I want to create an OGL data processor using QGLFunctions shaders and framebuffers. I don't need any widgets. But to create valid Shader and framebuffer instances, I need a valid QGLContext with support for the appropriate glExtensions.
With zero context, of course, nothing works. With context of zero QPaintDevice too. With Qpixmap as device it creates a valid context, but it lacks glExtensions for Shader and framebuffer.
#include <QGLFramebufferObject>
#include <QGLShaderProgram>
#include <QtOpenGL/QGLFunctions>
// ...
void GLProcessor::init()
{
auto format = QGLFormat::defaultFormat();
if (!context()){
m_context = new QGLContext(format, new QPixmap(1, 1));
bool ok = m_context->create();
qDebug() << "CREATING CONTEXT "<< ok;
Q_ASSERT(context()->isValid());
}
context()->makeCurrent();
initializeGLFunctions(context());
m_binFBO = new QGLFramebufferObject(lowsize ,lowsize ,QGLFramebufferObject::NoAttachment, GL_TEXTURE_2D, GL_RED);
m_outFBO = new QGLFramebufferObject(lowsize ,1 ,QGLFramebufferObject::NoAttachment, GL_TEXTURE_2D, GL_RED);
setupShaders();
// ...
}
There is an option, of course, to do as always is to get the context from the QGLWidget and hide it. But somehow inelegant. PS CUDA, OpenCL, AMP and so on I don't need. For my tasks need OpenGL.
How do I use shaders and framebuffers in qt4 without creating a QGLWidget?
Related
I'm trying to print multiple table (qtablewidget) objects in single pdf using qt.
I can print one table, using the code provided in(https://forum.qt.io/topic/80501/qpainter-howto-draw-table/7)
QPixmap pix(widget->size());
QPainter painter(&pix);
widget->render(&painter);
painter.end();
QPrinter printer(QPrinter::HighResolution);
printer.setOrientation(QPrinter::Landscape);
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setPaperSize(QPrinter::A4);
printer.setOutputFileName("test.pdf"); // will be in build folder
painter.begin(&printer);
painter.drawPixmap(0, 0, pix);
painter.end();
However, if I try to print multiple tables, the code fails. If I create multiple QPainters, qt just outputs multiple pdfs, with one table in each pdf. I'm trying to do it using one QPainter and multiple QPixmaps, but no success so far.
Would anyone please let me know how I can get around it?
Any help would be appreciated
Regards,
How does the code fail? The below should work (I didn't test it). Note the absence of manual object lifetime management: let the compiler do it for you. A QPainter is a proper C++ class and knows how to release its resources without having to manually invoke QPainter::end().
void printWidgets(QWidgetList widgets) {
QVector<QPixmap> pixmaps;
for (auto *w : widgets) {
QPixmap pix(w->size());
QPainter painter(pix);
w->render(&painter);
pixmaps.push_back(pix);
}
QPrinter printer(QPrinter::HighResolution);
printer.setOrientation(QPrinter::Landscape);
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setPaperSize(QPrinter::A4);
printer.setOutputFileName("test.pdf"); // will be in build folder
QPainter painter(&printer);
QPoint pos;
for (auto &pix : qAsConst(pixmaps)) {
painter.drawPixmap(pos, pix);
pos.ry() += pix.height(); // stack the output vertically
}
}
I currently am writing some unittests for OpenCL kernels and need to create a context.
As I am not after performance it does not matter to me which device is running the kernel.
So I want to create the context with as little restrictions as possible and thought of this code:
#define __CL_ENABLE_EXCEPTIONS
#include <CL/cl.hpp>
#include <iostream>
int main() {
try {
cl::Context context(CL_DEVICE_TYPE_ALL);
}catch(const cl::Error &err) {
std::cerr << "Caught cl::Error (" << err.what() << "): " << err.err() << "\n";
}
}
Which returns
Caught cl::Error (clCreateContextFromType): -32
-32 is CL_INVALID_PLATFORM and the documentation of clCreateContextFromType says:
CL_INVALID_PLATFORM if properties is NULL and no platform could be selected or if platform value specified in properties is not a valid platform.
