[vtkusers] vtkCamera->GetFrustumPlanes segfault from a boost thread

[Justin Rosen]

It looks like vtkCamera->GetFrustumPlanes isn't thread safe?  It makes
quite a few changes to some of the it's member variables.  I tried adding a
mutex lock between vtkCommand::Start/EndEvent, but I'm still seg faulting.

Thanks,
Justin

On Sat, Apr 28, 2012 at 3:23 PM, Justin Rosen <jmylesrosen at gmail.com> wrote:

> If anyone one knows a bit about using vtk and boost threads I'd really
> appreciate the help.  I'm fairly new to vtk and threads in general and I'm
> trying to figure out why calling vtkCamera->GetFrustumPlanes from a boost
> thread eventually segfaults.  It takes quite a few of iterations before the
> segfault occurs.
>
> The general idea is that I have main application UI and a worker thread in
> the background which'll be doing some processing (Eventually
> updating/modifying a list of actors).  At the moment I'm just trying to get
> the cameras view frustum...
>
> If I remove the call to camera->GetFrustumPlanes the application runs
> without seg faulting.  Any idea what I may be doing wrong?
>
> void workerFunc(vtkCamera *camera)
> {
>   double prevUp[3] = {0, 0, 0};
>   double prevFocal[3] = {0, 0, 0};
>   double prevPos[3] = {0, 0, 0};
>
>   while(true){
>     double *up = camera->GetViewUp();
>     double *focal = camera->GetFocalPoint();
>     double *pos = camera->GetPosition();
>
>     bool viewpointChanged = false;
>
>     // Check up vector
>     if(up[0] != prevUp[0] || up[1] != prevUp[1] || up[2] != prevUp[2])
>       viewpointChanged = true;
>
>     // Check focal point
>     if(focal[0] != prevFocal[0] || focal[1] != prevFocal[1] || focal[2] !=
> prevFocal[2])
>       viewpointChanged = true;
>
>     // Check position
>     if(pos[0] != prevPos[0] || pos[1] != prevPos[1] || pos[2] !=
> prevPos[2])
>       viewpointChanged = true;
>
>     // If the viewpoints changed get the cameras frustum
>     if (viewpointChanged){
>       prevUp[0] = up[0]; prevUp[1] = up[1]; prevUp[2] = up[2];
>       prevFocal[0] = focal[0]; prevFocal[1] = focal[1]; prevFocal[2] =
> focal[2];
>       prevPos[0] = pos[0]; prevPos[1] = pos[1]; prevPos[2] = pos[2];
>
>       cout << "View Changed" << endl;
>       cout << "Up: <" << up[0] << ", " << up[1] << ", " << up[2] << ">" <<
> endl;
>       cout << "Focal: <" << focal[0] << ", " << focal[1] << ", " <<
> focal[2] << ">" << endl;
>       cout << "Pos: <" << pos[0] << ", " << pos[1] << ", " << pos[2] <<
> ">" << endl;
>
>       double planes[24];
>       camera->GetFrustumPlanes(1, planes);
>
>       for (int i=0; i < 6; i++){
>         cout << planes[(i*4)] << "x + " << planes[(i*4)+1] << "y + " <<
> planes[(i*4)+2] << "z + " << planes[(i*4)+3] << endl;
>       }
>     }
>   }
> }
>
> int
> main (int argc, char* argv[])
> {
>   vtkSmartPointer<vtkRenderer> renderer =
> vtkSmartPointer<vtkRenderer>::New ();
>   vtkRenderWindowInteractor *interactor = vtkRenderWindowInteractor::New
> ();
>   vtkSmartPointer<vtkRenderWindow> window =
> vtkSmartPointer<vtkRenderWindow>::New ();
>
>   window->AddRenderer (renderer);
>   window->SetSize (500, 500);
>   interactor->SetRenderWindow (window);
>
>   interactor->Initialize();
>
>   boost::thread workerThread(workerFunc, renderer->GetActiveCamera());
>
>   window->Render ();
>
>   vtkSmartPointer<vtkInteractorStyleTrackballCamera> style =
> vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New ();
>   interactor->SetInteractorStyle (style);
>
>   interactor->Start ();
>
>   return 0;
> }
>
>
> Thanks!
> Justin
>
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