Qt+OpenGL-part2

1-2VAO与VBO_哔哩哔哩_bilibili

顶点着色器：

在GPU上创建内存，存储顶点数据

通过顶点缓冲对象（Vertex Buffer Objects,VBO)管理（GL_ARRAY_BUFFER）

在GPU的内存中存储数据，说明这些内存（这些字节）有什么含义。

顶点数组类型（Vertex Array Objects,VAO)

VAO不保存实际数据，而是放置顶点的定义。

position,color

OpenGL 4 Reference Pages (khronos.org)

Reference Guides - The Khronos Group Inc

小结：

关于VAO和VBO

#include "openglwidget.h"
unsigned int VBO,VAO;
OpenGLWidget::OpenGLWidget(QWidget *parent) : QOpenGLWidget(parent)
{

}

void OpenGLWidget::initializeGL()
{
    initializeOpenGLFunctions();

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

    glGenVertexArrays(1,&VAO);
    glGenBuffers(1,&VBO);

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER,VBO);

    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);

    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,3*sizeof(float),(void *)0);

    glBindBuffer(GL_ARRAY_BUFFER,0);
    glBindVertexArray(0);
}

void OpenGLWidget::resizeGL(int w, int h)
{

}

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

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER,VBO);
    glDrawArrays(GL_TRIANGLES,0,3);
}

1-3编译链接着色器_哔哩哔哩_bilibili

经过一些努力，终于可以画出三角形了。。。

#ifndef OPENGLWIDGET_H
#define OPENGLWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>

class OpenGLWidget : public QOpenGLWidget,QOpenGLFunctions_3_3_Core
{
    Q_OBJECT
public:
    explicit OpenGLWidget(QWidget *parent = nullptr);
protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();
signals:

public slots:
};

#endif // OPENGLWIDGET_H

#include "openglwidget.h"
#include <QDebug>

unsigned int VBO,VAO;
unsigned int shaderProgram;

//顶点着色器
const char* vertexShaderSource="#version 330 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";
//片段着色器
const char* fragmentShaderSource="#version 330 core\n"
        "out vec4 FragColor;\n"
        "void main()\n"
        "{\n"
        "FragColor=vec4(1.0f,0.5f,0.2f,1.0f);\n"
        "}\0";

OpenGLWidget::OpenGLWidget(QWidget *parent) : QOpenGLWidget(parent)
{

}

void OpenGLWidget::initializeGL()
{
    initializeOpenGLFunctions();

    //三角形的三个点(x,y,z)
    float vertices[]={
        -0.5f,-0.5f,0.0f,
        0.5f,-0.5f,0.0f,
        0.0f,0.5f,0.0f
    };
    //顶点数组
    glGenVertexArrays(1,&VAO);
    //顶点缓冲对象
    glGenBuffers(1,&VBO);
    
    //绑定顶点数组
    glBindVertexArray(VAO);
    //绑定顶点缓冲对象
    glBindBuffer(GL_ARRAY_BUFFER,VBO);
    
    //把三角形相关数据复制到缓冲内存中
    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);
    //第二个参数：数据的大小（字节为单位）
    //第三个参数：数据指针
    

    glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,3*sizeof(float),(void *)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER,0);
    glBindVertexArray(0);


    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;
    }

    unsigned int fragmentShader=glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL);
    glCompileShader(fragmentShader);

    shaderProgram=glCreateProgram();
    glAttachShader(shaderProgram,vertexShader);
    glAttachShader(shaderProgram,fragmentShader);
    glLinkProgram(shaderProgram);

    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if(!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        qDebug() << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog;
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

}

void OpenGLWidget::resizeGL(int w, int h)
{

}

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

    glUseProgram(shaderProgram);

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

OpenGL入门教程之 深入三角形_opengl绘制三角形平移旋转-CSDN博客