【小沐学QT】QT学习之OpenGL开发笔记

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。
在这里插入图片描述

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 <QApplication>

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 <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLShaderProgram>

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() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
        return;
    }

    success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/new/prefix1/triangle.frag");
    if (!success) {
        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
        return;
    }

    success = shaderProgram.link();
    if(!success) {
        qDebug() << "shaderProgram link failed!" << shaderProgram.log();
    }

    //VAO，VBO数据部分
    float vertices[] = {
        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();
}

triangle.vert

#version 330 core
layout(location = 0) in vec3 aPos;

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

triangle.frag

#version 330 core
out vec4 FragColor;

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

运行如下：
在这里插入图片描述

3、Qt + QOpenGLWidget + qt函数

qtfunctionwidget.h

#ifndef QTFUNCTIONWIDGET_H
#define QTFUNCTIONWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLShader>
#include <QOpenGLShaderProgram>
#include <QDebug>
#include <QOpenGLFunctions>
#include <QOpenGLVertexArrayObject>
#include <QOpenGLBuffer>

class QtFunctionWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
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.cpp

#include "QtFunctionWidget.h"
#include <QFile>

QtFunctionWidget::QtFunctionWidget(QWidget *parent) : QOpenGLWidget (parent),
    vbo(QOpenGLBuffer::VertexBuffer),
    ebo(QOpenGLBuffer::IndexBuffer)
{

}

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() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
        return;
    }

    success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/new/prefix1/triangle.frag");
    if (!success) {
        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
        return;
    }

    success = shaderProgram.link();
    if(!success) {
        qDebug() << "shaderProgram link failed!" << shaderProgram.log();
    }

    //VAO，VBO数据部分
    GLfloat vertices[] = {
        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();
}

在这里插入图片描述

4、Qt + QOpenGLWindow

untitled4.pro

QT       += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = OpenGL
TEMPLATE = app
CONFIG += c++11

SOURCES += \
    main.cpp \
    mywindow.cpp

HEADERS += \
    mywindow.h

LIBS += -lopengl32\
        -lglu32

main.cpp

#include <QApplication>
#include <MyWindow.h>

int main(int argc, char *argv[])
{
    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();
}

mywindow.h

#ifndef WINDOW_H
#define WINDOW_H

#include <QOpenGLWindow>
#include <QOpenGLFunctions>
#include <QTimer>

class MyWindow : public QOpenGLWindow, protected QOpenGLFunctions
{
    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

mywindow.cpp

#include "mywindow.h"

MyWindow::MyWindow()
{
    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;
}

程序运行如下：
在这里插入图片描述

5、Qt + glut

https://freeglut.sourceforge.net/

freeglut是OpenGL实用工具工具包（GLUT）库的免费软件/开源替代品。GLUT最初由Mark Kilgard编写，用于支持OpenGL“红皮书”第二版中的示例程序。从那时起，GLUT就被广泛应用于各种实际应用中，因为它简单、可用性广、便携性强。
GLUT（以及freeglut）负责创建窗口、初始化OpenGL上下文和处理输入事件所需的所有特定于系统的家务，以实现真正可移植的OpenGL程序。
freeglut是在X-Consortium许可下发布的。

在这里插入图片描述

untitled4.pro

LIBS += -L$$PWD\lib -lfreeglut
CONFIG += c++11
DEFINES += QT_DEPRECATED_WARNINGS
INCLUDEPATH += include

SOURCES += \
    main.cpp

main.cpp

#include "GL/glut.h"

void display(void)
{
    // 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;
}

在这里插入图片描述

程序运行后：

6、Qt + glfw

https://www.glfw.org/

GLFW是一个开源、多平台的库，用于OpenGL、OpenGL ES和Vulkan在桌面上的开发。它提供了一个简单的API，用于创建窗口、上下文和表面，接收输入和事件。
GLFW是用C语言编写的，支持Windows、macOS、Wayland和X11。
GLFW是根据zlib/libpng许可证获得许可的。

在这里插入图片描述

untitled4.pro

LIBS += -L$$PWD\lib -lglfw3 -lopengl32 -lGlU32 -luser32 -lkernel32 -lgdi32

CONFIG += c++11
DEFINES += QT_DEPRECATED_WARNINGS
INCLUDEPATH += include

SOURCES += \
    main.cpp

main.cpp

#include <iostream>
#include "GLFW/glfw3.h"
using namespace std;

int main(int argc, char *argv[])
{
    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;
}

在这里插入图片描述
程序运行如下：

结语

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