VTK
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QVTKOpenGLWidget Class Reference

QOpenGLWidget subclass to house a vtkGenericOpenGLRenderWindow in a Qt application. More...

#include <QVTKOpenGLWidget.h>

Inherits QOpenGLWidget.

Collaboration diagram for QVTKOpenGLWidget:
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Signals

void mouseEvent (QMouseEvent *event)
 This signal will be emitted whenever a mouse event occurs within the QVTK window. More...
 

Public Member Functions

 QVTKOpenGLWidget (QWidget *parent=Q_NULLPTR, Qt::WindowFlags f=Qt::WindowFlags())
 
virtual ~QVTKOpenGLWidget ()
 
virtual QVTKInteractorGetInteractor ()
 Get the QVTKInteractor that was either created by default or set by the user. More...
 
virtual void setEnableHiDPI (bool enable)
 Enable or disable support for HiDPI displays. More...
 
void SetRenderWindow (vtkGenericOpenGLRenderWindow *win)
 Get/Set the currently used vtkGenericOpenGLRenderWindow. More...
 
void SetRenderWindow (vtkRenderWindow *win)
 Get/Set the currently used vtkGenericOpenGLRenderWindow. More...
 
virtual vtkRenderWindowGetRenderWindow ()
 Get/Set the currently used vtkGenericOpenGLRenderWindow. More...
 

Static Public Member Functions

static void copyFromFormat (const QSurfaceFormat &format, vtkRenderWindow *win)
 Sets up vtkRenderWindow ivars using QSurfaceFormat. More...
 
static void copyToFormat (vtkRenderWindow *win, QSurfaceFormat &format)
 Using the vtkRenderWindow, setup QSurfaceFormat. More...
 
static QSurfaceFormat defaultFormat ()
 Returns a typical QSurfaceFormat suitable for most applications using QVTKOpenGLWidget. More...
 

Protected Slots

virtual void cleanupContext ()
 Called as a response to QOpenGLContext::aboutToBeDestroyed. More...
 

Protected Member Functions

bool event (QEvent *evt) Q_DECL_OVERRIDE
 
void initializeGL () Q_DECL_OVERRIDE
 
void resizeGL (int w, int h) Q_DECL_OVERRIDE
 
void paintGL () Q_DECL_OVERRIDE
 
void moveEvent (QMoveEvent *event) Q_DECL_OVERRIDE
 
void mousePressEvent (QMouseEvent *event) Q_DECL_OVERRIDE
 
void mouseMoveEvent (QMouseEvent *event) Q_DECL_OVERRIDE
 
void mouseReleaseEvent (QMouseEvent *event) Q_DECL_OVERRIDE
 
void mouseDoubleClickEvent (QMouseEvent *event) Q_DECL_OVERRIDE
 
void requireRenderWindowInitialization ()
 This method is called to indicate that vtkRenderWindow needs to reinitialize itself before the next render (done in QVTKOpenGLWidget::paintGL). More...
 
virtual bool renderVTK ()
 This method may be called in paintGL to request VTK to do a render i.e. More...
 

Protected Attributes

vtkSmartPointer
< vtkGenericOpenGLRenderWindow
RenderWindow
 
QVTKInteractorAdapterInteractorAdaptor
 
bool EnableHiDPI
 
int OriginalDPI
 

Friends

class QVTKOpenGLWidgetObserver
 

Detailed Description

QOpenGLWidget subclass to house a vtkGenericOpenGLRenderWindow in a Qt application.

QVTKOpenGLWidget extends QOpenGLWidget to make it work with a vtkGenericOpenGLRenderWindow. This is akin to QVTKWidget except it uses Qt to create and manage the OpenGL context using QOpenGLWidget (added in Qt 5.4).

While QVTKOpenGLWidget is intended to be a replacement for QVTKWidget when using Qt 5, there are a few difference between QVTKOpenGLWidget and QVTKWidget.

Unlike QVTKWidget, QVTKOpenGLWidget only works with vtkGenericOpenGLRenderWindow. This is necessary since QOpenGLWidget wants to take over the window management as well as the OpenGL context creation. Getting that to work reliably with vtkXRenderWindow or vtkWin32RenderWindow (and other platform specific vtkRenderWindow subclasses) was tricky and fraught with issues.

