渲染在 vtkCommand 中创建的演员（回调）答案

【问题标题】：Rendering an actor created within a vtkCommand (callback)渲染在 vtkCommand 中创建的演员（回调）
【发布时间】：2019-01-23 23:45:26
【问题描述】：

我正在尝试编写一个程序，该程序在按下箭头键时显示和循环显示不同文件格式的图像。我发现设置我的 reader->mapper->actor 管道，然后启动我的 RenderWindowInteractor 允许渲染actor，但是将此代码移动到 RenderWindowInteractor 的 KeyPressEvent 的回调不允许渲染actor。事件循环开始后是否需要额外的步骤来设置新的参与者，还是我犯了其他错误？

import vtk

#Create the renderer that will display our actors
ren = vtk.vtkRenderer()

actor = None

#Maps the data from the Nifti file 'filename' onto a vtkImageSlice actor
def LoadNifti():
    # load head MRI in NIFTI format
    reader = vtk.vtkNIFTIImageReader()
    reader.SetFileName("head.nii")
    reader.Update()

    # Add an ImageSliceMapper, which maps data to an ImageSlice Actor
    mapper = vtk.vtkImageSliceMapper()
    #Set the slice position to the camera focal point
    mapper.SliceAtFocalPointOn()
    mapper.SetInputConnection(reader.GetOutputPort())

    # Add an ImageSlice actor, which represents a slice as an image
    global actor
    actor = vtk.vtkImageSlice()
    actor.SetMapper(mapper)

#Placeholder for when I have DICOM working
def ShowDICOM(filename):
    pass


#Create a RenderWindow to display images from the Renderer
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)

#Wrap the RenderWindow in a RenderWindowInteractor to catch key and mouse events
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

def foo():
    LoadNifti()
    ren.AddActor(actor)

##Extend the default functionality of the interactor and its style with custom listeners
def KeyPressEvent(obj, ev):
    foo()
    print("This verifies that the callback is triggered")
iren.AddObserver("KeyPressEvent", KeyPressEvent)        

#Start the program
###########################################################################
# WHEN foo() IS PRESENT BELOW, THE ACTOR WILL RENDER IMMEDIATELY.
# WHEN foo() IS ABSENT BELOW, CALLING foo() BY TRIGGERING THE KeyPressEvent
# IS NOT SUFFICIENT TO HAVE THE ACTOR RENDER.
###########################################################################
foo()
#According to the docs, the Start method will initialize iren and render renWin automatically
iren.Start()

【问题讨论】：

标签： python vtk

【解决方案1】：

好吧，您绝对可以在回调中添加或删除演员。要立即再次渲染场景，只需调用iren.Render()。

当您启动一个没有任何可见演员且没有明确定义的相机的渲染器时，通常需要ResetCamera。自动ResetCamera在初始化期间只调用一次，这就是为什么在iren.Start()之前调用foo()会使对象可见的原因。

def foo():
    LoadNifti()
    ren.AddActor(actor)
    ren.ResetCamera() # should that be necessary
    iren.Render()

【讨论】：

vtkRenderer.ResetCamera() 是我需要使用的 100% 方法。非常感谢您的帮助 - 如果有机会，我会付出代价。