Qt使用OpenGL

1. 添加opengl模块

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QT += openglwidgets

2. 创建OpenGL Widget

需要继承QOpenGLWidget和QOpenGLFunctions_4_5_Core类和重写虚函数。

​ virtual void initializeGL();
​ virtual void resizeGL(int w, int h);
​ virtual void paintGL();

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#ifndef TESTOPENGLWIDGET_H
#define TESTOPENGLWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions_4_5_Core>

class TestOpenGLWidget : public QOpenGLWidget, QOpenGLFunctions_4_5_Core
{
    Q_OBJECT
public:
    enum Shape {
        None, Rect, Circle, Triangle
    };
    explicit TestOpenGLWidget(QWidget *parent = nullptr);
    ~TestOpenGLWidget();

protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();

signals:

private:
};

#endif // TESTOPENGLWIDGET_H

3. 实现OpenGL函数

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#include "testopenglwidget.h"

unsigned int VBO, VAO, EBO;
unsigned int shaderProgram;

float vertices[] = {
    -0.5f,  -0.5f,  0.0f,
    0.5f,   -0.5f,  0.0f,
    0.0f,   0.5f,   0.0f,
};

unsigned int indices[] = {
    0, 1, 3,    // first triangle
    1, 2, 3,    // second triangle
};

const char* vertexShaderSource = "#version 450 core\n"
                                 "layout (location = 0) in vec3 aPos;\n"
                                 "void main()\n"
                                 "{\n"
                                 "gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
                                 "}\0";

const char* fragmentShaderSource = "#version 450 core\n"
                                   "out vec4 FragColor;\n"
                                   "void main()\n"
                                   "{\n"
                                   "FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
                                   "}\0";

TestOpenGLWidget::TestOpenGLWidget(QWidget *parent)
    : QOpenGLWidget{parent}
{
    
}

TestOpenGLWidget::~TestOpenGLWidget()
{
    makeCurrent();
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);
    glDeleteVertexArrays(1, &VAO);
    doneCurrent();
}

void TestOpenGLWidget::initializeGL()
{
    // 初始化OpenGL函数
    initializeOpenGLFunctions();

    // 声明的顶点属性的上限
    int nrAttributes;
    glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, &nrAttributes);
    qDebug() << "-------------------:" << nrAttributes;

    // 创建VBO和VAO对象 并赋予ID
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    // 绑定VBO和VAO对象
    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);

    // 为当前绑定到target的缓冲区对象创建一个新的数据存储。
    // 如果data不为NULL 则使用来自此指针的数据初始化数据存储。
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    // 告知显卡如何解析缓冲里的属性值
    // position attribute
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    // 开启VAO管理的第一个属性值
    glEnableVertexAttribArray(0);
    
    // 顶点着色器
    unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    int success;char infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if(!success) {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        qDebug() << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog;
    }

    // 片段着色器
    unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if(!success) {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        qDebug() << "ERROR::SHADER::FRAGEMENT::COMPILATION_FAILED\n" << infoLog;
    }

    shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    glGetShaderiv(shaderProgram, GL_LINK_STATUS, &success);
    if(!success) {
        glGetShaderInfoLog(shaderProgram, 512, NULL, infoLog);
        qDebug() << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog;
    }
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

}

void TestOpenGLWidget::resizeGL(int w, int h)
{
    Q_UNUSED(w);
    Q_UNUSED(h);
}

void TestOpenGLWidget::paintGL()
{
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glUseProgram(shaderProgram);
    glBindVertexArray(VAO);
    glDrawArrays(GL_TRIANGLES, 0, 3);
}