如何以编程方式在 qml 中呈现 vtk 项目？
How to render programmatically a vtk item in qml?
到目前为止，我了解到我们在 QML 中有两个线程，我们的主应用程序线程和我们的 "scene graph" 线程：http://doc.qt.io/qt-5/qtquick-visualcanvas-scenegraph.html
我已经在这个 link 的帮助下实现了我自己的 vtkQmlItem : http://doc.qt.io/qt-5/qtquick-scenegraph-openglunderqml-example.html
而且我注意到我的 vtkscene 仅在 qml 流发出 afterrendering 信号时呈现。
到目前为止，一切正常，工作完美，我可以看到我的 vtk 场景，甚至可以与之交互。
但我也想以编程方式渲染我的 vtk 场景，因为我想通过围绕 vtk 对象移动相机来制作动画。
直接调用 renderer->render() 显示有很多 vtk 错误，似乎不是执行此操作的好方法。
调用this->window()->update() 似乎将事件放入事件循环中，当我希望立即处理它时。我设法让它立即工作的唯一方法是使用 QApplication::processEvents()，这是我不喜欢的 hack 并且会喜欢另一个解决方案。
所以我不喜欢的工作解决方案的伪代码如下：
for (int i = 0; i < 50; i++)
{
ChangeCameraPosition(i); // Change the position and orientation of the vtk camera
this->window()->update();
QApplication::processEvents(); // The hack I don't like
QThread::msleep(500);
}
这个问题实际上有点复杂，如果过去几个月没有任何变化，VTK 中仍然不支持 QtQuick，这意味着没有简单的几行解决方案。您可以在 VTK/GUISupport/QtOpenGL/ 中找到对 QtWidgets 的支持 类 并将它们用作模板来派生对 qml 的支持。但我主要建议检查 this thread for a discussion about this topic.
关键是 QtQuick 为您试图在专用线程中呈现的 qml window 保留 openGL 上下文，它不会让其他任何东西获得该上下文。因此，为了从 VTK 渲染到它，您必须在该线程内进行。这意味着：
1) 创建您自己的 vtkRenderWindow 来覆盖 Render() 方法，以确保它发生在 qml 的渲染线程中。
2) 使渲染 window 渲染到 qtquick（QQuickFramebufferObject 的实例）提供的帧缓冲区对象中。
3) 将 vtk 的渲染信号与 qt 的渲染方法互连 -> 例如当vtk render window调用makeCurrent时，qt的渲染线程"wakes up".
这是我基于上面链接的 Taylor Braun-Jones' 模板的实现。它可能不完美，但对我有用（我删除了一些特定于我的应用程序的部分，因此它可能不会立即编译，但它应该会让你走上一些可行的解决方案）：
qmlVtk.h:
#include <vtkEventQtSlotConnect.h>
#include <vtkGenericOpenGLRenderWindow.h>
#include <vtkRenderer.h>
#include <QtQuick/QQuickFramebufferObject>
// Use the OpenGL API abstraction from Qt instead of from VTK because vtkgl.h
// and other Qt OpenGL-related headers do not play nice when included in the
// same compilation unit
#include <QOpenGLFunctions>
#include <qqmlapplicationengine.h>
class QVTKFramebufferObjectRenderer;
class QVTKInteractorAdapter;
class vtkInternalOpenGLRenderWindow;
class QVTKFramebufferObjectRenderer;
class QVTKFrameBufferObjectItem : public QQuickFramebufferObject
{
Q_OBJECT
public:
QVTKFrameBufferObjectItem(QQuickItem *parent = 0);
~QVTKFrameBufferObjectItem();
Renderer *createRenderer() const;
vtkSmartPointer<vtkInternalOpenGLRenderWindow> GetRenderWindow() const;
protected:
// Called once before the FBO is created for the first time. This method is
// called from render thread while the GUI thread is blocked.
