Qt OpenGL更新速度太慢

我似乎无法让Qt5以有意义的速度更新我的场景。我的场景是一个512x512纹理的矩形。我得到的速率大约是每秒1帧（！）。

在我的构造函数中

   aTimer.setSingleShot(false);
   aTimer->setTimerType(Qt::PreciseTimer);
   connect(&aTimer,SIGNAL(timeout()),this,SLOT(animate()));
   aTimer.start(50);
   setAutoFillBackground(false);

和

void GLWidget::animate()
{
//Logic for every time step
updateGL();
}

有没有办法设定优先级？我是不是做错了什么？Qt中是否存在某种内在的更新限制，并且肯定不在1 FPS的数量级上？我的理论是，Qt忽略了我实际更新屏幕的调用。

我试过

1. 插入QCoreApplication::processEvents(); ，但这没有帮助
2. 在父窗口小部件上调用update，并从父窗口运行计时器
3. 创建一个名为animate（）的函数，该函数运行forever{}并从中调用update
4. wigglywidget示例似乎有效，这向我暗示QT OpenGL正在以某种方式折叠帧，忽略了我的更新调用。有没有一种启发式方法可以控制这一点

重建的最小代码

（这个版本有点不同，是根据wigglywidget类建模的，但有完全相同的问题）

git clone https://bitbucket.org/FunFarm/qtcapturesoftware.git

glwidget.h

/****************************************************************************/
#ifndef GLWIDGET_H
#define GLWIDGET_H
#include <QGLWidget>
#include <QtOpenGL/qglshaderprogram.h>
#include <QTimer>
#include <math.h>
#include "time.h"
#include <assert.h>
#include <random>
class GLWidget : public QGLWidget
{
    Q_OBJECT
public:
    GLWidget(QWidget *parent = 0);
    ~GLWidget();
    void addNoise();
protected:
    void initializeGL();
    void paintGL();
    void timerEvent(QTimerEvent *event);
    void resizeGL(int width, int height);
private:
    QBasicTimer timer;
    QPoint lastPos;
    GLuint textures[6];
    QVector<QVector2D> vertices;
    QVector<QVector2D> texCoords;
    QGLShaderProgram program1;
    int vertexAttr1;
    int vertexTexr1;
    //
    int heightGL;
    int widthGL;
    //
    GLubyte* noise;
    //
    QTimer* aTimer;
    //
};
#endif

glwidget.cpp

#include <QtWidgets>
#include <QtOpenGL>
#include "glwidget.h"

