Qt-OpenGL-03 纹理Texture

写在开头：文章是基于纹理 - LearnOpenGL CN 教程的学习记录，强烈建议在网站上先弄清楚原理再看此文章。以Qt-GL窗口代替GLFW的写法，Qt库中一些类代替教程中的类，一起入坑。

效果图：

上图使用了两纹理混合。接下来是一些比较重要的，使用glUniform1i，可以给纹理采样器分配一个位置值，这样的话我们能够在一个片段着色器中设置多个纹理。一个纹理的位置值通常称为一个纹理单元(Texture Unit)。一个纹理的默认纹理单元是0，它是默认的激活纹理单元，所以教程前面部分我们没有分配一个位置值。

纹理单元的主要目的是让我们在着色器中可以使用多于一个的纹理。通过把纹理单元赋值给采样器，我们可以一次绑定多个纹理，只要我们首先激活对应的纹理单元。就像glBindTexture一样，我们可以使用glActiveTexture激活纹理单元，传入我们需要使用的纹理单元：

如果有需要更多的纹理应当这样：

 //激活纹理单元0glActiveTexture(GL_TEXTURE0);m_combine_texture1->bind();//激活纹理单元1glActiveTexture(GL_TEXTURE1);m_combine_texture2->bind();

OpenGL至少保证有16个纹理单元供你使用，也就是说你可以激活从GL_TEXTURE0到GL_TEXTRUE15。它们都是按顺序定义的，所以我们也可以通过GL_TEXTURE0 + 8的方式获得GL_TEXTURE8，这在当我们需要循环一些纹理单元的时候会很有用.

不同于教程的地方：

用QOpenGLTexture代替stb_image.h

stb_image.h的写法：

glGenTextures(1, &texture2);glBindTexture(GL_TEXTURE_2D, texture2);// set the texture wrapping parametersglTexParameteri(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 parametersglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);// load image, create texture and generate mipmapsdata = stbi_load(FileSystem::getPath("resources/textures/awesomeface.png").c_str(), &width, &height, &nrChannels, 0);if (data){// note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBAglTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);glGenerateMipmap(GL_TEXTURE_2D);}else{std::cout << "Failed to load texture" << std::endl;}

QOpenGLTexture的写法：

m_combine_texture2 = new QOpenGLTexture(QImage(":/texture/res/textures/awesomeface.png").mirrored());if(!m_combine_texture2->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture2->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture2->setMagnificationFilter(QOpenGLTexture::Linear);

主要代码：

#ifndef TEXTUREWIDGET_H
#define TEXTUREWIDGET_H#include <QWidget>
#include <QOpenGLWidget>
#include <QOpenGLExtraFunctions>
#include <QDebug>
#include <QOpenGLTexture>
#include "Shader.h"class HelloTexture;
namespace Ui {
class TextureWidget;
class QOpenGLTexture;
}class TextureWidget : public QWidget
{Q_OBJECTpublic:explicit TextureWidget(QWidget *parent = nullptr);~TextureWidget();private:Ui::TextureWidget *ui;HelloTexture *m_contentWidget;
};class HelloTexture : public QOpenGLWidget,protected QOpenGLExtraFunctions
{enum TARGET_STATUS{Original,Combine,Exercise2,Exercise3,Exercise4};public:HelloTexture();~HelloTexture();private:void InitOriginal();void InitCombine();void InitExercise2();void InitExercise3();void InitExercise4();protected:virtual void initializeGL();virtual void resizeGL(int w, int h);virtual void paintGL();
private:TARGET_STATUS m_status;Shader *m_shader;QOpenGLTexture *m_texture;QOpenGLTexture *m_combine_texture1;QOpenGLTexture *m_combine_texture2;
};#endif // TEXTUREWIDGET_H

