基于Qt的OpenGL学习（3）—— 纹理
2019-08-08 本文已影响0人
玖零儛
简介
要学习OpenGL的话，强烈安利这个教程JoeyDeVries的learnopengl，这里是中文翻译好的版本。教程中使用OpenGL是通过GLFW这个库，而在Qt中对OpenGL封装得很好，并且和GUI以及IO相关的处理Qt更便捷，学习起来更轻松。这里就对每篇教程，在Qt在分别直接使用OpenGL的函数和Qt封装好的类以作对比。
教程中使用的OpenGL版本为3.3，在Qt中需要使用此版本的OpenGL只需要继承类QOpenGLFunctions_3_3_Core即可。如果为了在不同设备上都能用OpenGL的话，Qt提供了类QOpenGLFunctions，这个类包含了大部分公共的函数，可能会有个别函数不能用。
对比说明
教程地址
原教程地址，相关知识可以点击链接学习。
我的工程地址，准备后期每篇教程一个commit，可以切换着看，查看本篇代码 git checkout v1.3，喜欢就点个Star吧~
不同点 (仅列出新增)
- Qt提供了
QOpenGLTexture类来处理OpenGL中的Texture，并且创建的时候可以直接传递一个QImage给纹理对象，如果使用gl相关函数还要读取图片数据的data再设置，比较麻烦。
运行结果
运行结果
使用OpenGL函数版
CoreFunctionWidget.h
#ifndef COREFUNCTIONWIDGET_H
#define COREFUNCTIONWIDGET_H
#include <QOpenGLWidget>
#include <QOpenGLExtraFunctions>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLShader>
#include <QOpenGLShaderProgram>
class CoreFunctionWidget : public QOpenGLWidget
, protected /*QOpenGLExtraFunctions*/QOpenGLFunctions_3_3_Core
{
Q_OBJECT
public:
explicit CoreFunctionWidget(QWidget *parent = nullptr);
~CoreFunctionWidget();
protected:
virtual void initializeGL();
virtual void resizeGL(int w, int h);
virtual void paintGL();
private:
QOpenGLShaderProgram shaderProgram;
// QTimer* m_pTimer = nullptr;
// float m_uniformValue = 0.0f;
};
#endif // COREFUNCTIONWIDGET_H
CoreFunctionWidget.cpp
#include "CoreFunctionWidget.h"
#include <QDebug>
#include <QTimer>
static GLuint VBO, VAO, EBO, texture1, texture2;
CoreFunctionWidget::CoreFunctionWidget(QWidget *parent) : QOpenGLWidget(parent)
{
// m_pTimer = new QTimer(this);
// m_pTimer->setInterval(200);
// connect(m_pTimer, &QTimer::timeout, this, [=]{
// m_uniformValue += 0.1f;
// if (m_uniformValue > 1.5f) {
// m_uniformValue = -1.5f;
// }
// update();
// });
// m_pTimer->start();
}
CoreFunctionWidget::~CoreFunctionWidget()
{
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteBuffers(1, &EBO);
}
void CoreFunctionWidget::initializeGL(){
this->initializeOpenGLFunctions();
bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/textures.vert");
if (!success) {
qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
return;
}
success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/textures.frag");
if (!success) {
qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
return;
}
success = shaderProgram.link();
if(!success) {
qDebug() << "shaderProgram link failed!" << shaderProgram.log();
}
//VAO，VBO data
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
};
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glGenBuffers(1, &EBO);
// 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);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
// position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// color attribute
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);
// texture 1
// ---------
glGenTextures(1, &texture1);
glBindTexture(GL_TEXTURE_2D, texture1);
// 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);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// load image, create texture and generate mipmaps
QImage img1 = QImage(":/container.jpg").convertToFormat(QImage::Format_RGB888);
if (!img1.isNull()) {
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img1.width(), img1.height(), 0, GL_RGB, GL_UNSIGNED_BYTE, img1.bits());
glGenerateMipmap(GL_TEXTURE_2D);
}
// texture 2
// ---------
glGenTextures(1, &texture2);
glBindTexture(GL_TEXTURE_2D, texture2);
// 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);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// load image, create texture and generate mipmaps
QImage img2 = QImage(":/awesomeface.png").convertToFormat(QImage::Format_RGBA8888).mirrored(true, true);
if (!img2.isNull()) {
// note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBA
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img2.width(), img2.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img2.bits());
glGenerateMipmap(GL_TEXTURE_2D);
}
// tell opengl for each sampler to which texture unit it belongs to (only has to be done once)
shaderProgram.bind(); // don't forget to activate/use the shader before setting uniforms!