virtual void init();
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_win;
QVTKInteractorAdapter* m_irenAdapter;
vtkSmartPointer<vtkEventQtSlotConnect> mConnect;
friend class QVTKFramebufferObjectRenderer;
// Convert the position of the event from openGL coordinate to native coordinate
QMouseEvent openGLToNative(QMouseEvent const& event);
virtual void mouseMoveEvent(QMouseEvent * event);
virtual void mousePressEvent(QMouseEvent * event);
virtual void mouseReleaseEvent(QMouseEvent * event);
virtual void mouseDoubleClickEvent(QMouseEvent * event);
virtual void wheelEvent(QWheelEvent *event);
virtual void keyPressEvent(QKeyEvent* event);
virtual void keyReleaseEvent(QKeyEvent* event);
virtual void focusInEvent(QFocusEvent * event);
virtual void focusOutEvent(QFocusEvent * event);
protected Q_SLOTS:
// slot to make this vtk render window current
virtual void MakeCurrent();
// slot called when vtk wants to know if the context is current
virtual void IsCurrent(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to start the render
virtual void Start();
// slot called when vtk wants to end the render
virtual void End();
// slot called when vtk wants to know if a window is direct
virtual void IsDirect(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to know if a window supports OpenGL
virtual void SupportsOpenGL(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
};
/// <summary>
/// An extension of vktGenericOpenGLRenderWindow to work with Qt.
/// Serves to write VTK-generated render calls to a framebuffer provided and maintained by Qt. It is meant to be used within Qt render loop, i.e. using Qt's render thread.
/// </summary>
/// <seealso cref="vtkGenericOpenGLRenderWindow" />
/// <seealso cref="QOpenGLFunctions" />
class vtkInternalOpenGLRenderWindow : public vtkGenericOpenGLRenderWindow, protected QOpenGLFunctions
{
public:
static vtkInternalOpenGLRenderWindow* New();
vtkTypeMacro(vtkInternalOpenGLRenderWindow, vtkGenericOpenGLRenderWindow)
virtual void OpenGLInitState();
// Override to use deferred rendering - Tell the QSG that we need to
// be rendered which will then, at the appropriate time, call
// InternalRender to do the actual OpenGL rendering.
virtual void Render();
// Do the actual OpenGL rendering
void InternalRender();
// Provides a convenient way to set the protected FBO ivars from an existing
// FBO that was created and owned by Qt's FBO abstraction class
// QOpenGLFramebufferObject
void SetFramebufferObject(QOpenGLFramebufferObject *fbo);
QVTKFramebufferObjectRenderer *QtParentRenderer;
protected:
vtkInternalOpenGLRenderWindow();
~vtkInternalOpenGLRenderWindow()
{
// Prevent superclass destructors from destroying the framebuffer object.
// QOpenGLFramebufferObject owns the FBO and manages it's lifecyle.
this->OffScreenRendering = 0;
}
};
qmlVtk.cpp:
#include "QVTKFramebufferObjectItem.h"
#include <QQuickFramebufferObject>
#include <QQuickWindow>
#include <QOpenGLFramebufferObject>
#include <QVTKInteractorAdapter.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkObjectFactory.h>
#include <vtkSmartPointer.h>
#include <vtkCamera.h>
#include <vtkProperty.h>
#include <qglfunctions.h>
class QVTKFramebufferObjectRenderer : public QQuickFramebufferObject::Renderer
{
friend class vtkInternalOpenGLRenderWindow;
public:
QVTKFramebufferObjectRenderer(vtkSmartPointer<vtkInternalOpenGLRenderWindow> rw) :
m_framebufferObject(0)
{
m_vtkRenderWindow = rw;
m_vtkRenderWindow->QtParentRenderer = this;
}
~QVTKFramebufferObjectRenderer()
{
m_vtkRenderWindow->QtParentRenderer = 0;
glFrontFace(GL_CCW); // restore default settings
}
virtual void synchronize(QQuickFramebufferObject * item)
{
// the first synchronize call - right before the the framebufferObject