As I have not provided any properties they are of course NULL.
Why can't any platform be selected?
I also have tried CL_DEVICE_TYPE_DEFAULT with the same result.
Here is a list of my platform and device that were detected:
NVIDIA CUDA
(GPU) GeForce GTX 560
As a side node: Specifying the platform in the properties works as intented.
I tried your code, using CL_DEVICE_TYPE_ALL and it worked on my setup. I'm not sure why it's not working on yours...
As a workaround, maybe you could do something like this:
// Get all available platforms
std::vector<cl::Platform> platforms;
cl::Platform::get(&platforms);
// Pick the first and get all available devices
std::vector<cl::Device> devices;
platforms[0].getDevices(CL_DEVICE_TYPE_ALL, &devices);
// Create a context on the first device, whatever it is
cl::Context context(devices[0]);
cl::Context context(cl_device_type) is calling the complete constructor with default parameters:
cl::Context::Context(cl_device_type type,
cl_context_properties * properties = NULL,
void(CL_CALLBACK *notifyFptr)(const char *,const void *,::size_t,void *) = NULL,
void * data = NULL,
cl_int * err = NULL
)
Witch is only a wrapper of C++ to the underlying clCreateContextFromType().
This function allows that a NULL pointer is passed as a property, but then, the platform selection is implementation dependent. And it looks like in your case it does not default to nVIDIA platform.
You will have to pass some info to the constructor I'm afraid....
Small version of my question
In a QGraphicsItem::paint() function I have a QGLFrameBufferObject. How do I get it on the paintdevice of the painter that is passed as an argument? (provided that the QGraphicsItem is in a scene that is being rendered by a QGraphicsView that has a QGLWidget as viewport => painter is using opengl engine)
QGraphicsItem::paint(QPainter* painter, ...)
{
QGLFramebufferObject fbo;
QPainter p(fbo);
... // Some painting code on the fbo
p.end();
// What now? How to get the fbo content drawn on the painter?
}
I have looked at the framebufferobject and pbuffer examples provided with Qt. There the fbo/pbuffer is drawn in a QGLWidget using custom opengl code. Is it possible to do the same thing within a paint() method of a QGraphicsItem and take the position of the QGraphisItem in the scene/view into account?
Big version of my question
Situation sketch
I have a QGraphicsScene. In it is an item that has a QGraphicsEffect (own implementation by overriding draw() from QGraphicsEffect). The scene is rendered by a QGraphicsView that has a QGLWidget as viewport.
In the QGraphicsEffect::draw(QPainter*) I have to generate some pixmap which I then want to draw using the painter provided (the painter has the QGLWidget as paintdevice). Constructing the pixmap is a combination of some draw calls and I want these to be done in hardware.
Simplified example: (I don't call sourcepixmap in my draw() method as it is not needed to demonstrate my problem)
class OwnGraphicsEffect: public QGraphicsEffect
{
virtual void draw(QPainter* painter);
}
void OwnGraphicsEffect::draw(QPainter* painter)
{
QRect rect(0,0,100,100);
QGLPixelBuffer pbuffer(rect.size(), QGLFormat(QGL::Rgba));
QPainter p(pbuffer);
p.fillRect(rect, Qt::transparent);
p.end();
painter->drawImage(QPoint(0,0), pbuffer->toImage(),rect);
}
Actual problem
My concerns are with the last line of my code: pbuffer->toImage(). I don't want to use this. I don't want to have a QImage conversion because of performance reasons. Is there a way to get a pixmap from my glpixelbuffer and then use painter->drawpixmap()?
I know I also can copy the pbuffer to a texture by using :
GLuint dynamicTexture = pbuffer.generateDynamicTexture();
pbuffer.updateDynamicTexture(dynamicTexture);
but I have no idea on how to get this texture onto the "painter".
