VTKExamples/Python/GeometricObjects/OrientedArrow
Description¶
This example illustrates how to create and display an arrow that passes through two points.
It demonstrates two different ways to apply the transform:
Use vtkTransformPolyDataFilter to create a new transformed polydata. This method is useful if the transformed polydata is needed later in the pipeline, e.g. vtkGlyph3DFilter.¶
Apply the transform directly to the actor using vtkProp3D's SetUserMatrix. No new data is produced.¶
Switch between the two methods by setting USER_MATRIX to either or as documented in the script.
Code¶
OrientedArrow.py
#!/usr/bin/env python import vtk import random ''' There are two alternative ways to apply the transform. 1) Use vtkTransformPolyDataFilter to create a new transformed polydata. This method is useful if the transformed polydata is needed later in the pipeline To do this, set USER_MATRIX = True 2) Apply the transform directly to the actor using vtkProp3D's SetUserMatrix. No new data is produced. To do this, set USER_MATRIX = False ''' USER_MATRIX = False #Create an arrow. arrowSource = vtk.vtkArrowSource() # Generate a random start and end point random.seed(8775070) startPoint = [0 for i in range(3)] startPoint[0] = random.uniform(-10,10) startPoint[1] = random.uniform(-10,10) startPoint[2] = random.uniform(-10,10) endPoint = [0 for i in range(3)] endPoint[0] = random.uniform(-10,10) endPoint[1] = random.uniform(-10,10) endPoint[2] = random.uniform(-10,10) # Compute a basis normalizedX = [0 for i in range(3)] normalizedY = [0 for i in range(3)] normalizedZ = [0 for i in range(3)] # The X axis is a vector from start to end math = vtk.vtkMath() math.Subtract(endPoint, startPoint, normalizedX) length = math.Norm(normalizedX) math.Normalize(normalizedX) # The Z axis is an arbitrary vector cross X arbitrary = [0 for i in range(3)] arbitrary[0] = random.uniform(-10,10) arbitrary[1] = random.uniform(-10,10) arbitrary[2] = random.uniform(-10,10) math.Cross(normalizedX, arbitrary, normalizedZ) math.Normalize(normalizedZ) # The Y axis is Z cross X math.Cross(normalizedZ, normalizedX, normalizedY) matrix = vtk.vtkMatrix4x4() # Create the direction cosine matrix matrix.Identity() for i in range(3): matrix.SetElement(i, 0, normalizedX[i]) matrix.SetElement(i, 1, normalizedY[i]) matrix.SetElement(i, 2, normalizedZ[i]) # Apply the transforms transform = vtk.vtkTransform() transform.Translate(startPoint) transform.Concatenate(matrix) transform.Scale(length, length, length) # Transform the polydata transformPD = vtk.vtkTransformPolyDataFilter() transformPD.SetTransform(transform) transformPD.SetInputConnection(arrowSource.GetOutputPort()) #Create a mapper and actor for the arrow mapper = vtk.vtkPolyDataMapper() actor = vtk.vtkActor() if USER_MATRIX: mapper.SetInputConnection(arrowSource.GetOutputPort()) actor.SetUserMatrix(transform.GetMatrix()) else: mapper.SetInputConnection(transformPD.GetOutputPort()) actor.SetMapper(mapper) # Create spheres for start and end point sphereStartSource = vtk.vtkSphereSource() sphereStartSource.SetCenter(startPoint) sphereStartMapper = vtk.vtkPolyDataMapper() sphereStartMapper.SetInputConnection(sphereStartSource.GetOutputPort()) sphereStart = vtk.vtkActor() sphereStart.SetMapper(sphereStartMapper) sphereStart.GetProperty().SetColor(1.0, 1.0, .3) sphereEndSource = vtk.vtkSphereSource() sphereEndSource.SetCenter(endPoint) sphereEndMapper = vtk.vtkPolyDataMapper() sphereEndMapper.SetInputConnection(sphereEndSource.GetOutputPort()) sphereEnd = vtk.vtkActor() sphereEnd.SetMapper(sphereEndMapper) sphereEnd.GetProperty().SetColor(1.0, .3, .3) #Create a renderer, render window, and interactor renderer = vtk.vtkRenderer() renderWindow = vtk.vtkRenderWindow() renderWindow.AddRenderer(renderer) renderWindowInteractor = vtk.vtkRenderWindowInteractor() renderWindowInteractor.SetRenderWindow(renderWindow) #Add the actor to the scene renderer.AddActor(actor) renderer.AddActor(sphereStart) renderer.AddActor(sphereEnd) renderer.SetBackground(.1, .2, .3) # Background color dark blue #Render and interact renderWindow.Render() renderWindowInteractor.Start()