '__main__':
    main()