// is created for the first time
if (!m_framebufferObject)
{
QVTKFrameBufferObjectItem *vtkItem = static_cast<QVTKFrameBufferObjectItem*>(item);
vtkItem->init();
}
}
virtual void render()
{
m_vtkRenderWindow->InternalRender(); // vtkXOpenGLRenderWindow renders the scene to the FBO
}
QOpenGLFramebufferObject *createFramebufferObject(const QSize &size)
{
QOpenGLFramebufferObjectFormat format;
format.setAttachment(QOpenGLFramebufferObject::Depth);
m_framebufferObject = new QOpenGLFramebufferObject(size, format);
m_vtkRenderWindow->SetFramebufferObject(m_framebufferObject);
return m_framebufferObject;
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_vtkRenderWindow;
QOpenGLFramebufferObject *m_framebufferObject;
};
vtkStandardNewMacro(vtkInternalOpenGLRenderWindow);
vtkInternalOpenGLRenderWindow::vtkInternalOpenGLRenderWindow() :
QtParentRenderer(0)
{
vtkOpenGLRenderWindow::OpenGLInitContext();
}
void vtkInternalOpenGLRenderWindow::OpenGLInitState()
{
this->MakeCurrent();
vtkOpenGLRenderWindow::OpenGLInitState();
// Before any of the gl* functions in QOpenGLFunctions are called for a
// given OpenGL context, an initialization must be run within that context
initializeOpenGLFunctions();
glFrontFace(GL_CW); // to compensate for the switched Y axis
}
void vtkInternalOpenGLRenderWindow::InternalRender()
{
vtkOpenGLRenderWindow::Render();
}
//
// vtkInternalOpenGLRenderWindow Definitions
//
void vtkInternalOpenGLRenderWindow::Render()
{
this->QtParentRenderer->update();
}
void vtkInternalOpenGLRenderWindow::SetFramebufferObject(QOpenGLFramebufferObject *fbo)
{
// QOpenGLFramebufferObject documentation states that "The color render
// buffer or texture will have the specified internal format, and will
// be bound to the GL_COLOR_ATTACHMENT0 attachment in the framebuffer
// object"
this->BackLeftBuffer = this->FrontLeftBuffer = this->BackBuffer = this->FrontBuffer =
static_cast<unsigned int>(GL_COLOR_ATTACHMENT0);
// Save GL objects by static casting to standard C types. GL* types
// are not allowed in VTK header files.
QSize fboSize = fbo->size();
this->Size[0] = fboSize.width();
this->Size[1] = fboSize.height();
this->NumberOfFrameBuffers = 1;
this->FrameBufferObject = static_cast<unsigned int>(fbo->handle());
this->DepthRenderBufferObject = 0; // static_cast<unsigned int>(depthRenderBufferObject);
this->TextureObjects[0] = static_cast<unsigned int>(fbo->texture());
this->OffScreenRendering = 1;
this->OffScreenUseFrameBuffer = 1;
this->Modified();
}
void QVTKFrameBufferObjectItem::Start()
{
m_win->OpenGLInitState();
}
void QVTKFrameBufferObjectItem::End()
{
}
void QVTKFrameBufferObjectItem::MakeCurrent()
{
this->window()->openglContext()->makeCurrent(this->window());
}
void QVTKFrameBufferObjectItem::IsCurrent(vtkObject*, unsigned long, void*, void* call_data)
{
bool* ptr = reinterpret_cast<bool*>(call_data);
*ptr = this->window()->openglContext();
}
void QVTKFrameBufferObjectItem::IsDirect(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::fromSurfaceFormat(this->window()->openglContext()->format()).directRendering();
}
void QVTKFrameBufferObjectItem::SupportsOpenGL(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::hasOpenGL();
}
QVTKFrameBufferObjectItem::QVTKFrameBufferObjectItem(QQuickItem *parent) : QQuickFramebufferObject(parent)
{
setAcceptedMouseButtons(Qt::AllButtons);
m_irenAdapter = new QVTKInteractorAdapter(this);
m_win = vtkSmartPointer<vtkInternalOpenGLRenderWindow>::New();
// make a connection between the vtk signals and qt slots so that an initialized and madeCurrent opengl context is given to the vtk
// we probably need only the Start(), MakeCurrent() and End() one, but just to be sure...
