QT中学习Opengl---（纹理加载QOpenGLTexture）

前言：

本文的代码是 LearnOpenGL 中对应代码，这里提供学习，大家喜欢的可去官方网站去看看:

LearnOpenGL-CNhttps://learnopengl-cn.readthedocs.io/zh/latest/ 本章内容为使用qt封装的类来加载纹理以显示。

 gl一般写法：

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture); // all upcoming GL_TEXTURE_2D operations now have effect on this texture object
    // set the texture wrapping parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);	// set texture wrapping to GL_REPEAT (default wrapping method)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    // set texture filtering parameters
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
    int width, height, nrChannels;
    unsigned char *data  = stbi_load("G:/dataQt/OpenglLearn/chap03/triangleTextures/brickwall.jpg",&width,&height,&nrChannels,0);
    //unsigned char *data  = stbi_load("brickwall.jpg",&width,&height,&nrChannels,0);
    if(data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
         qDebug() << "Failed to load texture" ;
    }
    stbi_image_free(data);

QOpenGLTexture 写法：

pTexture = new QOpenGLTexture(QImage(":/images/images/awesomeface.png").mirrored());

然后在绘制前可以绑定一下：

 pTexture->bind(0);
 glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0);

绘制结果如下：

 

全部代码：

#ifndef BKQOPENGLW_H
#define BKQOPENGLW_H

#include 
#include 
#include 
#include 
class BKQOpenglW : public QOpenGLWidget, QOpenGLFunctions_3_3_Core
{
    Q_OBJECT
public:
    enum Shape{None,Rect,circle,Triangle};
    explicit BKQOpenglW(QWidget *parent = nullptr);
    ~BKQOpenglW();
    void drawShapes(Shape shape);
    void setWireFrame(bool b);
protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();

signals:

public slots:

private:
unsigned int VBO, VAO,EBO;
Shape m_Shape;
QOpenGLShaderProgram shaderProgram;
unsigned int texture;
QOpenGLTexture *pTexture;
};

#endif // BKQOPENGLW_H

 对应cpp：

#include "bkqopenglw.h"
#include
#include 

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

float vertices[] = {
        // positions          // colors           // texture coords
         0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f, // top right
         0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f, // bottom right
        -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.0f, 0.0f, // bottom left
        -0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,   0.0f, 1.0f  // top left
    };


unsigned int indices[] = {  // note that we start from 0!
    0, 1, 3,  // first Triangle
    1, 2, 3   // second Triangle
};

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

}

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

void BKQOpenglW::drawShapes(BKQOpenglW::Shape shape)
{
    m_Shape = shape;
    update();
}

void BKQOpenglW::setWireFrame(bool b)
{
    makeCurrent();
    if(b)
    {
       glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    }
    else {
       glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
    }
    update();
    doneCurrent();
}

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

    //    shaderProgram.addShaderFromSourceCode(QOpenGLShader::Vertex,vertexShaderSource);
    //    shaderProgram.addShaderFromSourceCode(QOpenGLShader::Fragment,fragmentShaderSource);
    shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex,":/shader/shader.vs");
    shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment,":/shader/shader.fs");
    shaderProgram.link();
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
    glBindVertexArray(VAO);

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

    //绑定ebo
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices),indices,GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), nullptr);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);
    // texture coord attribute
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);

    //绑定纹理

    pTexture = new QOpenGLTexture(QImage(":/images/images/awesomeface.png").mirrored());
    // note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
    // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
    glBindVertexArray(0);

}

void BKQOpenglW::resizeGL(int w, int h)
{
       glViewport(0,0,w,h);
}

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

    shaderProgram.bind();
    glBindVertexArray(VAO);
    switch (m_Shape) {
    case Triangle:
        glDrawArrays(GL_TRIANGLES,0,3);
        break;
    case Rect:
        pTexture->bind(0);
        glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0);
        break;
    default:
        break;
    }

}

写在后面的话： 

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