【小沐学QT】QT学习之OpenGL开发笔记

2024-06-04 9686阅读

文章目录

  • 1、简介
  • 2、Qt + QOpenGLWidget + gl函数
  • 3、Qt + QOpenGLWidget + qt函数
  • 4、Qt + QOpenGLWindow
  • 5、Qt + glut
  • 6、Qt + glfw
  • 结语

    1、简介

    Qt提供了与OpenGL实现集成的支持，使开发人员有机会在更传统的用户界面的同时显示硬件加速的3D图形。

    Qt有两种主要的UI开发方法：QtQuick和QtWidgets。它们的存在是为了支持不同类型的用户界面，并建立在针对每种类型进行了优化的独立图形引擎上。

    【小沐学QT】QT学习之OpenGL开发笔记 第1张

    可以将在OpenGL图形API中编写的代码与Qt中的这两种用户界面类型结合起来。当应用程序有自己的OpenGL相关代码时，或者当它与基于OpenGL的第三方渲染器集成时，这可能很有用。

    Qt OpenGL模块包含方便类，使这种类型的集成更容易、更快。

    QOpenGLWidget提供了三个方便的虚拟函数，您可以在子类中重新实现这些函数来执行典型的OpenGL任务：

    • paintGL（）-渲染OpenGL场景。每当需要更新小部件时调用。
    • resizeGL（）-设置OpenGL视口、投影等。每当小部件被调整大小时（以及当它第一次显示时，因为所有新创建的小部件都会自动获得调整大小事件），都会调用它。
    • initializeGL（）-设置OpenGL资源和状态。在第一次调用resizeGL（）或paintGL（）之前调用一次。

      最简单的QOpenGLWidget子类可能如下所示：

      class MyGLWidget : public QOpenGLWidget
{
public:
    MyGLWidget(QWidget *parent) : QOpenGLWidget(parent) { }
protected:
    void initializeGL() override
    {
        // Set up the rendering context, load shaders and other resources, etc.:
        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
        f->glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
        ...
    }
    void resizeGL(int w, int h) override
    {
        // Update projection matrix and other size related settings:
        m_projection.setToIdentity();
        m_projection.perspective(45.0f, w / float(h), 0.01f, 100.0f);
        ...
    }
    void paintGL() override
    {
        // Draw the scene:
        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
        f->glClear(GL_COLOR_BUFFER_BIT);
        ...
    }
};

      或者，可以通过从QOpenGLFunctions派生来避免每个OpenGL调用的前缀：

      class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
    ...
    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(...);
        ...
    }
    ...
};

      2、Qt + QOpenGLWidget + gl函数

      • untitled4.pro 
        QT       += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
CONFIG += c++11
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \
    main.cpp \
    qopenglwidgettest.cpp
HEADERS += \
    qopenglwidgettest.h
FORMS += \
    qopenglwidgettest.ui
# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target
RESOURCES += \
    res.qrc
        • main.cpp 
          #include "qopenglwidgettest.h"
#include 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QOpenGLWidgetTest w;
    w.show();
    return a.exec();
}
          • qopenglwidgettest.h 
            #ifndef QOPENGLWIDGETTEST_H
#define QOPENGLWIDGETTEST_H
#include 
#include 
#include 
QT_BEGIN_NAMESPACE
namespace Ui { class QOpenGLWidgetTest; }
QT_END_NAMESPACE
class QOpenGLWidgetTest : public QOpenGLWidget
        , protected /*QOpenGLExtraFunctions*/QOpenGLFunctions_3_3_Core
{
    Q_OBJECT
public:
    QOpenGLWidgetTest(QWidget *parent = nullptr);
    ~QOpenGLWidgetTest();
protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();
private:
    Ui::QOpenGLWidgetTest *ui;
    QOpenGLShaderProgram shaderProgram;
};
#endif // QOPENGLWIDGETTEST_H
            • qopenglwidgettest.cpp 
              #include "qopenglwidgettest.h"
#include "ui_qopenglwidgettest.h"
static GLuint VBO, VAO, EBO;
QOpenGLWidgetTest::QOpenGLWidgetTest(QWidget *parent)
    : QOpenGLWidget(parent)
    , ui(new Ui::QOpenGLWidgetTest)
{
    ui->setupUi(this);
}
QOpenGLWidgetTest::~QOpenGLWidgetTest()
{
    delete ui;
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);
}
void QOpenGLWidgetTest::initializeGL(){
    this->initializeOpenGLFunctions();
    bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/new/prefix1/triangle.vert");
    if (!success) {
        qDebug() 
        qDebug() 
        qDebug() 
        0.5f,  0.5f, 0.0f,  // top right
         0.5f, -0.5f, 0.0f,  // bottom right
        -0.5f, -0.5f, 0.0f,  // bottom left
        -0.5f,  0.5f, 0.0f   // top left
    };
    unsigned int indices[] = {  // note that we start from 0!
        0, 1, 3,  // first Triangle
        1, 2, 3   // second Triangle
    };
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);
    // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);  //顶点数据复制到缓冲
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (void*)0);//告诉程序如何解析顶点数据
    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);//取消VBO的绑定, glVertexAttribPointer已经把顶点属性关联到顶点缓冲对象了
//    remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
//    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
//    You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
//    VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
    glBindVertexArray(0);   //取消VAO绑定
}
void QOpenGLWidgetTest::resizeGL(int w, int h){
    glViewport(0, 0, w, h);
}
void QOpenGLWidgetTest::paintGL(){
    glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    shaderProgram.bind();
    
    glBindVertexArray(VAO); 
//    glDrawArrays(GL_TRIANGLES, 0, 6);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
    shaderProgram.release();
}

