[vtkusers] threads and refreshing vtkRenderWindow

Mon May 18 18:16:55 EDT 2009

Many thanks!!!
This morning I've actually found the solution using QT....just emitting timer events builting up a QTimer with QT and connecting my main thread to capture those events. In that case I'll call the Render() function staying in the main one....

Many thanks
GC.

> Date: Mon, 18 May 2009 08:52:20 -0600
> From: clinton at elemtech.com
> To: ilferraresebono at hotmail.it
> CC: david.cole at kitware.com; vtkusers at vtk.org
> Subject: Re: [vtkusers] threads and refreshing vtkRenderWindow
> 
> 
> Have you look at this?
> http://doc.trolltech.com/qq/qq06-glimpsing.html
> It would need adjustments if using VTK instead, and I'm curious if it'll 
> work just fine.
> 
> But, first, you could try overloading QVTKWidget::paintEvent() to do 
> nothing.
> Then in your QThread::run, you create all your VTK objects and do your 
> Render() calls from there.
> You're getting the wglMakeCurrent error because the context is current 
> in the main thread, and you're trying to make it current in another 
> thread as well.  That is not allowed.  
> http://msdn.microsoft.com/en-us/library/dd374387(VS.85).aspx
> 
> Clint
> 
> Giancarlo Amati wrote:
> > Nope I don't,....I was just telling you how I did organize my 
> > code...and as you said the Render() function should be called only 
> > from the thread that the MAIN one, I was simply asking..if calling a 
> > function which belongs to the main thread (which is the Parent from 
> > the 2nd one) is the reason that generates the wglMakeCurrent error.
> > Moreover, as the documentation about the vtkMutexLock class on the vtk 
> > website is quite poor, I was just wondering if there were any other 
> > resource.
> >
> > My project is mainly about a device system which tracks IReds 
> > visulalized with VTK, basically what I am doing is a real-time 
> > animation with QT and VTK. So, as I need to update the VTK scene 
> > without interfering with the QT events, the QT users group told me 
> > that the best way is to create a thread which updates the scene. But 
> > apparently this generates a wglMakeCurrent error for the reasons you 
> > told me.
> >
> >
> > GC.
> >
> > ------------------------------------------------------------------------
> > Date: Fri, 15 May 2009 11:08:20 -0400
> > Subject: Re: [vtkusers] threads and refreshing vtkRenderWindow
> > From: david.cole at kitware.com
> > To: ilferraresebono at hotmail.it
> > CC: vtkusers at vtk.org
> >
> > Are you asking us to tell you how your program is organized with 
> > respect to threads? (That's somewhat beyond the scope of the VTK 
> > mailing list.)
> >
> > It sounds like your project might be better off single-threaded.
> >
> > It would be better if you call UpdateMy3DObject from the same thread 
> > that actually does the rendering.
> >
> >
> > On Fri, May 15, 2009 at 10:59 AM, Giancarlo Amati 
> > <ilferraresebono at hotmail.it <mailto:ilferraresebono at hotmail.it>> wrote:
> >
> >     Many thanks,
> >
> >     what I have is a mainWindow which has functions for rendering and
> >     then a thread that calls a kind of "UpdateMy3Dobjects" function
> >     which belongs to the mainWindow object. Now,
> >     this "UpdateMy3DObjects" function works fine whenever that thread
> >     is not running while, I got the wglMakeCurrent error as soon as
> >     the thread runs the UpdateMy3Dobjects" function.
> >     So,
> >     as the UpdateMy3Dobjects function calls the RenderWindow->Render()
> >     method (renderwindow buidt in a QVTKWidget object of my GUI)
> >     calling that UpdateMy3DObject from the thread does correspond to a
> >     call form a thread different from the main one?
> >     In that case if I create a global variable, boolean for example
> >     which is true when I execute the UpdateMy3DObject function and
> >     false otherwise...would it help to synchronize these threads?
> >
> >     I checked out on the VTK documentation and I found the
> >     vktMutexLock class....and i tried to understand the example in the
> >     documetation which is a bit difficult honestly, but,....can that
> >     class be useful for my project?
> >
> >     many kind regards.
> >     Giancarlo
> >
> >     ------------------------------------------------------------------------
> >     Date: Fri, 15 May 2009 10:19:51 -0400
> >     Subject: Re: [vtkusers] threads and refreshing vtkRenderWindow
> >     From: david.cole at kitware.com <mailto:david.cole at kitware.com>
> >     To: ilferraresebono at hotmail.it <mailto:ilferraresebono at hotmail.it>
> >     CC: vtkusers at vtk.org <mailto:vtkusers at vtk.org>
> >
> >
> >     I will not claim to be cleverer, but I think I can answer the
> >     question:
> >
> >     Your mistake is calling vtkObjects from multiple threads without
> >     synchonization objects. In general, vtkObjects are only safely
> >     accessible by one thread at a time. Multi-thread access means you
> >     will have to use some sort of mutexes or locks to guarantee that
> >     only one thread at a time will call vtkObject methods.
> >     Furthermore, you should only attempt to call Render from the main
> >     GUI thread of your application.
> >
> >
> >     Hope this helps,
> >     David
> >
> >
> >     On Fri, May 15, 2009 at 9:25 AM, Giancarlo Amati
> >     <ilferraresebono at hotmail.it <mailto:ilferraresebono at hotmail.it>>
> >     wrote:
> >
> >         Hello vtkUSERS!!! This is an ash question for only the
> >         cleverer!! :D
> >
> >         I have a thread which modifies some data already in the
> >         vtkRenderWindow., now, the problem I have is when I want to
> >         refresh the window.
> >         I though calling something like renderWindow->Render() or
> >         renderer->render(), but I get some error messages related to
> >         "Resource already in use" and "wglMakeCurrent()" function error.
> >
> >         Where is my mistake and any idea about how to overcome it?
> >
> >         Kind regards.
> >
> >         GC.
> >
> >         ------------------------------------------------------------------------
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