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

[Justin Rosen]

Grabbing a copy of the camera in a separate thread seems to do the trick.
 Can anyone shed some light onto this topic?

vtkCamera *camera = vtkCamera::New();
camera->ShallowCopy(renderer->GetActiveCamera());

Thanks,
Justin

On Sat, Apr 28, 2012 at 9:52 PM, Justin Rosen <jmylesrosen at gmail.com> wrote:

> 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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