mConnect = vtkSmartPointer<vtkEventQtSlotConnect>::New();
mConnect->Connect(m_win, vtkCommand::WindowMakeCurrentEvent, this, SLOT(MakeCurrent()));
mConnect->Connect(m_win, vtkCommand::WindowIsCurrentEvent, this, SLOT(IsCurrent(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::StartEvent, this, SLOT(Start()));
mConnect->Connect(m_win, vtkCommand::EndEvent, this, SLOT(End()));
mConnect->Connect(m_win, vtkCommand::WindowIsDirectEvent, this, SLOT(IsDirect(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::WindowSupportsOpenGLEvent, this, SLOT(SupportsOpenGL(vtkObject*, unsigned long, void*, void*)));
}
QVTKFrameBufferObjectItem::~QVTKFrameBufferObjectItem()
{
mConnect->Disconnect(); // disconnect all slots
if (m_irenAdapter)
delete m_irenAdapter;
}
QQuickFramebufferObject::Renderer *QVTKFrameBufferObjectItem::createRenderer() const
{
return new QVTKFramebufferObjectRenderer(m_win);
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> QVTKFrameBufferObjectItem::GetRenderWindow() const
{
return m_win;
}
void QVTKFrameBufferObjectItem::init()
{
}
// theoretically not needed now - the Y is being flipped in render and devicePixelRatio will almost always be = 1 on a PC anyway...but lets keep it to be sure
QMouseEvent QVTKFrameBufferObjectItem::openGLToNative(QMouseEvent const& event)
{
QPointF localPos(event.localPos());
localPos.setX(localPos.x() * window()->devicePixelRatio());
localPos.setY(localPos.y() * window()->devicePixelRatio());
QMouseEvent nativeEvent(event.type(), localPos, event.button(), event.buttons(), event.modifiers());
return nativeEvent;
}
void QVTKFrameBufferObjectItem::mouseMoveEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mousePressEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mouseReleaseEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::wheelEvent(QWheelEvent *event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyPressEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyReleaseEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusInEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusOutEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
要使用它，请在您的 qml 表单中定义一个帧缓冲区实例，并将其拉伸到您要渲染到的 window，例如像这样（假设您在 qml 中将 QVTKFrameBufferObjectItem 注册为 QVTKFrameBuffer，例如像这样 qmlRegisterType<QVTKFrameBufferObjectItem>("VtkQuick", 1, 0, "QVTKFrameBuffer");）：
import VtkQuick 1.0
QVTKFrameBuffer
{
id: renderBuffer
anchors.fill : parent
Component.onCompleted :
{
myCppDisplay.framebuffer = renderBuffer // tell the c++ side of your app that this is the framebuffer into which it should render
}
}
然后您可以使用通过 myCppDisplay.framebuffer.GetRenderWindow() 获得的 vtkRenderWindow，如果您渲染到 vtk-managed window，您可以使用与使用任何其他 vtkRenderWindow 相同的方式，即您可以将 vtkRenderer 分配给它，将演员分配给该渲染器，根据需要调用 theWindow.Render() ，它将全部渲染到您为其分配帧缓冲区的 qml 组件中。
两个注意事项：1）vtk和qt使用不同的坐标系，你需要翻转y-coordinate...我是通过给相机分配一个比例变换来实现的，但是有很多其他方法：
vtkSmartPointer<vtkTransform> scale = vtkSmartPointer<vtkTransform>::New();
scale->Scale(1, -1, 1);
renderer->GetActiveCamera()->SetUserTransform(scale);
2) 一旦你开始使用多线程，事情就会变得非常棘手——你必须确保你没有尝试在两个不同的线程中渲染，因为它们会竞争一个 QtQuick 的渲染线程。这不仅仅意味着不并行调用 renderWindow.Render() - 这很容易避免 - 但你必须意识到 qt 线程也用于渲染 GUI，所以你可能会以这种方式遇到麻烦（更新进行 VTK 渲染时的 GUI）。
对于使用 Qt QuickControls 2 和 VTK 8 寻找解决方案的人，您可以在此存储库中找到一个工作示例 https://github.com/nicanor-romero/QtVtk，并在自述文件中提供构建说明。
到目前为止，我了解到我们在 QML 中有两个线程，我们的主应用程序线程和我们的 "scene graph" 线程：http://doc.qt.io/qt-5/qtquick-visualcanvas-scenegraph.html
我已经在这个 link 的帮助下实现了我自己的 vtkQmlItem : http://doc.qt.io/qt-5/qtquick-scenegraph-openglunderqml-example.html
而且我注意到我的 vtkscene 仅在 qml 流发出 afterrendering 信号时呈现。
