[vtkusers] Multi-threaded creation, display and deletion of actors

[Sebastien Jourdain]

Ok this is still wrong.

You can not have part of a vtk pipeline shared across 2 thread. Which is
the case for you as you call v->actor->GetMapper()->Update(); while the
actor is already bind to the renderer that is driven by the VTK thread.

You should create the mapper and the actor within your thread and transfer
the actor to the VTK thread with the locking mechanism.
But before giving that actor, as I said, you should call update on the
mapper.

Basically what you've done could work if you don't call
v->actor->GetMapper()->Update();

Seb


On Thu, Feb 21, 2013 at 4:21 PM, Dženan Zukić <dzenanz at gmail.com> wrote:

> Thank you for your help Sebastien. Other issues appeared as well after I
> have introduced multi-threading. The VTK-related part is finished. Here is
> a sketch of my solution:
>
> void timerFunction()
> {
>     if (render)
>     {
>         renderLock->Lock();
>         render=false;
>         renderLock->Unlock();
>         mainForm.vis->GetRenderWindow()->Render();
>   QApplication::processEvents();
>     }
> }
>
> void threadFunction()
> {
>     while (notFinished)
>     {
>         //calculate stuff
>         vtkSmartPointer<vtkPolyData> pd=v->getPoly();
>         renderLock->Lock();
>         render=true;
>         ((vtkPolyDataMapper *)v->actor->GetMapper())->SetInput(pd);
>         v->actor->GetMapper()->Modified();
>         renderLock->Unlock();
>         v->actor->GetMapper()->Update();
>     }
> }
>
>
> On Wed, Feb 20, 2013 at 8:06 PM, Sebastien Jourdain <
> sebastien.jourdain at kitware.com> wrote:
>
>> The add actor should be done by the same VTK thread that is rendering.
>> So only one thread can do that action.
>> Moreover, you should call Update() on the mapper within each of your
>> thread to reduce the work that will be done by the main vtk thread.
>>
>> Hope that make sense,
>>
>> Seb
>>
>> PS: VTK is not thread safe, but I've already done something similar to
>> what you did without any issue.
>>
>>
>> On Wed, Feb 20, 2013 at 5:18 PM, Dženan Zukić <dzenanz at gmail.com> wrote:
>>
>>> I have a need to modify the scene from multiple threads.
>>>
>>> Each thread looks like:
>>> {
>>> for (i=1 to 100)
>>> create mesh_i;
>>> convert it to vtkPolyData;
>>> if exists actor delete it;
>>> create actor with pd;
>>> add actor to renderer;
>>> update display;
>>> }
>>>
>>> How best to accomplish this? I already tried this<http://www.vtk.org/pipermail/vtkusers/2004-April/073478.html>approach, but it does not work. It always crashes before returning from
>>> Render() method. Crashes are at random location in VTK rendering code.
>>>
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