Extending leemes' answer, here is a solution which can also handle multisample framebuffer objects.
First, if you want to draw on a QGLWidget, you can simply use the OpenGL commands
leemes suggested in his answer. Note that there is a ready-to-use drawTexture()
command available, which simplifies this code to the following:
void Widget::drawFBO(QPainter &painter, QGLFramebufferObject &fbo, QRect target)
{
painter.beginNativePainting();
drawTexture(target, fbo.texture());
painter.endNativePainting();
}
To draw multisample FBOs, you can convert them into non-multisample ones
using QGLFramebufferObject::blitFramebuffer (Note that not every hardware
/ driver combination supports this feature!):
if(fbo.format().samples() > 1)
{
QGLFramebufferObject texture(fbo.size()); // the non-multisampled fbo
QGLFramebufferObject::blitFramebuffer(
&texture, QRect(0, 0, fbo.width(), fbo.height()),
&fbo, QRect(0, 0, fbo.width(), fbo.height()));
drawTexture(targetRect, texture.texture());
}
else
drawTexture(targetRect, fbo.texture());
However, as far as I know, you can't draw using OpenGL commands on a non-OpenGL context.
For this, you first need to convert the framebuffer to a (software) image, like
a QImage using fbo.toImage() and draw this using your QPainter instead of the
fbo directly.
I think I figured it out. I use the QPainter::beginNativePainting() to mix OpenGL commands in a paintEvent:
void Widget::drawFBO(QPainter &painter, QGLFramebufferObject &fbo, QRect target)
{
painter.beginNativePainting();
glEnable(GL_TEXTURE_2D);
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
glBindTexture(GL_TEXTURE_2D, fbo.texture());
glBegin(GL_QUADS);
glTexCoord2d(0.0,1.0); glVertex2d(target.left(), target.top());
glTexCoord2d(1.0,1.0); glVertex2d(target.right() + 1, target.top());
glTexCoord2d(1.0,0.0); glVertex2d(target.right() + 1, target.bottom() + 1);
glTexCoord2d(0.0,0.0); glVertex2d(target.left(), target.bottom() + 1);
glEnd();
painter.endNativePainting();
}
I hope this will also work in the paintEvent of a QGraphicsItem (where the QGraphicsView uses a QGLWidget as the viewport), since I only tested it in QGLWidget::paintEvent directly.
There is, however, still the following problem: I don't know how to paint a multisample framebuffer. The documentation of QGLFramebufferObject::texture() says:
If a multisample framebuffer object is used then the value returned from this function will be invalid.
I'm trying to make an app using Kinect (OpenNI), processing the image (OpenCV) with a GUI.
I tested de OpenNI+OpenCV and OpenCV+Qt
Normally when we use OpenCV+Qt we can make a QWidget to show the content of the camera (VideoCapture) .. Capture a frame and update this querying for new frames to device.
With OpenNI and OpenCV i see examples using a for cycle to pull data from Kinect Sensors (image, depth) , but i don't know how to make this pulling routing mora straightforward. I mean, similar to the OpenCV frame querying.
The idea is embed in a QWidget the images captured from Kinect. The QWidget will have (for now) 2 buttons "Start Kinect" and "Quit" ..and below the Painting section to show the data captured.
Any thoughs?
