Qt使用OpenGL实现绘制3D图形

QT += widgets

HEADERS += \
    myopenglwidget.h

SOURCES += \
    main.cpp \
    myopenglwidget.cpp

#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QOpenGLBuffer>
#include <QOpenGLTexture>
#include <QOpenGLShaderProgram>
#include <QKeyEvent>

class QOpenGLTexture;
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);

    void keyPressEvent(QKeyEvent *event);

private:
    QOpenGLShaderProgram *program;
    QOpenGLBuffer vbo;
    QOpenGLTexture *textures[2];
    GLfloat translate,xRot,yRot,zRot;
};

#endif // MYOPENGLWIDGET_H

#include "myopenglwidget.h"

MyOpenGLWidget::MyOpenGLWidget(QWidget *parent)
    : QOpenGLWidget(parent)
{
    //初始化变量
    translate = -6.0;
    xRot = zRot = 0.0;
    yRot = -30.0;
}

void MyOpenGLWidget::initializeGL()
{
    //初始化纹理变量
    for(int i=0;i<2;i++)
    {
          textures[i] = new QOpenGLTexture(QImage(QString("../MyOpenGL/side%1.jpg").arg(i+1)).mirrored());
    }

    //为当前环境初始化OpenGL环境
    initializeOpenGLFunctions();

    //开启深度测试
    glEnable(GL_DEPTH_TEST);

    //下列着色器使用书中代码运行报错,进行了修正
    //创建顶点着色器
    QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex,this);
    const char *vsrc = "#version 330\n"
                       "in vec4 vPosition;\n"
                       "in vec2 vTexCoord;\n"
                       "out vec2 texCoord;\n"
                       "uniform mat4 matrix;\n"
                       "void main()\n"
                       "{\n"
                       "    texCoord = vTexCoord;\n"
                       "    gl_Position = matrix * vPosition;\n"
                       "}\n";
    vshader->compileSourceCode(vsrc);

    //创建片段着色器
    QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment,this);
    const char *fsrc = "#version 330\n"
                       "uniform sampler2D tex;\n"
                       "in vec2 texCoord;\n"
                       "out vec4 fColor;\n"
                       "void main()\n"
                       "{\n"
                       "    fColor = texture(tex,texCoord);\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::paintGL()
{
    //设置视口为正方形
    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[2][4][3] =
    {
        {{-0.8f,0.8f,0.8f},{-0.8f,-0.8f,0.8f},{0.8f,-0.8f,0.8f},{0.8f,0.8f,0.8f}},
        {{0.8f,0.8f,0.8f},{0.8f,-0.8f,0.8f},{0.8f,-0.8f,-0.8f},{0.8f,0.8f,-0.8f}}
    };

    //添加缓存
    vbo.create();
    vbo.bind();
    vbo.allocate(vertices,48*sizeof(GLfloat));
    GLuint vPosition = program->attributeLocation("vPosition");
    //glVertexAttribPointer(vPosition,2,GL_FLOAT,GL_FALSE,0,vertices);
    program->setAttributeBuffer(vPosition,GL_FLOAT,0,3,0);
    glEnableVertexAttribArray(vPosition);

    //顶点着色
    GLfloat coords[2][4][2] =
    {
        {{0.0f,1.0f},{0.0f,0.0f},{1.0f,0.0f},{1.0f,1.0f}},
        {{0.0f,1.0f},{0.0f,0.0f},{1.0f,0.0f},{1.0f,1.0f}}
    };
    vbo.write(24*sizeof(GLfloat),coords,16*sizeof(GLfloat));
    GLuint vTexCoord = program->attributeLocation("vTexCoord");
    program->setAttributeBuffer(vTexCoord,GL_FLOAT,24*sizeof(GLfloat),2,0);
    glEnableVertexAttribArray(vTexCoord);
    program->setUniformValue("tex",0);

    //顶点变换
    QMatrix4x4 matrix;
    matrix.perspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f);
    matrix.translate(0,0,translate);
    matrix.rotate(xRot,1.0,0.0,0.0);
    matrix.rotate(yRot,0.0,1.0,0.0);
    matrix.rotate(zRot,0.0,0.0,1.0);
    program->setUniformValue("matrix",matrix);

    //绘制函数
    for(int i=0;i<2;i++)
    {
        textures[i]->bind();
        glDrawArrays(GL_TRIANGLE_FAN,i*4,4);
    }
}

void MyOpenGLWidget::resizeGL(int,int)
{

}

//按键事件
void MyOpenGLWidget::keyPressEvent(QKeyEvent *event)
{
    switch(event->key())
    {
    case Qt::Key_Up:
        xRot -= 10;
        break;
    case Qt::Key_Down:
        xRot += 10;
        break;
    case Qt::Key_Left:
        yRot -= 10;
        break;
    case Qt::Key_Right:
        yRot += 10;
        break;
    case Qt::Key_PageUp:
        zRot -= 10;
        break;
    case Qt::Key_PageDown:
        zRot += 10;
        break;
    case Qt::Key_Space:
        translate += 1;
        break;
    case Qt::Key_Alt:
        translate -= 1;
        break;
    default:
        break;
    }
    update();
    QOpenGLWidget::keyPressEvent(event);
}

#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();
}