glUniform1i(shaderProgram.uniformLocation("texture1"), 0);
glUniform1i(shaderProgram.uniformLocation("texture2"), 1);
shaderProgram.release();
// glBindBuffer(GL_ARRAY_BUFFER, 0);//取消VBO的绑定
// remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
// glBindBuffer(GL_ELEMENT_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); //取消VAO绑定
//线框模式，QOpenGLExtraFunctions没这函数, 3_3_Core有
// glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
}
void CoreFunctionWidget::resizeGL(int w, int h){
glViewport(0, 0, w, h);
}
void CoreFunctionWidget::paintGL(){
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
shaderProgram.bind();
{
// bind textures on corresponding texture units
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture1);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, texture2);
// render container
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
}
shaderProgram.release();
}
使用Qt相关函数版
QtFunctionWidget.h
#ifndef QTFUNCTIONWIDGET_H
#define QTFUNCTIONWIDGET_H
#include <QOpenGLWidget>
#include <QOpenGLWidget>
#include <QOpenGLShader>
#include <QOpenGLShaderProgram>
#include <QOpenGLFunctions>
#include <QOpenGLVertexArrayObject>
#include <QOpenGLBuffer>
#include <QOpenGLTexture>
class QtFunctionWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
public:
QtFunctionWidget(QWidget *parent = nullptr);
~QtFunctionWidget() Q_DECL_OVERRIDE;
protected:
virtual void initializeGL() Q_DECL_OVERRIDE;
virtual void resizeGL(int w, int h) Q_DECL_OVERRIDE;
virtual void paintGL() Q_DECL_OVERRIDE;
private:
QOpenGLShaderProgram shaderProgram;
QOpenGLBuffer vbo, ebo;
QOpenGLVertexArrayObject vao;
QOpenGLTexture *texture1 = nullptr;
QOpenGLTexture *texture2 = nullptr;
// QTimer* m_pTimer = nullptr;
// float m_uniformValue = 0.0f;
};
#endif // QTFUNCTIONWIDGET_H
QtFunctionWidget.cpp
#include "QtFunctionWidget.h"
#include <QDebug>
#include <QTimer>
QtFunctionWidget::QtFunctionWidget(QWidget *parent) : QOpenGLWidget (parent),
vbo(QOpenGLBuffer::VertexBuffer),
ebo(QOpenGLBuffer::IndexBuffer)
{
// m_pTimer = new QTimer(this);
// m_pTimer->setInterval(200);
// connect(m_pTimer, &QTimer::timeout, this, [=]{
// m_uniformValue += 0.1f;
// if (m_uniformValue > 1.5f) {
// m_uniformValue = -1.5f;
// }
// update();
// });
// m_pTimer->start();
}
QtFunctionWidget::~QtFunctionWidget(){
makeCurrent();
vbo.destroy();
ebo.destroy();
vao.destroy();
delete texture1;
delete texture2;
doneCurrent();
}
void QtFunctionWidget::initializeGL(){
this->initializeOpenGLFunctions();
bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/textures.vert");
if (!success) {
qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
return;
}
success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/textures.frag");
if (!success) {
qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
return;
}
success = shaderProgram.link();
if(!success) {
qDebug() << "shaderProgram link failed!" << shaderProgram.log();
}
//VAO，VBO data
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
};
QOpenGLVertexArrayObject::Binder vaoBind(&vao);
vbo.create();
vbo.bind();
vbo.allocate(vertices, sizeof(vertices));
ebo.create();
ebo.bind();
ebo.allocate(indices, sizeof(indices));
// position attribute
int attr = -1;
attr = shaderProgram.attributeLocation("aPos");
shaderProgram.setAttributeBuffer(attr, GL_FLOAT, 0, 3, sizeof(GLfloat) * 8);
shaderProgram.enableAttributeArray(attr);
// color attribute
attr = shaderProgram.attributeLocation("aColor");
