[vtkusers] [python] vtkWin32OpenGLRenderWindow error when calling from thread vtkJPEGWriter.writer method

[David Cole]

VTK objects are not safe for accessing from multiple threads simultaneously.
Do all of your VTK object access from the same thread (or, alternatively,
use your own locking mechanism to ensure that only one thread at a time may
be accessing VTK objects)

And if you have a render window (on Windows at least) the GUI thread must
access VTK objects to respond to windows WM_ messages. So, generally, you
need to restrict access to VTK objects to the same thread that your render
window is responding to messages on...



On 11/19/07, Gustavo Serra Scalet <gsscalet at gmail.com> wrote:
>
> Hello to all,
>
> I'm trying to do a recording system that catches what is happening on the
> interactor and writes to a file. It has to be a thread or else the
> interactor will be unreachable while writing the movie. I've got the same
> error when I simplified the problem to just get a jpeg screenshot of the
> interactor when using threads. When I just call the method (
> self.img.Write) I don't get this error msg and everything goes perfectly.
> Can someone tell me what's wrong with my code?
>
>     def __init__(self, parent):
>         from vtk import vtkConeSource, vtkPolyDataMapper, vtkActor,
> vtkRenderer
>         # creates a dumme Cone
>         self.c = vtkConeSource()
>         self.c.SetHeight(3)
>         self.c.SetRadius(1)
>         self.c.SetResolution(10)
>         # creates a mapper with the cone
>         self.m = vtkPolyDataMapper()
>         self.m.SetInput(self.c.GetOutput())
>         # sets the actor with the mapper
>         self.a = vtkActor()
>         self.a.SetMapper(map)
>         self.a.SetPosition((0,0,0)) # middle of the screen
>         # puts the actor inside the renderer
>         self.r = vtkRenderer()
>         self.r.SetBackground((0,0,0)) # black bg
>         self.r.AddActor(self.a)
>         self.r.GetActiveCamera().SetPosition((10,10,10)) # camera at some
> position
>
>         # set the interactor with this renderer, attached to a wx panel
>         from vtk.wx.wxVTKRenderWindowInteractor import
> wxVTKRenderWindowInteractor
>         self.i = wxVTKRenderWindowInteractor(self.panel , -1 , size =
> self.panel.GetSize())
>         self.i.GetRenderWindow().AddRenderer(self.r)
>         self.i = interactor(self.r,self.panel)
>
>         # imaging filter
>         from vtk import vtkWindowToImageFilter
>         self.w2i = vtkWindowToImageFilter()
>         self.w2i.SetInput(self.i.GetRenderWindow())
>
>         # the jpeg object
>         from vtk import vtkJPEGWriter
>         self.img = vtkJPEGWriter()
>         self.img.SetQuality(80) # 80% is good
>         self.img.SetInput(self.w2i.GetOutput())
>         self.img.SetFileName('01.jpg')
>
>     def OnGetPictureButton(self, event):
>         # threading the image writing
>         from thread import start_new_thread
>         start_new_thread(self.img.Write,()) # error
>         # this way I don't get the error msg
>         # self.img.Write()
>         event.Skip()
>
> when "OnGetPictureButton" is called, I get this error on a pop up screen
> from vtk:
>
> "ERROR: In ..\..\VTK-5.0]\Rendering\vtkWin32OpenGLRenderWindow.cxx, lin
> vtkWin32OpenGLRenderWindow(02FE1640): wglMakeCurrent failed in Mak"
>
> Is it some lock issue?
>
> thx
>
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