Add the ability to set custom render window and renderer for pcl_visualizer

[denix56]

Hi all.
I started working on it due to that pcl visualizer does not work correctly with new QVTKOpenGLWidget. It requires vtkGenericOpenGLRenderWindow.
I propose to add the constructor, that takes the smart pointers to render window and renderer and assigns them to internal pointers
PCLVisualizer(int &argc, char **argv, const std::string &name, vtkSmartPointer<vtkRenderWindow>& win, vtkSmartPointer<vtkRenderer>& renderer, PCLVisualizerInteractorStyle* style = PCLVisualizerInteractorStyle::New(), const bool create_interactor = true);

But there is small problem - in such signature we miss the default parameter for name. But i think the it will be not a problem for users to set it.

[taketwo]

Hi, before we can jump into the discussion, I would like to have a better understanding of the problem we are addressing:

• by "new" QVTKOpenGLWidget which one do you mean (VTK/Qt version)?
• what exactly means "does not work"?
• short example project that demonstrates the problem (you can upload it as a Gist)
• any relevant information including tutorial links that are obsolete (provide code that does not work with new widget)

[denix56]

http://pointclouds.org/documentation/tutorials/qt_visualizer.php
If we follow this tutorial and write our code base on it we get

 // Set up the QVTK window
  viewer.reset (new pcl::visualization::PCLVisualizer ("viewer", false));
  ui->qvtkWidget->SetRenderWindow (viewer->getRenderWindow ());
  viewer->setupInteractor (ui->qvtkWidget->GetInteractor (), ui->qvtkWidget->GetRenderWindow ());
  ui->qvtkWidget->update ();

And crashes with debug message saying that the vtkGenericOpenGLRenderWindow is required, but vtkWin32OpenGLRenderWindow was received.

I meant by 'new' that QVTKOpenGLWidget was added after qVTKWidget and requires Qt 5.4

[taketwo]

What are the reasons to not use the "classical" QVTKWidget?

[denix56]

QVTKOpenGLWidget is intended to be a replacement for QVTKWidget when using Qt 5, also it has features, that might be used in my project.

Also, I have found better solution - make win_ and some other fields protected instead of private and implement new class based on PclVisualizer.

[denix56]

Also, it will give us the ability to use the visualizer in VR with vtkExternalOpenGLRenderWindow

[taketwo]

Quick googling about QVTKOpenGLWidget vs. QVTKWidget does not yield many results. Basically, the only information I found is this passage from the release notes of VTK 8:

The new QVTKOpenGLWidget leverages Qt’s new OpenGL context creation mechanism and is meant to be a replacement for QVTKWidget for Qt5. Note that as of release time there are unresolved transparency related bugs that show up with this new Qt5 enabling class on some platforms.

Additionally, I see this list of changes, with multiple bugfixes for QVTKOpenGLWidget, from which I conclude that it is quite unstable.

With this in mind, keeping PCLVisualizer compatible with QVTKWidget is the priority. If there is an easy and non-intrusive way to let users couple it with the new QVTKOpenGLWidget, then let's do this.

[denix56]

Ok, I will start working on it.