    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0f);
}

    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
}

public:
    QtFunctionWidget(QWidget *parent = nullptr);
    ~QtFunctionWidget() Q_DECL_OVERRIDE;
protected:
    virtual void initializeGL() Q_DECL_OVERRIDE;
    virtual void resizeGL(int w, int h) Q_DECL_OVERRIDE;
    virtual void paintGL() Q_DECL_OVERRIDE;
private:
    QOpenGLShaderProgram shaderProgram;
    QOpenGLBuffer vbo, ebo;
    QOpenGLVertexArrayObject vao;
};
#endif // QTFUNCTIONWIDGET_H

}
QtFunctionWidget::~QtFunctionWidget(){
    makeCurrent();
    vbo.destroy();
    ebo.destroy();
    vao.destroy();
    doneCurrent();
}
void QtFunctionWidget::initializeGL(){
    this-initializeOpenGLFunctions();
    bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/new/prefix1/triangle.vert");
    if (!success) {
        qDebug() 
        qDebug() 
        qDebug() 
        0.7f,  0.5f, 0.0f,  // top right
         0.5f, -0.6f, 0.0f,  // bottom right
        -0.6f, -0.5f, 0.0f,  // bottom left
        -0.5f,  0.7f, 0.0f   // top left
    };
    unsigned int indices[] = {  // note that we start from 0!
        0, 1, 3,  // first Triangle
        1, 2, 3   // second Triangle
    };
    QOpenGLVertexArrayObject::Binder vaoBind(&vao);
    vbo.create();
    vbo.bind();
    vbo.allocate(vertices, sizeof(vertices));
    ebo.create();
    ebo.bind();
    ebo.allocate(indices, sizeof(indices));
    int attr = -1;
    attr = shaderProgram.attributeLocation("aPos");
    shaderProgram.setAttributeBuffer(attr, GL_FLOAT, 0, 3, sizeof(GLfloat) * 3);
    shaderProgram.enableAttributeArray(attr);
    vbo.release();
//    remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
//    ebo.release();
}
void QtFunctionWidget::resizeGL(int w, int h){
    glViewport(0, 0, w, h);
}
void QtFunctionWidget::paintGL(){
    glClearColor(0.2f, 0.2f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    shaderProgram.bind();
    {
        QOpenGLVertexArrayObject::Binder vaoBind(&vao);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
    }
    shaderProgram.release();
}

    QApplication a(argc, argv);
    MyWindow w;
    w.setWidth(640);
    w.setHeight(480);
    w.setTitle(QString::fromLocal8Bit("爱看书的小沐"));
    w.show();
    return a.exec();
}

    Q_OBJECT
public:
    MyWindow();
    ~MyWindow();
protected:
    void initializeGL();          //初始化设置
    void resizeGL(int w, int h);  //窗口尺寸变化响应函数
    void paintGL();               //重绘响应函数
private:
    GLfloat angle;                //定义旋转角度
    QTimer *timer;                //定义新的定时器
};
#endif // WINDOW_H

    timer = new QTimer();
    angle = 0.0;
    connect(timer, SIGNAL(timeout()), this, SLOT(update()));
    timer-start(100);
}
MyWindow::~MyWindow()
{
}
void MyWindow::initializeGL()
{
    initializeOpenGLFunctions();
    glClearColor(0.0,0.0,0.0,0.0);
    glClearDepth(1.0);
}
void MyWindow::resizeGL(int w, int h)
{
    Q_UNUSED(w);
    Q_UNUSED(h);
}
void MyWindow::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glRotated(angle,0.0,1.0,0.0);
    glBegin(GL_TRIANGLES);
        glColor3f(1.0,0.0,0.0);
        glVertex3f(0.0,0.8,0.0);
        glColor3f(0.0,0.0,1.0);
        glVertex3f(0.5,0.0,0.0);
        glColor3f(0.0,1.0,0.0);
        glVertex3f(-0.5,0.0,0.0);
    glEnd();
    angle+=10.0;
}

    // clear all pixels
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(0.5, 0.1, 1.0);
    glBegin(GL_POLYGON);
    glVertex3f(0.20, 0.20, 0.0);
    glVertex3f(0.80, 0.20, 0.0);
    glVertex3f(0.80, 0.80, 0.0);
    glVertex3f(0.20, 0.80, 0.0);
    glEnd();
    glFlush();
}
void init(void)
{
    // select clearing color: blue
    glClearColor(0.0, 1.0, 0.0, 0.0);
    // initialize viewing values
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}
int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640, 240);
    glutInitWindowPosition(480, 320);
    glutCreateWindow("爱看书的小沐");
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

    GLFWwindow* window;
    /* Initialize the library */
    if (!glfwInit())
        return -1;
    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }
    /* Make the window's context current */
    glfwMakeContextCurrent(window);
    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);
        /* Swap front and back buffers */
        glfwSwapBuffers(window);
        /* Poll for and process events */
        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}

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