vtk绘制带箭头的可设置角度长度的直线

以下是一个用VTK绘制带箭头的可设置角度长度的直线的示例代码：

import vtk

# 创建箭头
arrowSource = vtk.vtkArrowSource()
arrowSource.SetShaftRadius(0.02)
arrowSource.SetTipLength(0.2)

# 创建线
lineSource = vtk.vtkLineSource()
lineSource.SetPoint1(0,0,0)
lineSource.SetPoint2(1,1,0)

# 创建箭头mapper和actor
arrowMapper = vtk.vtkPolyDataMapper()
arrowMapper.SetInputConnection(arrowSource.GetOutputPort())

arrowActor = vtk.vtkActor()
arrowActor.SetMapper(arrowMapper)

# 创建线mapper和actor
lineMapper = vtk.vtkPolyDataMapper()
lineMapper.SetInputConnection(lineSource.GetOutputPort())

lineActor = vtk.vtkActor()
lineActor.SetMapper(lineMapper)

# 计算箭头位置和方向
arrowPosition = lineSource.GetPoint2()
arrowDirection = [lineSource.GetPoint2()[0] - lineSource.GetPoint1()[0], lineSource.GetPoint2()[1] - lineSource.GetPoint1()[1], lineSource.GetPoint2()[2] - lineSource.GetPoint1()[2]]
arrowLength = vtk.vtkMath.Normalize(arrowDirection)
arrowActor.SetPosition(arrowPosition)
arrowActor.SetOrientation(vtk.vtkMath.RotationBetweenVectors([1,0,0], arrowDirection))

# 设置箭头长度
arrowActor.SetScale(arrowLength, arrowLength, arrowLength)

# 创建渲染器和窗口
renderer = vtk.vtkRenderer()
renderer.AddActor(lineActor)
renderer.AddActor(arrowActor)

renderWindow = vtk.vtkRenderWindow()
renderWindow.AddRenderer(renderer)

# 创建交互器
interactor = vtk.vtkRenderWindowInteractor()
interactor.SetRenderWindow(renderWindow)

# 开始渲染和交互
renderWindow.Render()
interactor.Start()

这个示例代码可以绘制一条从原点到(1,1,0)的直线，并在直线末端添加一个长度和方向可调的箭头。箭头方向和直线方向相同，箭头长度为直线长度的倍数。可以通过调整`lineSource.SetPoint1()`和`lineSource.SetPoint2()`来改变直线的起点和终点，通过调整`arrowSource.SetTipLength()`来改变箭头长度。