shaderProgram.setAttributeBuffer(attr, GL_FLOAT, sizeof(GLfloat) * 3, 3, sizeof(GLfloat) * 8);
shaderProgram.enableAttributeArray(attr);
// texture coord attribute
attr = shaderProgram.attributeLocation("aTexCoord");
shaderProgram.setAttributeBuffer(attr, GL_FLOAT, sizeof(GLfloat) * 6, 2, sizeof(GLfloat) * 8);
shaderProgram.enableAttributeArray(attr);
// texture 1
// ---------
texture1 = new QOpenGLTexture(QImage(":/container.jpg"), QOpenGLTexture::GenerateMipMaps); //直接生成绑定一个2d纹理, 并生成多级纹理MipMaps
if(!texture1->isCreated()){
qDebug() << "Failed to load texture";
}
// set the texture wrapping parameters
texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);// 等于glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
// set texture filtering parameters
texture1->setMinificationFilter(QOpenGLTexture::Linear); //等价于glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
texture1->setMagnificationFilter(QOpenGLTexture::Linear);
// texture 2
// ---------
texture2 = new QOpenGLTexture(QImage(":/awesomeface.png").mirrored(true, true), QOpenGLTexture::GenerateMipMaps); //直接生成绑定一个2d纹理, 并生成多级纹理MipMaps
if(!texture2->isCreated()){
qDebug() << "Failed to load texture";
}
// set the texture wrapping parameters
texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);// 等于glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
// set texture filtering parameters
texture2->setMinificationFilter(QOpenGLTexture::Linear); //等价于glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
texture1->setMagnificationFilter(QOpenGLTexture::Linear);
// tell opengl for each sampler to which texture unit it belongs to (only has to be done once)
shaderProgram.bind(); // don't forget to activate/use the shader before setting uniforms!
shaderProgram.setUniformValue("texture1", 0);
shaderProgram.setUniformValue("texture2", 1);
shaderProgram.release();
vbo.release();
// remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
// ebo.release();
}
void QtFunctionWidget::resizeGL(int w, int h){
glViewport(0, 0, w, h);
}
void QtFunctionWidget::paintGL(){
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
shaderProgram.bind();
{
glActiveTexture(GL_TEXTURE0);
texture1->bind();
// glBindTexture(GL_TEXTURE_2D, texture1->textureId());
glActiveTexture(GL_TEXTURE1);
texture2->bind();
// glBindTexture(GL_TEXTURE_2D, texture2->textureId());
// render container
QOpenGLVertexArrayObject::Binder vaoBind(&vao);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
texture1->release();
texture2->release();
}
shaderProgram.release();
}
GLSL
textures.vert
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
layout (location = 2) in vec2 aTexCoord;
out vec3 ourColor;
out vec2 TexCoord;
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor;
TexCoord = aTexCoord;
}
textures.frag
#version 330 core
out vec4 FragColor;
in vec3 ourColor;
in vec2 TexCoord;
uniform sampler2D texture1;
uniform sampler2D texture2;
void main()
{
//FragColor = texture(texture1, TexCoord) * vec4(ourColor, 1.0);
FragColor = mix(texture(texture1, TexCoord), texture(texture2, TexCoord), 0.2);
}
main.cpp
#include <QApplication>
#include "MainWindow.h"
#include "QtFunctionWidget.h"
#include "CoreFunctionWidget.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
// MainWindow w;
QtFunctionWidget w1;
CoreFunctionWidget w2;
w1.setWindowTitle(QObject::tr("QtFunction"));
w2.setWindowTitle(QObject::tr("CoreFunction"));
w1.show();
w2.show();
return a.exec();
}