到目前为止，一切正常，工作完美，我可以看到我的 vtk 场景，甚至可以与之交互。
但我也想以编程方式渲染我的 vtk 场景，因为我想通过围绕 vtk 对象移动相机来制作动画。
直接调用 renderer->render() 显示有很多 vtk 错误，似乎不是执行此操作的好方法。
调用this->window()->update() 似乎将事件放入事件循环中，当我希望立即处理它时。我设法让它立即工作的唯一方法是使用 QApplication::processEvents()，这是我不喜欢的 hack 并且会喜欢另一个解决方案。
所以我不喜欢的工作解决方案的伪代码如下：
for (int i = 0; i < 50; i++)
{
ChangeCameraPosition(i); // Change the position and orientation of the vtk camera
this->window()->update();
QApplication::processEvents(); // The hack I don't like
QThread::msleep(500);
}
这个问题实际上有点复杂，如果过去几个月没有任何变化，VTK 中仍然不支持 QtQuick，这意味着没有简单的几行解决方案。您可以在 VTK/GUISupport/QtOpenGL/ 中找到对 QtWidgets 的支持 类 并将它们用作模板来派生对 qml 的支持。但我主要建议检查 this thread for a discussion about this topic.
关键是 QtQuick 为您试图在专用线程中呈现的 qml window 保留 openGL 上下文，它不会让其他任何东西获得该上下文。因此，为了从 VTK 渲染到它，您必须在该线程内进行。这意味着：
1) 创建您自己的 vtkRenderWindow 来覆盖 Render() 方法，以确保它发生在 qml 的渲染线程中。
2) 使渲染 window 渲染到 qtquick（QQuickFramebufferObject 的实例）提供的帧缓冲区对象中。
3) 将 vtk 的渲染信号与 qt 的渲染方法互连 -> 例如当vtk render window调用makeCurrent时，qt的渲染线程"wakes up".
这是我基于上面链接的 Taylor Braun-Jones' 模板的实现。它可能不完美，但对我有用（我删除了一些特定于我的应用程序的部分，因此它可能不会立即编译，但它应该会让你走上一些可行的解决方案）：
qmlVtk.h:
#include <vtkEventQtSlotConnect.h>
#include <vtkGenericOpenGLRenderWindow.h>
#include <vtkRenderer.h>
#include <QtQuick/QQuickFramebufferObject>
// Use the OpenGL API abstraction from Qt instead of from VTK because vtkgl.h
// and other Qt OpenGL-related headers do not play nice when included in the
// same compilation unit
#include <QOpenGLFunctions>
#include <qqmlapplicationengine.h>
class QVTKFramebufferObjectRenderer;
class QVTKInteractorAdapter;
class vtkInternalOpenGLRenderWindow;
class QVTKFramebufferObjectRenderer;
class QVTKFrameBufferObjectItem : public QQuickFramebufferObject
{
Q_OBJECT
public:
QVTKFrameBufferObjectItem(QQuickItem *parent = 0);
~QVTKFrameBufferObjectItem();
Renderer *createRenderer() const;
vtkSmartPointer<vtkInternalOpenGLRenderWindow> GetRenderWindow() const;
protected:
// Called once before the FBO is created for the first time. This method is
// called from render thread while the GUI thread is blocked.
virtual void init();
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_win;
QVTKInteractorAdapter* m_irenAdapter;
vtkSmartPointer<vtkEventQtSlotConnect> mConnect;
friend class QVTKFramebufferObjectRenderer;
// Convert the position of the event from openGL coordinate to native coordinate
QMouseEvent openGLToNative(QMouseEvent const& event);
virtual void mouseMoveEvent(QMouseEvent * event);
virtual void mousePressEvent(QMouseEvent * event);
virtual void mouseReleaseEvent(QMouseEvent * event);
virtual void mouseDoubleClickEvent(QMouseEvent * event);
virtual void wheelEvent(QWheelEvent *event);
virtual void keyPressEvent(QKeyEvent* event);
virtual void keyReleaseEvent(QKeyEvent* event);
virtual void focusInEvent(QFocusEvent * event);
virtual void focusOutEvent(QFocusEvent * event);
protected Q_SLOTS:
// slot to make this vtk render window current
virtual void MakeCurrent();
// slot called when vtk wants to know if the context is current
virtual void IsCurrent(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to start the render
virtual void Start();
// slot called when vtk wants to end the render
virtual void End();
// slot called when vtk wants to know if a window is direct
virtual void IsDirect(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
// slot called when vtk wants to know if a window supports OpenGL
virtual void SupportsOpenGL(vtkObject* caller, unsigned long vtk_event, void* client_data, void* call_data);
};
/// <summary>
/// An extension of vktGenericOpenGLRenderWindow to work with Qt.