You can try the QTimer class to query the kinect at fixed time intervals. In my application I use the code below.
void UpperBodyGestures::refreshUsingTimer()
{
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(MainEventFunction()));
timer->start(30);
}
void UpperBodyGestures::on_pushButton_Kinect_clicked()
{
InitKinect();
ui.pushButton_Kinect->setEnabled(false);
}
// modify the main function to call refreshUsingTimer function
UpperBodyGestures w;
w.show();
w.refreshUsingTimer();
return a.exec();
Then to query the frame you can use the label widget. I'm posting an example code below:
// Query the depth data from Openni
const XnDepthPixel* pDepth = depthMD.Data();
// Convert it to opencv for manipulation etc
cv::Mat DepthBuf(480,640,CV_16UC1,(unsigned char*)g_Depth);
// Normalize Depth image to 0-255 range (cant remember max range number so assuming it as 10k)
DepthBuf = DepthBuf / 10000 *255;
DepthBuf.convertTo(DepthBuf,CV_8UC1);
// Convert opencv image to a Qimage object
QImage qimage((const unsigned char*)DepthBuf.data, DepthBuf.size().width, DepthBuf.size().height, DepthBuf.step, QImage::Format_RGB888);
// Display the Qimage in the defined mylabel object
ui.myLabel->setPixmap(pixmap.fromImage(qimage,0).scaled(QSize(300,300), Qt::KeepAspectRatio, Qt::FastTransformation));
I found a rather disguting behaviour of glDeleteTexture, deleteing only parts of the aqcuired memory (GPU side and as Textures get saved back for the sake of speed in RAM), which in my case, is a showstopper bug, my program eating up all memory.
I don't want/require you to read all of the code, it's just a demo, I'd rather know how to actually use glDeleteTextures so it does not leak any memory.
The example code requires Qt 4.5 or later to compile:
glleak.pro
QT += opengl
SOURCES += main.cpp \
glleak.cpp
HEADERS += glleak.h
main.cpp
#include <QtOpenGL>
#include <QtGui>
#include "glleak.h"
int main(int argc, char** argv){
QApplication app(argc, argv);
glleak gll(0);
gll.show();
return app.exec();
}
glleak.h
#ifndef GLLEAK_H
#define GLLEAK_H
#include <QGLWidget>
#include <QMouseEvent>
#include <QDebug>
#include <QList>
class glleak : public QGLWidget
{
Q_OBJECT
public:
glleak(QWidget* parent = 0);
virtual ~glleak();
protected:
void initializeGL();
void paintGL();
void resizeGL(int w, int h);
void drawScene(GLenum mode);
void wheelEvent(QWheelEvent* event);
void hardcoreTexturing();
private:
QList<GLuint> texels;
};
#endif // GLLEAK_H
glleak.cpp
glleak::glleak(QWidget* parent) :
QGLWidget(parent)
{
}
glleak::~glleak()
{
}
void glleak::initializeGL(){
glClearColor(0.0f,0.0f,0.0f,0.0f);
glEnable(GL_TEXTURE_2D);
glEnable(GL_MULTISAMPLE);
glLineWidth (1.5f);
glPointSize(4.5f);
glEnable (GL_BLEND);
glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}
void glleak::resizeGL(int w, int h){
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-w/2.0, w/2.0, h/2.0, -h/2.0, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
glViewport(0, 0, w, h);
glLoadIdentity();
}
void glleak::paintGL(){
glPushMatrix();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glColor3f(1.0f,1.0f,1.0f);
drawScene(GL_RENDER);
glPopMatrix();
}
void glleak::drawScene(GLenum mode){
qDebug() << "drawed #" << texels.count() << " Textures";
hardcoreTexturing();
}
void glleak::hardcoreTexturing(){
glEnable(GL_TEXTURE_2D);
for ( int i(0); i<texels.count(); ++i){
glPushMatrix();
glTranslatef(1.1f*i, 2.2f*i, 0.0f);
glBindTexture(GL_TEXTURE_2D, texels.at(i));
glBegin(GL_QUADS);
{
glTexCoord2i(0,0);
glVertex2i(-128,-128);
glTexCoord2i(0,1);
glVertex2i(-128,128);
glTexCoord2i(1,1);
glVertex2i(128,128);
glTexCoord2i(1,0);
glVertex2i(128,-128);
}
glEnd();
glPopMatrix();
}
glDisable(GL_TEXTURE_2D);
}
void glleak::wheelEvent(QWheelEvent* event){
glEnable(GL_TEXTURE_2D);
int n(50);
if (event->delta()>0){
qDebug() << "gen textures";
for (int i(0); i<n; ++i){
QImage t("./ballmer_peak.png","png");
GLuint tex(0);
glGenTextures(1, &tex);
glBindTexture(GL_TEXTURE_2D, tex);
glTexImage2D( GL_TEXTURE_2D, 0, 3, t.width(), t.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, t.bits() );
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
texels.append(tex);
}
}
else{
qDebug() << "del textures";
for (QList<GLuint>::iterator i(texels.begin()); i!=texels.end();){
glDeleteTextures(1, &(*i));
i = texels.erase(i);
if (--n <= 0)
break;
}
}
glDisable(GL_TEXTURE_2D);
updateGL();
}
ballmer_peak.png
A Image to load and render
Note: Compile demo: Just put it all in a folder, rename your image to ballmer_peak.png, call qmake, make, ./glleak
Note: Demo usage: Use mousewheel to generate or delete 50 Textures at once
If I use glDeleteTextures completly wrong, please tell me how to use it.