Since QVTKOpenGLWidget uses QOpenGLWidget to create the OpenGL context, it uses QSurfaceFormat (set using QOpenGLWidget::setFormat or QSurfaceFormat::setDefaultFormat) to create appropriate window and context. You can use QVTKOpenGLWidget::copyToFormat to obtain a QSurfaceFormat appropriate for a vtkRenderWindow.

A typical usage for QVTKOpenGLWidget is as follows:

*
* // before initializing QApplication, set the default surface format.
* QSurfaceFormat::setDefaultFormat(QVTKOpenGLWidget::defaultFormat());
*
* QPointer<QVTKOpenGLWidget> widget = new QVTKOpenGLWidget(...);
* widget->SetRenderWindow(window.Get());
*
* // If using any of the standard view e.g. vtkContextView, then
* // you can do the following.
* view->SetRenderWindow(window.Get());
*
* // You can continue to use `window` as a regular vtkRenderWindow
* // including adding renderers, actors etc.
*
*

OpenGL Context

In QOpenGLWidget (superclass for QVTKOpenGLWidget), all rendering happens in a framebuffer object. Thus, care must be taken in the rendering code to never directly re-bind the default framebuffer i.e. ID 0.

QVTKOpenGLWidget creates an internal QOpenGLFramebufferObject, independent of the one created by superclass, for vtkRenderWindow to do the rendering in. This explicit double-buffering is useful in avoiding temporary back-buffer only renders done in VTK (e.g. when making selections) from destroying the results composed on screen.

Handling Render and Paint.

QWidget subclasses (including QOpenGLWidget and QVTKOpenGLWidget) display their contents on the screen in QWidget::paint in response to a paint event. QOpenGLWidget subclasses are expected to do OpenGL rendering in QOpenGLWidget::paintGL. QWidget can receive paint events for various reasons including widget getting focus/losing focus, some other widget on the UI e.g. QProgressBar in status bar updating, etc.

In VTK applications, any time the vtkRenderWindow needs to be updated to render a new result, one call vtkRenderWindow::Render on it. vtkRenderWindowInteractor set on the render window ensures that as interactions happen that affect the rendered result, it calls Render on the render window.

Since paint in Qt can be called more often then needed, we avoid potentially expensive vtkRenderWindow::Render calls each time that happens. Instead, QVTKOpenGLWidget relies on the VTK application calling vtkRenderWindow::Render on the render window when it needs to update the rendering. paintGL simply passes on the result rendered by the most render vtkRenderWindow::Render to Qt windowing system for composing on-screen.

There may still be occasions when we may have to render in paint for example if the window was resized or Qt had to recreate the OpenGL context. In those cases, QVTKOpenGLWidget::paintGL can request a render by calling QVTKOpenGLWidget::renderVTK.

Caveats

QVTKOpenGLWidget only supports OpenGL2 rendering backend. Thus is not available if VTK is built with VTK_RENDERING_BACKEND set to OpenGL.

QVTKOpenGLWidget is targeted for Qt version 5.5 and above.

Definition at line 123 of file QVTKOpenGLWidget.h.

Constructor & Destructor Documentation

QVTKOpenGLWidget::QVTKOpenGLWidget ( QWidget *  parent = Q_NULLPTR,
Qt::WindowFlags  f = Qt::WindowFlags() 
)
virtual QVTKOpenGLWidget::~QVTKOpenGLWidget ( )
virtual

Member Function Documentation

void QVTKOpenGLWidget::SetRenderWindow ( vtkGenericOpenGLRenderWindow win)

Get/Set the currently used vtkGenericOpenGLRenderWindow.

void QVTKOpenGLWidget::SetRenderWindow ( vtkRenderWindow win)

Get/Set the currently used vtkGenericOpenGLRenderWindow.

virtual vtkRenderWindow* QVTKOpenGLWidget::GetRenderWindow ( )
virtual

Get/Set the currently used vtkGenericOpenGLRenderWindow.

virtual QVTKInteractor* QVTKOpenGLWidget::GetInteractor ( )
virtual

Get the QVTKInteractor that was either created by default or set by the user.