/// Serves to write VTK-generated render calls to a framebuffer provided and maintained by Qt. It is meant to be used within Qt render loop, i.e. using Qt's render thread.
/// </summary>
/// <seealso cref="vtkGenericOpenGLRenderWindow" />
/// <seealso cref="QOpenGLFunctions" />
class vtkInternalOpenGLRenderWindow : public vtkGenericOpenGLRenderWindow, protected QOpenGLFunctions
{
public:
static vtkInternalOpenGLRenderWindow* New();
vtkTypeMacro(vtkInternalOpenGLRenderWindow, vtkGenericOpenGLRenderWindow)
virtual void OpenGLInitState();
// Override to use deferred rendering - Tell the QSG that we need to
// be rendered which will then, at the appropriate time, call
// InternalRender to do the actual OpenGL rendering.
virtual void Render();
// Do the actual OpenGL rendering
void InternalRender();
// Provides a convenient way to set the protected FBO ivars from an existing
// FBO that was created and owned by Qt's FBO abstraction class
// QOpenGLFramebufferObject
void SetFramebufferObject(QOpenGLFramebufferObject *fbo);
QVTKFramebufferObjectRenderer *QtParentRenderer;
protected:
vtkInternalOpenGLRenderWindow();
~vtkInternalOpenGLRenderWindow()
{
// Prevent superclass destructors from destroying the framebuffer object.
// QOpenGLFramebufferObject owns the FBO and manages it's lifecyle.
this->OffScreenRendering = 0;
}
};
qmlVtk.cpp:
#include "QVTKFramebufferObjectItem.h"
#include <QQuickFramebufferObject>
#include <QQuickWindow>
#include <QOpenGLFramebufferObject>
#include <QVTKInteractorAdapter.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkObjectFactory.h>
#include <vtkSmartPointer.h>
#include <vtkCamera.h>
#include <vtkProperty.h>
#include <qglfunctions.h>
class QVTKFramebufferObjectRenderer : public QQuickFramebufferObject::Renderer
{
friend class vtkInternalOpenGLRenderWindow;
public:
QVTKFramebufferObjectRenderer(vtkSmartPointer<vtkInternalOpenGLRenderWindow> rw) :
m_framebufferObject(0)
{
m_vtkRenderWindow = rw;
m_vtkRenderWindow->QtParentRenderer = this;
}
~QVTKFramebufferObjectRenderer()
{
m_vtkRenderWindow->QtParentRenderer = 0;
glFrontFace(GL_CCW); // restore default settings
}
virtual void synchronize(QQuickFramebufferObject * item)
{
// the first synchronize call - right before the the framebufferObject
// is created for the first time
if (!m_framebufferObject)
{
QVTKFrameBufferObjectItem *vtkItem = static_cast<QVTKFrameBufferObjectItem*>(item);
vtkItem->init();
}
}
virtual void render()
{
m_vtkRenderWindow->InternalRender(); // vtkXOpenGLRenderWindow renders the scene to the FBO
}
QOpenGLFramebufferObject *createFramebufferObject(const QSize &size)
{
QOpenGLFramebufferObjectFormat format;
format.setAttachment(QOpenGLFramebufferObject::Depth);
m_framebufferObject = new QOpenGLFramebufferObject(size, format);
m_vtkRenderWindow->SetFramebufferObject(m_framebufferObject);
return m_framebufferObject;
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> m_vtkRenderWindow;
QOpenGLFramebufferObject *m_framebufferObject;
};
