如何使用python將3D vtk渲染的場景導出到paraview？

Question

我已經編寫了一個代碼在python中使用vtk生成圓柱對象。 此代碼在產生3D場景的地方效果很好，在這里我可以縮放或旋轉已制成的圓柱體。 問題是我想將此渲染的場景導出到paraview，以查看並保存以供以后使用。 我怎樣才能做到這一點？ 以下是產生帶有圓柱體的Y形的代碼：

import vtk
import numpy as np

'''
Adding multiple Actors to one renderer scene using VTK package with python api.
Each cylinder is an Actor with three input specifications: Startpoint, Endpoint and radius.
After creating all the Actors, the preferred Actors will be added to a list and that list will be our input to the 
renderer scene.
A list or numpy array with appropriate 3*1 shape could be used to specify starting and ending points.

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 = True


def cylinder_object(startPoint, endPoint, radius, my_color="DarkRed"):
    colors = vtk.vtkNamedColors()

    # Create a cylinder.
    # Cylinder height vector is (0,1,0).
    # Cylinder center is in the middle of the cylinder
    cylinderSource = vtk.vtkCylinderSource()
    cylinderSource.SetRadius(radius)
    cylinderSource.SetResolution(50)

    # Generate a random start and end point
    # startPoint = [0] * 3
    # endPoint = [0] * 3

    rng = vtk.vtkMinimalStandardRandomSequence()
    rng.SetSeed(8775070)  # For testing.8775070

    # Compute a basis
    normalizedX = [0] * 3
    normalizedY = [0] * 3
    normalizedZ = [0] * 3

    # The X axis is a vector from start to end
    vtk.vtkMath.Subtract(endPoint, startPoint, normalizedX)
    length = vtk.vtkMath.Norm(normalizedX)
    vtk.vtkMath.Normalize(normalizedX)

    # The Z axis is an arbitrary vector cross X
    arbitrary = [0] * 3
    for i in range(0, 3):
        rng.Next()
        arbitrary[i] = rng.GetRangeValue(-10, 10)
    vtk.vtkMath.Cross(normalizedX, arbitrary, normalizedZ)
    vtk.vtkMath.Normalize(normalizedZ)

    # The Y axis is Z cross X
    vtk.vtkMath.Cross(normalizedZ, normalizedX, normalizedY)
    matrix = vtk.vtkMatrix4x4()
    # Create the direction cosine matrix
    matrix.Identity()
    for i in range(0, 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)  # translate to starting point
    transform.Concatenate(matrix)  # apply direction cosines
    transform.RotateZ(-90.0)  # align cylinder to x axis
    transform.Scale(1.0, length, 1.0)  # scale along the height vector
    transform.Translate(0, .5, 0)  # translate to start of cylinder

    # Transform the polydata
    transformPD = vtk.vtkTransformPolyDataFilter()
    transformPD.SetTransform(transform)
    transformPD.SetInputConnection(cylinderSource.GetOutputPort())

    # Create a mapper and actor for the arrow
    mapper = vtk.vtkPolyDataMapper()
    actor = vtk.vtkActor()
    if USER_MATRIX:
        mapper.SetInputConnection(cylinderSource.GetOutputPort())
        actor.SetUserMatrix(transform.GetMatrix())
    else:
        mapper.SetInputConnection(transformPD.GetOutputPort())
    actor.SetMapper(mapper)
    actor.GetProperty().SetColor(colors.GetColor3d(my_color))
    return actor


def render_scene(my_actor_list):
    renderer = vtk.vtkRenderer()
    for arg in my_actor_list:
        renderer.AddActor(arg)
    namedColors = vtk.vtkNamedColors()
    renderer.SetBackground(namedColors.GetColor3d("SlateGray"))

    window = vtk.vtkRenderWindow()
    window.SetWindowName("Oriented Cylinder")
    window.AddRenderer(renderer)

    interactor = vtk.vtkRenderWindowInteractor()
    interactor.SetRenderWindow(window)

    # Visualize
    window.Render()
    interactor.Start()


if __name__ == '__main__':

    my_list = []
    p0 = np.array([0, 0, 0])
    p1 = np.array([0, 10, 0])
    p2 = np.array([7, 17, 0])
    p3 = np.array([-5, 15, 0])
    my_list.append(cylinder_object(p0, p1, 1, "Red"))
    my_list.append(cylinder_object(p1, p2, 0.8, "Green"))
    my_list.append(cylinder_object(p1, p3, 0.75, "Navy"))
    render_scene(my_list)

我有多個演員，所有演員都在一個渲染場景中一起渲染，我可以將每個演員傳遞到vtk.vtkSTLWriter嗎？ 這似乎不起作用！

Answer 1

您正在尋找的是vtkExporter類的子類 ，根據鏈接的doco：

vtkExporter是將場景導出到文件的抽象類。 它與vtkWriter非常相似，不同之處在於寫入器只寫出對象的幾何和拓撲數據，而輸出者可以在其中寫出材料特性，照明，相機參數等。

從類的繼承圖中可以看到，大約有15個類支持將此類場景導出到文件中，並可以在適當的閱讀器中查看。

恕我直言，最讓您幸運的是vtkVRMLExporter類，因為它是一種相當常見的格式。 話雖這么說，但我不相信Paraview支持VRML文件（至少基於我發現的一些非常古老的帖子），但是我確定MayaVi可以。

或者，您可以如上所述將對象導出到STL文件中，但是STL文件僅包含三角形坐標和有關其連接方式的信息。 這樣的文件可能無法描述場景信息，例如相機或照明信息。 最后我檢查了一個STL文件只能包含一個對象，因此您的三個柱面最終將成為一個合並對象，因此可能不是您想要的。

Answer 2

我添加了這些代碼，它從渲染的場景創建了一個VRML文件。

exporter = vtk.vtkVRMLExporter()
exporter.SetRenderWindow(window)
exporter.SetFileName("cylinders.wrl")
exporter.Write()
exporter.Update()