Save screen capture in pyvista including interaction / rotation

I’m looking for a way to effectively capture the frame buffer during interaction in pyvista so that I can produce a video afterwards of the model moving around on the screen.

The problem I’ve encountered is that when I click the screen to interact with the viewer/plotter, no frames are written while the mouse button is pressed and the model is moving to its next position. This results in ‘jerky’ movements in the video.

Is there a way around this behavior to effectively do something like a screen capture of the plotter window, even when being manipulated? Maybe through direct access to the frame buffer or something similar?

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import pyvista as pv
import numpy as np
from pyvista import examples

import matplotlib as mpl
import matplotlib.pyplot as plt

px = int(round(1920*0.4))
py = int(round(1000*0.4))

mesh = examples.download_st_helens().warp_by_scalar()

p = pv.Plotter()
p.set_background(color='k')
cmap = mpl.cm.get_cmap('viridis')
p.add_mesh(mesh, lighting=True, texture=False, cmap=cmap, smooth_shading=True)
p.show_grid()
p.show(window_size=[px,py], auto_close=False, interactive_update=True)
p.render()
p.open_movie('anim.mp4',framerate=60)

i=0
while (i<100):
    i+=1
    p.write_frame()
    print(i)

p.close()

Answer

I have added an example in pure VTK, where a cube is rotated and a smooth video is captured with the rotation. Afterwards, the interactor is started and the user can interact with the scene afterwards.

import os
import vtk
import numpy as np

def vtkRotationMovie(renderWindow, filename='c:/test.avi'):
  global degrees
  degrees = 0

  windowToImageFilter = vtk.vtkWindowToImageFilter()
  windowToImageFilter.SetInput(renderWindow)
  windowToImageFilter.SetInputBufferTypeToRGB()
  windowToImageFilter.ReadFrontBufferOff()
  windowToImageFilter.Update()

  if os.name == 'nt':
    writer = vtk.vtkAVIWriter()
  else:
    writer = vtk.vtkOggTheoraWriter()
  writer.SetInputConnection(windowToImageFilter.GetOutputPort())
  writer.SetRate(10) # Not needed for Ogg

  try:
    os.remove(filename)
  except OSError:
    pass
  writer.SetFileName(filename)
  writer.Start()

  timerId = renderWindow.GetInteractor().CreateRepeatingTimer(50)
  def cb(interactor, event):
    global degrees
    step = 5
    if (degrees > 359):
      interactor.DestroyTimer(timerId)
      writer.End()
      return
    interactor.GetRenderWindow().Render()
    cam = interactor.GetRenderWindow().GetRenderers().GetFirstRenderer().GetActiveCamera()
    cam.Azimuth(step)
    cam.OrthogonalizeViewUp()
    windowToImageFilter.Modified()
    writer.Write()
    degrees = degrees + step
  renderWindow.GetInteractor().AddObserver('TimerEvent', cb)
  renderWindow.GetInteractor().Start()

# create a rendering window and renderer
ren = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)

# create a renderwindowinteractor
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

# create cube
cube = vtk.vtkCubeSource()

# mapper
cubeMapper = vtk.vtkPolyDataMapper()
cubeMapper.SetInputConnection(cube.GetOutputPort())

# actor
cubeActor = vtk.vtkActor()
cubeActor.SetMapper(cubeMapper)

# assign actor to the renderer
ren.AddActor(cubeActor)
ren.SetBackground(.3,.2,.1)
# enable user interface interactor
iren.Initialize()
renWin.Render()

vtkRotationMovie(renWin, filename='./test.avi')

iren.Start()