#ifndef GL_MULTISAMPLE
#define GL_MULTISAMPLE  0x809D
#endif
GLWidget::GLWidget(QWidget *parent)
    : QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
{
    setAutoFillBackground(false);
    aTimer = new QTimer();
    timer.start(30, this); // 30 fps?
}
void GLWidget::timerEvent(QTimerEvent *event)
{
    addNoise();
    update();// Doesn't matter which update function I call, this is the one from the wigglywidget example
}
 GLWidget::~GLWidget(){}
void GLWidget::initializeGL()
{
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glShadeModel(GL_SMOOTH);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_MULTISAMPLE);
    static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
    QGLShader *vshader1 = new QGLShader(QGLShader::Vertex, this);
    const char *vsrc1 =
            "attribute vec2 coord2d;   n"
            "attribute mediump vec4 texCoord;n"
            "varying mediump vec4 texc;n"
            "void main()                  n"
            "{                            n"
            "   gl_Position = vec4(coord2d, 0.0, 1.0); n"
            "   texc = texCoord;n"
            "}                          n";
    vshader1->compileSourceCode(vsrc1);
    QGLShader *fshader1 = new QGLShader(QGLShader::Fragment, this);
    const char *fsrc1 =
            "uniform sampler2D texture;n"
            "varying mediump vec4 texc;n"
            "void main(void)n"
            "{n"
            "    gl_FragColor = texture2D(texture, texc.st);n"
            "}n"                                                  ;
    fshader1->compileSourceCode(fsrc1);
    program1.addShader(vshader1);
    program1.addShader(fshader1);
    program1.link();
    vertexAttr1 = program1.attributeLocation( "coord2d");
    vertexTexr1 = program1.attributeLocation( "texCoord");
    // Create the vertex buffer.
    vertices.clear();
    float u=1;
#define AVEC -u,u
#define BVEC -u,-u
#define CVEC u,u
#define DVEC u,-u
    vertices << QVector2D(AVEC);
    vertices << QVector2D(BVEC);
    vertices << QVector2D(CVEC);
    vertices << QVector2D(BVEC);
    vertices << QVector2D(DVEC);
    vertices << QVector2D(CVEC);
    // Create the texture vertex buffer
#define TAVEC 0,1
#define TBVEC 0,0
#define TCVEC 1,1
#define TDVEC 1,0
    texCoords << QVector2D(TAVEC);
    texCoords << QVector2D(TBVEC);
    texCoords << QVector2D(TCVEC);
    texCoords << QVector2D(TBVEC);
    texCoords << QVector2D(TDVEC);
    texCoords << QVector2D(TCVEC);
    QPixmap aMap(":/images/testmap.jpg");
    assert(aMap.width());
    heightGL = aMap.height();
    widthGL = aMap.width();
    textures[0] =bindTexture(aMap,GL_TEXTURE_2D,GL_LUMINANCE);
    noise = (GLubyte*) calloc(1*widthGL*heightGL,sizeof(GLubyte));//GL_RGB8
    memset(noise,100,1*widthGL*heightGL);
    //
}
void GLWidget::addNoise()
{
    std::default_random_engine e((unsigned int)(time(0)));
    GLubyte c = e()%256;
    assert(noise);
    for (int i = 0; i<heightGL;i++)
    {
        for(int j =0;j<widthGL;j++)
            noise[i*widthGL+j]= c;
    }
}
void GLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    //
    //
    program1.bind();
    program1.setUniformValue("texture", 0);
    program1.enableAttributeArray(vertexAttr1);
    program1.enableAttributeArray(vertexTexr1);
    program1.setAttributeArray(vertexAttr1, vertices.constData());
    program1.setAttributeArray(vertexTexr1, texCoords.constData());
    glBindTexture(GL_TEXTURE_2D, textures[0]);
    glTexSubImage2D(GL_TEXTURE_2D,0,0,0,
                    widthGL,heightGL,GL_LUMINANCE,GL_UNSIGNED_BYTE, //lets hope these are correct
                    noise);
    glDrawArrays(GL_TRIANGLES, 0, vertices.size());
    program1.disableAttributeArray(vertexTexr1);
    program1.disableAttributeArray(vertexAttr1);
    program1.release();
}
void GLWidget::resizeGL(int width, int height)
{
    int side = qMin(width, height);
    glViewport((width - side) / 2, (height - side) / 2, side, side);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-0.5, +0.5, -0.5, +0.5, 4.0, 15.0);
    glMatrixMode(GL_MODELVIEW);
}

main.cpp

/****************************************************************************/
#include <QApplication>
#include <QDesktopWidget>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    //cameraView cV;
    //cV.show();
    GLWidget mW;
    mW.show();
    return a.exec();
}

test.pro

HEADERS       = glwidget.h 
    cameraview.h
SOURCES       = glwidget.cpp 
                main.cpp 
    cameraview.cpp
QT           += opengl widgets
CONFIG += console
CONFIG += c++11
# install
target.path = $$[QT_INSTALL_EXAMPLES]/qt_OpenGL_3x/02_First_Triangle
sources.files = $$SOURCES $$HEADERS $$RESOURCES $$FORMS 02-first-triangle.pro
sources.path = $$[QT_INSTALL_EXAMPLES]/qt_OpenGL_3x/02_First_Triangle
INSTALLS += target sources

simulator: warning(This example might not fully work on Simulator platform)
FORMS += 
    cameraview.ui
RESOURCES += 
    images.qrc
OTHER_FILES +=