Qt+OpenGL——索引绘制四边形

小咪咪 2023-03-01 09:40 32阅读 0赞

头文件

#ifndef GLWIDGET_H
    #define GLWIDGET_H
    
    #include <QOpenGLWidget>
    #include <QOpenGLFunctions_4_5_Core>
    
    #include <QOpenGLShaderProgram>
    
    class GLWidget : public QOpenGLWidget,public QOpenGLFunctions_4_5_Core
    {
        
        Q_OBJECT
    public:
        explicit GLWidget(QWidget *parent=nullptr);
        ~GLWidget();
    
    protected:
    
        void iniDatas();
    
        void initializeGL(); //初始化相关的操作全在这个函数中完成
        void resizeGL(int w,int h);
        void paintGL();
    private:
        QOpenGLShaderProgram *m_pShaderProgram = nullptr;
    
    };
    
    #endif // GLWIDGET_H

源文件

#include "glwidget.h"
    #include <QOpenGLBuffer>
    
    #include <QDebug>
    
    
    #define BUFFER_OFFSET(offset) ((void*)(offset))
    
    
    GLuint VAO = -1;
    GLWidget::GLWidget(QWidget *parent):
        QOpenGLWidget(parent)
    {
        
    
    }
    
    GLWidget::~GLWidget()
    {
        
    
    }
    
    void GLWidget::iniDatas()
    {
        
        static const float triangle[]={
        
            -0.5f,-0.5f,0.0f,
            0.5f,-0.5f,0.0f,
            0.0f,0.5f,0.0f
        };
    
        static const float vertices[] = {
        
            0.5f,0.5f,0.0f,
            0.5f,-0.5f,0.0f,
            -0.5f,-0.5f,0.0f,
            -0.5f,0.5f,0.0f
        };
    
        unsigned int indices[] = {
        
            0,1,2,
            2,0,3
        };
    
        glGenVertexArrays(1,&VAO);
        glBindVertexArray(VAO);
    
        GLuint VBO;
        glGenBuffers(1,&VBO);
        glBindBuffer(GL_ARRAY_BUFFER,VBO);
        glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);
        glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,sizeof(float) * 3,BUFFER_OFFSET(0));
        glEnableVertexAttribArray(0);
    
        GLuint EBO;
        glGenBuffers(1,&EBO);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices),indices,GL_STATIC_DRAW);
    
        glBindVertexArray(0);//解绑
        glBindBuffer(GL_ARRAY_BUFFER,0);
    
        //    glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);//填充图,，默认
        //    glPolygonMode(GL_FRONT_AND_BACK,GL_POINT);//散点图
        glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);//线框图
    }
    
    void GLWidget::initializeGL()
    {
        
        initializeOpenGLFunctions();
    
        m_pShaderProgram = new QOpenGLShaderProgram(this);
        m_pShaderProgram->addShaderFromSourceFile(QOpenGLShader::Vertex,":/shaders/vertext.vert");
        m_pShaderProgram->addShaderFromSourceFile(QOpenGLShader::Fragment,":/shaders/fragment.frag");
        m_pShaderProgram->link();
        m_pShaderProgram->bind();
    
        iniDatas();
    }
    
    void GLWidget::resizeGL(int w, int h)
    {
        
        glViewport(0,0,w,h);
    }
    
    void GLWidget::paintGL()
    {
        
        static const GLfloat color[] = {
        0.0f,0.0f,0.0f,1.0f};
    
        glClearBufferfv(GL_COLOR,0,color);
    
        if(VAO == -1){
        
            return;
        }
    
        glUseProgram(m_pShaderProgram->programId());
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0);
        glBindVertexArray(0);
    
        update();
    }

着色器相关代码

1、顶点着色器

#version 450 core
    
    layout(location=0) in vec3 aPos;
    void main()
    {
        
            gl_Position = vec4(aPos,1);
    }

2、片元着色器

#version 450 core
    out vec4 FragColor;
    
    void main()
    {
        
    	FragColor = vec4(1.0f,0.5f,0.2f,1.0f);
    }

对应效果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0p1aWN5QWN0aXZlR2lsYmVydA_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0p1aWN5QWN0aXZlR2lsYmVydA_size_16_color_FFFFFF_t_70]: /images/20230209/1f8d326637ec4b118ed30b7360b7a53a.png