static void QVTKOpenGLWidget::copyFromFormat ( const QSurfaceFormat &  format,
vtkRenderWindow win 
)
static

Sets up vtkRenderWindow ivars using QSurfaceFormat.

static void QVTKOpenGLWidget::copyToFormat ( vtkRenderWindow win,
QSurfaceFormat &  format 
)
static

Using the vtkRenderWindow, setup QSurfaceFormat.

static QSurfaceFormat QVTKOpenGLWidget::defaultFormat ( )
static

Returns a typical QSurfaceFormat suitable for most applications using QVTKOpenGLWidget.

Note that this is not the QSurfaceFormat that gets used if none is specified. That is set using QSurfaceFormat::setDefaultFormat.

virtual void QVTKOpenGLWidget::setEnableHiDPI ( bool  enable)
virtual

Enable or disable support for HiDPI displays.

void QVTKOpenGLWidget::mouseEvent ( QMouseEvent *  event)
signal

This signal will be emitted whenever a mouse event occurs within the QVTK window.

virtual void QVTKOpenGLWidget::cleanupContext ( )
protectedvirtualslot

Called as a response to QOpenGLContext::aboutToBeDestroyed.

This may be called anytime during the widget lifecycle. We need to release any OpenGL resources allocated in VTK work in this method.

bool QVTKOpenGLWidget::event ( QEvent *  evt)
protected
void QVTKOpenGLWidget::initializeGL ( )
protected
void QVTKOpenGLWidget::resizeGL ( int  w,
int  h 
)
protected
void QVTKOpenGLWidget::paintGL ( )
protected
void QVTKOpenGLWidget::moveEvent ( QMoveEvent *  event)
protected
void QVTKOpenGLWidget::mousePressEvent ( QMouseEvent *  event)
protected
void QVTKOpenGLWidget::mouseMoveEvent ( QMouseEvent *  event)
protected
void QVTKOpenGLWidget::mouseReleaseEvent ( QMouseEvent *  event)
protected
void QVTKOpenGLWidget::mouseDoubleClickEvent ( QMouseEvent *  event)
protected
void QVTKOpenGLWidget::requireRenderWindowInitialization ( )
protected

This method is called to indicate that vtkRenderWindow needs to reinitialize itself before the next render (done in QVTKOpenGLWidget::paintGL).

This is needed when the context gets recreated or the default FrameBufferObject gets recreated, for example.

virtual bool QVTKOpenGLWidget::renderVTK ( )
protectedvirtual

This method may be called in paintGL to request VTK to do a render i.e.

trigger render on the render window via its interactor.

It will return true if render (or an equivalent action) was performed to update the frame buffer made available to VTK for rendering with latest rendering.

Default implementation never returns false. However, subclasses can return false to indicate to QVTKOpenGLWidget that it cannot generate a reasonable image to be displayed in QVTKOpenGLWidget. In which case, the paintGL call will return leaving the defaultFramebufferObject untouched.

Since by default QOpenGLWidget::UpdateBehavior is set to QOpenGLWidget::PartialUpdate, this means whatever was rendered in the frame buffer in most recent successful call will be preserved, unless the widget was forced to recreate the FBO as a result of resize or screen change.

See Also
Section Handling Render and Paint..

Friends And Related Function Documentation

friend class QVTKOpenGLWidgetObserver
friend

Definition at line 255 of file QVTKOpenGLWidget.h.

Member Data Documentation

vtkSmartPointer<vtkGenericOpenGLRenderWindow> QVTKOpenGLWidget::RenderWindow
protected

Definition at line 236 of file QVTKOpenGLWidget.h.

QVTKInteractorAdapter* QVTKOpenGLWidget::InteractorAdaptor
protected

Definition at line 237 of file QVTKOpenGLWidget.h.

bool QVTKOpenGLWidget::EnableHiDPI
protected

Definition at line 239 of file QVTKOpenGLWidget.h.

int QVTKOpenGLWidget::OriginalDPI
protected

Definition at line 240 of file QVTKOpenGLWidget.h.


The documentation for this class was generated from the following file: