QT OPENGL 入门教程基于QOpenGLWidget 使用缓存绘制多边形

QT OPENGL 入门教程基于 QOpenGLWidget 使用缓存绘制多边形

//myopenglwidget.h
#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H
 
#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QOpenGLBuffer>
 
class QOpenGLShaderProgram;
 
class MyOpenGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
    Q_OBJECT
 
public:
    explicit MyOpenGLWidget(QWidget *parent = 0);
 
protected:
    void initializeGL();
    void paintGL();
    void resizeGL(int width, int height);
 
private:
    QOpenGLShaderProgram *program;
    QOpenGLBuffer vbo;
};
 
#endif // MYOPENGLWIDGET_H
 
//myopenglwidget.cpp
#include "myopenglwidget.h"
#include <QOpenGLShaderProgram>
 
MyOpenGLWidget::MyOpenGLWidget(QWidget *parent)
    : QOpenGLWidget(parent)
{
}
 
void MyOpenGLWidget::initializeGL()
{
    // 为当前环境初始化OpenGL函数
    initializeOpenGLFunctions();
 
    // 创建顶点着色器
    QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex, this);
    const char *vsrc =
            "in vec4 vPosition;                        \n"
            "void main() {                             \n"
            "   gl_Position = vPosition;               \n"
            "}                                         \n";
    vshader->compileSourceCode(vsrc);
    // 创建片段着色器
    QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment, this);
    const char *fsrc =
            "void main() {                              \n"
            "   gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);\n"
            "}                                          \n";
    fshader->compileSourceCode(fsrc);
 
    // 创建着色器程序
    program = new QOpenGLShaderProgram;
    program->addShader(vshader);
    program->addShader(fshader);
 
    program->link();
    program->bind();
}
 
void MyOpenGLWidget::resizeGL(int , int )
{  
}
 
void MyOpenGLWidget::paintGL()
{
    int w = width();
    int h = height();
    int side = qMin(w, h);
    glViewport((w - side) / 2, (h - side) / 2, side, side);
 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
    // 顶点位置
    GLfloat vertices[] = {
        -0.8f, 0.8f,
        -0.8f, -0.8f,
        0.8f, -0.8f,
        0.8f, 0.8f
    };
 
    vbo.create();
    vbo.bind();
    vbo.allocate(vertices, 8*sizeof(GLfloat));
 
    GLuint vPosition = program->attributeLocation("vPosition");
    //为着色器中的位置设定顶点缓存
    program->setAttributeBuffer(vPosition, GL_FLOAT, 0, 2, 0);
    //启用定点数组
    glEnableVertexAttribArray(vPosition);
 
    // 绘制
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
}
 
 
 
//main.cpp
#include <QApplication>
#include "myopenglwidget.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc,argv);
    MyOpenGLWidget w;
    w.resize(400, 300);
    w.show();
    return app.exec();
}