QT中学习Opengl---（QOpenGLShaderProgram简化的使用）
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/本章是简化使用shader的使用，让代码更加简单。
最初着色器写法
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader,1,&vertexShaderSource,(nullptr));
glCompileShader(vertexShader);
int success;
char infoLog[512];
glGetShaderiv(vertexShader,GL_COMPILE_STATUS,&success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
//创建片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr);
glCompileShader(fragmentShader);
// check for shader compile errors
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram,vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);这里使用了创建与链接。
LearnOpenGL 处理
书中的做法是自己封装了一个类。
这个类如下：
#ifndef SHADER_H
#define SHADER_H
#include
#include
#include
#include
#include
class Shader
{
public:
unsigned int ID;
// constructor generates the shader on the fly
// ------------------------------------------------------------------------
Shader(const char* vertexPath, const char* fragmentPath)
{
// 1. retrieve the vertex/fragment source code from filePath
std::string vertexCode;
std::string fragmentCode;
std::ifstream vShaderFile;
std::ifstream fShaderFile;
// ensure ifstream objects can throw exceptions:
vShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
fShaderFile.exceptions (std::ifstream::failbit | std::ifstream::badbit);
try
{
// open files
vShaderFile.open(vertexPath);
fShaderFile.open(fragmentPath);
std::stringstream vShaderStream, fShaderStream;
// read file's buffer contents into streams
vShaderStream << vShaderFile.rdbuf();
fShaderStream << fShaderFile.rdbuf();
// close file handlers
vShaderFile.close();
fShaderFile.close();
// convert stream into string
vertexCode = vShaderStream.str();
fragmentCode = fShaderStream.str();
}
catch (std::ifstream::failure& e)
{
std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
}
const char* vShaderCode = vertexCode.c_str();
const char * fShaderCode = fragmentCode.c_str();
// 2. compile shaders
unsigned int vertex, fragment;
// vertex shader
vertex = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex, 1, &vShaderCode, NULL);
glCompileShader(vertex);
checkCompileErrors(vertex, "VERTEX");
// fragment Shader
fragment = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment, 1, &fShaderCode, NULL);
glCompileShader(fragment);
checkCompileErrors(fragment, "FRAGMENT");
// shader Program
ID = glCreateProgram();
glAttachShader(ID, vertex);
glAttachShader(ID, fragment);
glLinkProgram(ID);
checkCompileErrors(ID, "PROGRAM");
// delete the shaders as they're linked into our program now and no longer necessary
glDeleteShader(vertex);
glDeleteShader(fragment);
}
// activate the shader
// ------------------------------------------------------------------------
void use()
{
glUseProgram(ID);
}
// utility uniform functions
// ------------------------------------------------------------------------
void setBool(const std::string &name, bool value) const
{
glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value);
}
// ------------------------------------------------------------------------
void setInt(const std::string &name, int value) const
{
glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
}
// ------------------------------------------------------------------------
void setFloat(const std::string &name, float value) const
{
glUniform1f(glGetUniformLocation(ID, name.c_str()), value);
}
private:
// utility function for checking shader compilation/linking errors.
// ------------------------------------------------------------------------
void checkCompileErrors(unsigned int shader, std::string type)
{
int success;
char infoLog[1024];
if (type != "PROGRAM")
{
glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(shader, 1024, NULL, infoLog);
std::cout << "ERROR::SHADER_COMPILATION_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
}
}
else
{
glGetProgramiv(shader, GL_LINK_STATUS, &success);
if (!success)
{
glGetProgramInfoLog(shader, 1024, NULL, infoLog);
std::cout << "ERROR::PROGRAM_LINKING_ERROR of type: " << type << "\n" << infoLog << "\n -- --------------------------------------------------- -- " << std::endl;
}
}
}
};
#endif
使用方式：
Shader ourShader("3.3.shader.vs", "3.3.shader.fs"); 这两个是着色器的文件，就是我们之前写在代码中的字符串部分
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
out vec3 ourColor;
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor;
}#version 330 core
out vec4 FragColor;
in vec3 ourColor;
void main()
{
FragColor = vec4(ourColor, 1.0f);
}在绘制的时候链接：
ourShader.use();
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);Qt中封装方式：
qt中都给你封装了QOpenGLShaderProgram 中了
若你的代码段是：
//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"
"}\n\0";使用方式是：
shaderProgram.addShaderFromSourceCode(QOpenGLShader::Vertex,vertexShaderSource);
shaderProgram.addShaderFromSourceCode(QOpenGLShader::Fragment,fragmentShaderSource);
shaderProgram.link();绑定部分是：
shaderProgram.bind();
这样我们代码量就减少了非常多了。
如果我们也想写成文件形式，这样我们修改着色器的时候，就十分方便了。
我们创建资源文件。
对应的代码就是前面写过。代码在最后。
代码使用为：
shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex,":/shader/shader.vs");
shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment,":/shader/shader.fs");
shaderProgram.link(); 
#ifndef BKQOPENGLW_H
#define BKQOPENGLW_H
#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;
Shape m_Shape;
QOpenGLShaderProgram shaderProgram;
};
#endif // BKQOPENGLW_H
对应cpp
#include "bkqopenglw.h"
#include
const float vertices[] = {
-0.5f, -0.5f, 0.0f, // left
0.5f, -0.5f, 0.0f, // right
0.0f, 0.5f, 0.0f // top
};
//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"
"}\n\0";
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();
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);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), nullptr);
glEnableVertexAttribArray(0);
// 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);
// 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();
//链接着色器
}
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;
default:
break;
}
}
对应shader.vs
#version 330 core
layout (location = 0) in vec3 position;
void main()
{
gl_Position = vec4(position.x, position.y, position.z, 1.0);
}
对应shader.fs
#version 330 core
out vec4 color;
void main()
{
color = vec4(1.0f, 0.5f, 0.2f, 1.0f);//RGBA
}
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