[vtkusers] Refreshing the vtkRenderWindow

[David Gobbi]

Hi Vivek,

Instead of using VTK observers, you might want to use a timer generated by
whatever GUI toolkit you are using.  E.g. in Tk you would use 'after.'

Please not that these "Timers" don't have anything to do with threads,
they are generated by the GUI event loop, which ensures that they are
synchronous with your main thread execution.  If you could call a "Render"
from another thread (which you can't), then you wouldn't have to deal
with timers in the first place.

Good luck!

 - David

On Fri, 30 Apr 2004, Vivek Gupta wrote:

> Hi David,
>
> Better....  What happened was interesting.  I left all of my code the same, I have the CreateTimer(VTKI_TIMER_FIRST) right before my AddObserver, before my interactor->Start().  I added the one line you suggested in my observor.
>
> When the code starts it does exactly what you said, it starts printing out my line from the Observor over and over. This is great, since this means it is firing of the event continuously like I want, without my having touched the Window.  However, the minute I interact with the window with my mouse (to rotate the view) the events stop firing in an automated fashing and return to firing only when I am interacting with the window through manipulation with the interactor.
>
> Is their any way I can use some other timer thread to send the VTKRenderer or VTKRenderWindowInteractor a refresh or windows REPAINT event?
>
> Thanks a lot for your help,
> Vivek
>
> On Friday, April 30, 2004, at 11:07AM, David Gobbi <dgobbi at imaging.robarts.ca> wrote:
>
> >Hi Vivek,
> >
> >I think I see the problem, the VTK timer is a one-shot timer that
> >is started, via interactor->CreateTimer(), every time an event occurs.
> >
> >Try adding
> >  interactor->CreateTimer(VTKI_TIMER_UPDATE);
> >after your print statement in your observer method, so that the
> >timer is re-started every time.
> >
> > - David
> >
> >On Fri, 30 Apr 2004, Vivek Gupta wrote:
> >
> >> David,
> >>
> >> I did try out a simplified version of this with printing to see what
> >> would happen.  The results aren't quite what I expected. Here is what I
> >> did:
> >>
> >> 1)  I created a callback, currently all this does is print the fact
> >> that it was called to the console
> >> 2) From the RenderWindowInteractor I created a timer
> >> 3) I added an observer to listen to vtkCommand::TimerEvent
> >>
> >> What I found was that I get my print out only when interacting with the
> >> interactor window.  Unfortunately when I am using my external device I
> >> am not directly interacting with the the renderwindow, so this isn't
> >> the behavior I wanted.  I'm hoping I can move my cursor around and have
> >> it update as you described in your idea.
> >>
> >> Do I need to write my own event loop? But then I will have problems
> >> handling the RenderWindowInteractor, right?
> >>
> >> Thanks,
> >> Vivek
> >>
> >> On Apr 26, 2004, at 13:38, David Gobbi wrote:
> >>
> >> > Hi Vivek,
> >> >
> >> > You can only call "Render" from the main thread (i.e. from the thread
> >> > that created the vtkRenderWindow).
> >> >
> >> > The proper solution to your problem is to get the device thread to
> >> > communicate the coordinate information to the main thread via a mutex
> >> > lock (specifically, a vtkMutexLock).
> >> >
> >> > For example, you could have a mutex lock called "renderLock" and four
> >> > variables x, y, z and "render":
> >> >
> >> > vtkMutexLock *renderLock = vtkMutexLock::New();
> >> > double x, y, z;
> >> > int render;
> >> >
> >> > So every time your device wanted to render the window, it would do
> >> > this:
> >> >
> >> >   renderLock->Lock();
> >> >   <set x, y, and z variables>
> >> >   render = 1;
> >> >   renderLock->Unlock();
> >> >
> >> > Then the main thread would have to check every-so-often to see if the
> >> > "render" variable is set, you could add an observer for an interactor
> >> > "Timer" event to do this:
> >> >
> >> >   if (render == 1)
> >> >     {
> >> >     renderLock->Lock();
> >> >     <use x, y and z to set up the scene>
> >> >     render = 0;
> >> >     renderLock->Unlock();
> >> >     window->Render();
> >> >     }
> >> >
> >> > I have used tricks similar to this for the Flock of Birds, the Logitech
> >> > 3D Mouse, and the Northern Digital POLARIS in order to separate the
> >> > device thread from the main VTK thread.
> >> >
> >> >  - David
> >> >
> >> >
> >> > On Mon, 26 Apr 2004, Vivek Gupta wrote:
> >> >
> >> >> Hello All,
> >> >>
> >> >> I have a case where I have a separate thread that is running and
> >> >> interfaces with a device.  I use the devices coordinates to update the
> >> >> location of an actor (3D cursor on the screen).  I also have
> >> >> vtkRenderWindowInteractor associated with vtkRenderWindow so that in
> >> >> the
> >> >> window I can use the built-in abilities to manipulate the camera.
> >> >> What
> >> >> I'd like to be able to do is as I manipulate my device is refresh the
> >> >> vtkRenderWindow to display the actor at the updated coordinates.
> >> >>
> >> >> I've tried a variety of methods to do this (vtkRenderWindow->Render(),
> >> >> this gives some form of openGL error, which I haven't been able to
> >> >> read)
> >> >> and none of them seems to work.  Is there a specific way I have to go
> >> >> about getting the reference to vtkRenderWindow or some other way to
> >> >> notify it that the actor has been modified so refresh the drawing.
> >> >> Do I
> >> >> have use LevelOfDetail in order to set an auto-refresh rate?
> >> >>
> >> >> Thanks,
> >> >> Vivek
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