vtkStandardNewMacro(vtkInternalOpenGLRenderWindow);
vtkInternalOpenGLRenderWindow::vtkInternalOpenGLRenderWindow() :
QtParentRenderer(0)
{
vtkOpenGLRenderWindow::OpenGLInitContext();
}
void vtkInternalOpenGLRenderWindow::OpenGLInitState()
{
this->MakeCurrent();
vtkOpenGLRenderWindow::OpenGLInitState();
// Before any of the gl* functions in QOpenGLFunctions are called for a
// given OpenGL context, an initialization must be run within that context
initializeOpenGLFunctions();
glFrontFace(GL_CW); // to compensate for the switched Y axis
}
void vtkInternalOpenGLRenderWindow::InternalRender()
{
vtkOpenGLRenderWindow::Render();
}
//
// vtkInternalOpenGLRenderWindow Definitions
//
void vtkInternalOpenGLRenderWindow::Render()
{
this->QtParentRenderer->update();
}
void vtkInternalOpenGLRenderWindow::SetFramebufferObject(QOpenGLFramebufferObject *fbo)
{
// QOpenGLFramebufferObject documentation states that "The color render
// buffer or texture will have the specified internal format, and will
// be bound to the GL_COLOR_ATTACHMENT0 attachment in the framebuffer
// object"
this->BackLeftBuffer = this->FrontLeftBuffer = this->BackBuffer = this->FrontBuffer =
static_cast<unsigned int>(GL_COLOR_ATTACHMENT0);
// Save GL objects by static casting to standard C types. GL* types
// are not allowed in VTK header files.
QSize fboSize = fbo->size();
this->Size[0] = fboSize.width();
this->Size[1] = fboSize.height();
this->NumberOfFrameBuffers = 1;
this->FrameBufferObject = static_cast<unsigned int>(fbo->handle());
this->DepthRenderBufferObject = 0; // static_cast<unsigned int>(depthRenderBufferObject);
this->TextureObjects[0] = static_cast<unsigned int>(fbo->texture());
this->OffScreenRendering = 1;
this->OffScreenUseFrameBuffer = 1;
this->Modified();
}
void QVTKFrameBufferObjectItem::Start()
{
m_win->OpenGLInitState();
}
void QVTKFrameBufferObjectItem::End()
{
}
void QVTKFrameBufferObjectItem::MakeCurrent()
{
this->window()->openglContext()->makeCurrent(this->window());
}
void QVTKFrameBufferObjectItem::IsCurrent(vtkObject*, unsigned long, void*, void* call_data)
{
bool* ptr = reinterpret_cast<bool*>(call_data);
*ptr = this->window()->openglContext();
}
void QVTKFrameBufferObjectItem::IsDirect(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::fromSurfaceFormat(this->window()->openglContext()->format()).directRendering();
}
void QVTKFrameBufferObjectItem::SupportsOpenGL(vtkObject*, unsigned long, void*, void* call_data)
{
int* ptr = reinterpret_cast<int*>(call_data);
*ptr = QGLFormat::hasOpenGL();
}
QVTKFrameBufferObjectItem::QVTKFrameBufferObjectItem(QQuickItem *parent) : QQuickFramebufferObject(parent)
{
setAcceptedMouseButtons(Qt::AllButtons);
m_irenAdapter = new QVTKInteractorAdapter(this);
m_win = vtkSmartPointer<vtkInternalOpenGLRenderWindow>::New();
// make a connection between the vtk signals and qt slots so that an initialized and madeCurrent opengl context is given to the vtk
// we probably need only the Start(), MakeCurrent() and End() one, but just to be sure...