cpp

#include "texturewidget.h"
#include "ui_texturewidget.h"#include <QImage>TextureWidget::TextureWidget(QWidget *parent) :QWidget(parent),ui(new Ui::TextureWidget)
{ui->setupUi(this);m_contentWidget = new HelloTexture();ui->verticalLayout->addWidget(m_contentWidget);
}TextureWidget::~TextureWidget()
{delete ui;
}static GLuint VBO, VAO, EBO = 0;
HelloTexture::HelloTexture()
{}HelloTexture::~HelloTexture()
{}void HelloTexture::InitOriginal()
{m_status = TARGET_STATUS::Original;m_shader = new Shader(":/shader/res/shaders/getting_started/4.1.texture.vs",":/shader/res/shaders/getting_started/4.1.texture.fs");//垂直镜像mirroredm_texture = new QOpenGLTexture(QImage(":/texture/res/textures/container.jpg").mirrored());if(!m_texture->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_texture->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_texture->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_texture->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_texture->setMagnificationFilter(QOpenGLTexture::Linear);//m_texture->setFormat(QOpenGLTexture::RGBFormat); //将纹理储存为rgb值
}void HelloTexture::InitCombine()
{m_status = TARGET_STATUS::Combine;m_shader = new Shader(":/shader/res/shaders/getting_started/4.2.texture.vs",":/shader/res/shaders/getting_started/4.2.texture.fs");//垂直镜像mirroredm_combine_texture1 = new QOpenGLTexture(QImage(":/texture/res/textures/container.jpg").mirrored());if(!m_combine_texture1->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture1->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture1->setMagnificationFilter(QOpenGLTexture::Linear);m_combine_texture2 = new QOpenGLTexture(QImage(":/texture/res/textures/awesomeface.png").mirrored());if(!m_combine_texture2->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture2->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture2->setMagnificationFilter(QOpenGLTexture::Linear);//设置纹理单元编号m_shader->use();m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture1"), 0);m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture2"), 1);}void HelloTexture::InitExercise2()
{m_status = TARGET_STATUS::Exercise2;m_shader = new Shader(":/shader/res/shaders/getting_started/4.3.texture.vs",":/shader/res/shaders/getting_started/4.3.texture.fs");//垂直镜像mirroredm_combine_texture1 = new QOpenGLTexture(QImage(":/texture/res/textures/container.jpg").mirrored());if(!m_combine_texture1->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::ClampToEdge);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::ClampToEdge);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture1->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture1->setMagnificationFilter(QOpenGLTexture::Linear);m_combine_texture2 = new QOpenGLTexture(QImage(":/texture/res/textures/awesomeface.png").mirrored());if(!m_combine_texture2->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture2->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture2->setMagnificationFilter(QOpenGLTexture::Linear);//设置纹理单元编号m_shader->use();m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture1"), 0);m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture2"), 1);}void HelloTexture::InitExercise3()
{m_status = TARGET_STATUS::Exercise3;m_shader = new Shader(":/shader/res/shaders/getting_started/4.4.texture.vs",":/shader/res/shaders/getting_started/4.4.texture.fs");//垂直镜像mirroredm_combine_texture1 = new QOpenGLTexture(QImage(":/texture/res/textures/container.jpg").mirrored());if(!m_combine_texture1->isCreated()){qDebug() << "Failed to load texture";}m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::ClampToEdge);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::ClampToEdge);m_combine_texture1->setMinificationFilter(QOpenGLTexture::Nearest);m_combine_texture1->setMagnificationFilter(QOpenGLTexture::Nearest);m_combine_texture2 = new QOpenGLTexture(QImage(":/texture/res/textures/awesomeface.png").mirrored());if(!m_combine_texture2->isCreated()){qDebug() << "Failed to load texture";}m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);m_combine_texture2->setMinificationFilter(QOpenGLTexture::Nearest);m_combine_texture2->setMagnificationFilter(QOpenGLTexture::Nearest);//设置纹理单元编号m_shader->use();m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture1"), 0);m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture2"), 1);
}void HelloTexture::InitExercise4()
{m_status = TARGET_STATUS::Exercise4;m_shader = new Shader(":/shader/res/shaders/getting_started/4.5.texture.vs",":/shader/res/shaders/getting_started/4.5.texture.fs");//垂直镜像mirroredm_combine_texture1 = new QOpenGLTexture(QImage(":/texture/res/textures/container.jpg").mirrored());if(!m_combine_texture1->isCreated()){qDebug() << "Failed to load texture";}m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);m_combine_texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);m_combine_texture1->setMinificationFilter(QOpenGLTexture::Linear);m_combine_texture1->setMagnificationFilter(QOpenGLTexture::Linear);m_combine_texture2 = new QOpenGLTexture(QImage(":/texture/res/textures/awesomeface.png").mirrored());if(!m_combine_texture2->isCreated()){qDebug() << "Failed to load texture";}//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);m_combine_texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);m_combine_texture2->setMinificationFilter(QOpenGLTexture::Linear);//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);m_combine_texture2->setMagnificationFilter(QOpenGLTexture::Linear);//设置纹理单元编号m_shader->use();m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture1"), 0);m_shader->m_shaderProgram.setUniformValue(m_shader->m_shaderProgram.uniformLocation("texture2"), 1);//设置混合值m_shader->m_shaderProgram.setUniformValue("mixValue", 0.5f);
}void HelloTexture::initializeGL()
{//初始化functionsthis->initializeOpenGLFunctions();//运行选项//InitOriginal();//InitCombine();//InitExercise2();//InitExercise3();InitExercise4();float ver[32];if(m_status == Exercise2){float vertices[] = {// positions          // colors           // texture coords (note that we changed them to 2.0f!)0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   2.0f, 2.0f, // top right0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   2.0f, 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, 2.0f  // top left};for(int i = 0 ; i < 32; i++){ver[i] = vertices[i];}}else if(m_status == Exercise3){float vertices[] = {// positions          // colors           // texture coords0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   0.55f, 0.55f, // top right0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   0.55f, 0.45f, // bottom right-0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.45f, 0.45f, // bottom left-0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,   0.45f, 0.55f  // top left};for(int i = 0 ; i < 32; i++){ver[i] = vertices[i];}}else{float vertices[] = {// positions          // colors           // texture coords0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f, // top right0.5f, -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};for(int i = 0 ; i < 32; i++){ver[i] = vertices[i];}}unsigned int indices[] = {0, 1, 3, // first triangle1, 2, 3  // second triangle};glGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);glGenBuffers(1, &EBO);glBindVertexArray(VAO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(ver), ver, GL_STATIC_DRAW);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);// position attributeglVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);// color attributeglVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));glEnableVertexAttribArray(1);// texture coord attributeglVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));glEnableVertexAttribArray(2);}void HelloTexture::resizeGL(int w, int h)
{glViewport(0,0,w,h);
}void HelloTexture::paintGL()
{glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);if(m_status == Original){m_texture->bind();}else{//激活纹理单元0glActiveTexture(GL_TEXTURE0);m_combine_texture1->bind();//激活纹理单元1glActiveTexture(GL_TEXTURE1);m_combine_texture2->bind();}// render containerm_shader->use();glBindVertexArray(VAO);glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
}

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