I am way out of ideas as my usage complies to the official OpenGL glDeleteTextures usage.
This may or may not be the reason for your leak, but for starters you are using glGenTextures wrongly.
1) You should not put this inside the for loop which initializes the textures. You need to put it before the loop and call it ONCE, with the number of textures required as the first parameter. Say n == 50:
glGenTextures(50, &tex);
2) tex should be a static array of n GLuints and should be persisted (not an auto variable as you have it!) until glDeleteTextures has been called, again, ONCE - not in a loop:
glDeleteTextures(50, &tex);
Think of tex as a repository for storing texture ids. It is important you use it and not say a separate QList, as you have done, for binding textures, since (as specified in the OpenGL reference) there is no guarantee that the texture ids will be a contiguous set of integers. I should imagine your leak happens because internally OpenGL loses the original pointer to the local (auto) variable you used to generate each texture, so the texture memory becomes orphaned.
Hope this helps!
I did not run your example code, but I get a similar thing on Windows7-64bits. Using per-texture glGenTextures() and glDeleteTextures(), it might leak memory, but I'm seeing my thread's handle count increase (in TaskManager for example, but I can also check it from the source).
It seems glDeleteTextures() does not release a handle. Perhaps it'd do it later on, but 24-hour tests indicate it never releases the handle. Seems like a leak inside the driver (nVidia GTX285, driver 270.61).
Eventually indeed the program runs out of memory. I'm beginning to think it's a driver issue...
There's nothing that looks wrong in your code. So... What makes you think you have a memory leak ? What makes you think it's textures specifically that leak ?
It is possible, but highly unlikely, that the OpenGL implementation you use leaks. That would be implementation specific.
Whatever the mechanism you use to look at memory leaks, what happens once you free the OpenGL context ?
You may need to call makeCurrent() at the top of wheelEvent.
For paintEvent, resizeEvent etc, Qt provides an implementation which handles this before calling paintGL/resizeGL/etc, but for other events like wheelEvent you have to do it yourself.
I might be doing this wrong, but when I compiled and ran your code I didn't run into any problems? Going up to 650 textures (can't increase further: get a 'killed' message then) and back my ram usage goes up from 1% to 24% and back to 1%. Going up to about 200 and back down repeatedly also doesn't cause problems: ram usage is still 1% at the end. From what I understand this would've caused massive leaks on your system? Ubuntu 10.10 here (Qt 4.7.0).
Your test on my system eats memory well, and not releases it immediatly when I delete all the textures, but if I wait for some time, memory is returned to system.
It seems that OGL driver uses some lazy memory releasing algorithm.
for (QList<GLuint>::iterator i(texels.begin()); i!=texels.end();)
switch to
for (QList<GLuint>::iterator i(texels.end()); i!=texels.begin();)