mConnect = vtkSmartPointer<vtkEventQtSlotConnect>::New();
mConnect->Connect(m_win, vtkCommand::WindowMakeCurrentEvent, this, SLOT(MakeCurrent()));
mConnect->Connect(m_win, vtkCommand::WindowIsCurrentEvent, this, SLOT(IsCurrent(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::StartEvent, this, SLOT(Start()));
mConnect->Connect(m_win, vtkCommand::EndEvent, this, SLOT(End()));
mConnect->Connect(m_win, vtkCommand::WindowIsDirectEvent, this, SLOT(IsDirect(vtkObject*, unsigned long, void*, void*)));
mConnect->Connect(m_win, vtkCommand::WindowSupportsOpenGLEvent, this, SLOT(SupportsOpenGL(vtkObject*, unsigned long, void*, void*)));
}
QVTKFrameBufferObjectItem::~QVTKFrameBufferObjectItem()
{
mConnect->Disconnect(); // disconnect all slots
if (m_irenAdapter)
delete m_irenAdapter;
}
QQuickFramebufferObject::Renderer *QVTKFrameBufferObjectItem::createRenderer() const
{
return new QVTKFramebufferObjectRenderer(m_win);
}
vtkSmartPointer<vtkInternalOpenGLRenderWindow> QVTKFrameBufferObjectItem::GetRenderWindow() const
{
return m_win;
}
void QVTKFrameBufferObjectItem::init()
{
}
// theoretically not needed now - the Y is being flipped in render and devicePixelRatio will almost always be = 1 on a PC anyway...but lets keep it to be sure
QMouseEvent QVTKFrameBufferObjectItem::openGLToNative(QMouseEvent const& event)
{
QPointF localPos(event.localPos());
localPos.setX(localPos.x() * window()->devicePixelRatio());
localPos.setY(localPos.y() * window()->devicePixelRatio());
QMouseEvent nativeEvent(event.type(), localPos, event.button(), event.buttons(), event.modifiers());
return nativeEvent;
}
void QVTKFrameBufferObjectItem::mouseMoveEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mousePressEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::mouseReleaseEvent(QMouseEvent * event)
{
m_win->GetInteractor()->SetSize(this->width(), this->height());
QMouseEvent nativeEvent = openGLToNative(*event);
m_irenAdapter->ProcessEvent(&nativeEvent, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::wheelEvent(QWheelEvent *event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyPressEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::keyReleaseEvent(QKeyEvent* event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusInEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
void QVTKFrameBufferObjectItem::focusOutEvent(QFocusEvent * event)
{
m_irenAdapter->ProcessEvent(event, this->m_win->GetInteractor());
}
要使用它，请在您的 qml 表单中定义一个帧缓冲区实例，并将其拉伸到您要渲染到的 window，例如像这样（假设您在 qml 中将 QVTKFrameBufferObjectItem 注册为 QVTKFrameBuffer，例如像这样 qmlRegisterType<QVTKFrameBufferObjectItem>("VtkQuick", 1, 0, "QVTKFrameBuffer");）：
import VtkQuick 1.0
QVTKFrameBuffer
{
id: renderBuffer
anchors.fill : parent
Component.onCompleted :
{
myCppDisplay.framebuffer = renderBuffer // tell the c++ side of your app that this is the framebuffer into which it should render
}
}
然后您可以使用通过 myCppDisplay.framebuffer.GetRenderWindow() 获得的 vtkRenderWindow，如果您渲染到 vtk-managed window，您可以使用与使用任何其他 vtkRenderWindow 相同的方式，即您可以将 vtkRenderer 分配给它，将演员分配给该渲染器，根据需要调用 theWindow.Render() ，它将全部渲染到您为其分配帧缓冲区的 qml 组件中。
两个注意事项：1）vtk和qt使用不同的坐标系，你需要翻转y-coordinate...我是通过给相机分配一个比例变换来实现的，但是有很多其他方法：
vtkSmartPointer<vtkTransform> scale = vtkSmartPointer<vtkTransform>::New();
scale->Scale(1, -1, 1);
renderer->GetActiveCamera()->SetUserTransform(scale);
2) 一旦你开始使用多线程，事情就会变得非常棘手——你必须确保你没有尝试在两个不同的线程中渲染，因为它们会竞争一个 QtQuick 的渲染线程。这不仅仅意味着不并行调用 renderWindow.Render() - 这很容易避免 - 但你必须意识到 qt 线程也用于渲染 GUI，所以你可能会以这种方式遇到麻烦（更新进行 VTK 渲染时的 GUI）。
对于使用 Qt QuickControls 2 和 VTK 8 寻找解决方案的人，您可以在此存储库中找到一个工作示例 https://github.com/nicanor-romero/QtVtk，并在自述文件中提供构建说明。