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OpenGL之着色器
什么是着色器
着色器是使用一种叫GLSL的类C语言写成的。GLSL是为图形计算量身定制的,它包含一些针对向量和矩阵操作的有用特性。着色器的开头总是要声明版本,接着是输入和输出变量、uniform和main函数。每个着色器的入口点都是main函数,在这个函数中我们处理所有的输入变量,并将结果输出到输出变量中。
一个典型的着色器有下面的结构:
#version version_number
in type in_variable_name;
in type in_variable_name;
out type out_variable_name;
uniform type uniform_name;
int main()
{
// 处理输入并进行一些图形操作
...
// 输出处理过的结果到输出变量
out_variable_name = weird_stuff_we_processed;
}
当我们特别谈论到顶点着色器的时候,每个输入变量也叫顶点属性(Vertex Attribute)。我们能声明的顶点属性是有上限的,它一般由硬件来决定。OpenGL确保至少有16个包含4分量的顶点属性可用,但是有些硬件或许允许更多的顶点属性,你可以查询GL_MAX_VERTEX_ATTRIBS来获取具体的上限:
int nrAttributes;
glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, &nrAttributes);
std::cout << "Maximum nr of vertex attributes supported: " << nrAttributes << std::endl;
数据类型
GLSL中包含C等其它语言大部分的默认基础数据类型:
int、float、double、uint和bool。
GLSL也有两种容器类型:
向量(Vector)
vecn: the default vector of n floats
bvecn: a vector of n booleans
ivecn: a vector of n integers
uvecn: a vector of n unsigned integers
dvecn: a vector of n double components
矩阵(Matrix)
输入与输出
虽然着色器是各自独立的小程序,但是它们都是一个整体的一部分,出于这样的原因,我们希望每个着色器都有输入和输出,这样才能进行数据交流和传递。GLSL定义了in和out关键字专门来实现这个目的。每个着色器使用这两个关键字设定输入和输出,只要一个输出变量与下一个着色器阶段的输入匹配,它就会传递下去。但在顶点和片段着色器中会有点不同。
顶点着色器应该接收的是一种特殊形式的输入,否则就会效率低下。顶点着色器的输入特殊在,它从顶点数据中直接接收输入。为了定义顶点数据该如何管理,我们使用location这一元数据指定输入变量,这样我们才可以在CPU上配置顶点属性。顶点着色器需要为它的输入提供一个额外的layout标识,这样我们才能把它链接到顶点数据。
另一个例外是片段着色器,它需要一个vec4颜色输出变量,因为片段着色器需要生成一个最终输出的颜色。如果你在片段着色器没有定义输出颜色,OpenGL会把你的物体渲染为黑色(或白色)。
所以,如果我们打算从一个着色器向另一个着色器发送数据,我们必须在发送方着色器中声明一个输出,在接收方着色器中声明一个类似的输入。当类型和名字都一样的时候,OpenGL就会把两个变量链接到一起,它们之间就能发送数据了(这是在链接程序对象时完成的)。
示例代码:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
const char* vertexShaderSource = "#version 330 core
"
"layout (location = 0) in vec3 aPos;
"
"void main()
"
"{
"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
"
"} ";
const char* fragmentShaderSource = "#version 330 core
"
"out vec4 FragColor;
"
"void main()
"
"{
"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
"
"}
";
void processInput(GLFWwindow* window);
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL) {
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//GLFW将窗口的上下文设置为当前线程的上下文
glfwMakeContextCurrent(window);
//GLAD
// glad: 加载所有OpenGL函数指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// 创建和编译着色器程序
//顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// 检查编译错误
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED
" << infoLog << std::endl;
}
// 片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// 检查编译错误
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED
" << infoLog << std::endl;
}
//着色器程序
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
//链接错误检查
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED
" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
//创建VBO和VAO对象,并赋予ID
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
//绑定VBO和VAO对象
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//为当前绑定到target的缓冲区对象创建一个新的数据存储。
//如果data不是NULL,则使用来自此指针的数据初始化数据存储
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//告知Shader如何解析缓冲里的属性值
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
//开启VAO管理的第一个属性值
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// 渲染循环
while (!glfwWindowShouldClose(window)) {
processInput(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f); //状态设置
glClear(GL_COLOR_BUFFER_BIT); //状态使用
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
// glfw: 交换缓冲区和轮询IO事件(按键按下/释放、鼠标移动等)
glfwSwapBuffers(window);
glfwPollEvents();
}
// glfw: 回收前面分配的GLFW先关资源.
glfwTerminate();
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
return 0;
}
void processInput(GLFWwindow* window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
Uniform
Uniform是一种从CPU中的应用向GPU中的着色器发送数据的方式,但uniform和顶点属性有些不同。首先,uniform是全局的(Global)。全局意味着uniform变量必须在每个着色器程序对象中都是独一无二的,而且它可以被着色器程序的任意着色器在任意阶段访问。第二,无论你把uniform值设置成什么,uniform会一直保存它们的数据,直到它们被重置或更新。
我们可以在一个着色器中添加uniform关键字至类型和变量名前来声明一个GLSL的uniform。从此处开始我们就可以在着色器中使用新声明的uniform了。
#version 330 core
out vec4 FragColor;
uniform vec4 ourColor; // 在OpenGL程序代码中设定这个变量
void main()
{
FragColor = ourColor;
}
我们在片段着色器中声明了一个uniform vec4的ourColor,并把片段着色器的输出颜色设置为uniform值的内容。因为uniform是全局变量,我们可以在任何着色器中定义它们,而无需通过顶点着色器作为中介。顶点着色器中不需要这个uniform,所以我们不用在那里定义它。
如果你声明了一个uniform却在GLSL代码中没用过,编译器会静默移除这个变量,导致最后编译出的版本中并不会包含它,这可能导致几个非常麻烦的错误。
这个uniform现在还是空的;我们还没有给它添加任何数据,所以下面我们就做这件事。我们首先需要找到着色器中uniform属性的索引/位置值。当我们得到uniform的索引/位置值后,我们就可以更新它的值了。这次我们不去给像素传递单独一个颜色,而是让它随着时间改变颜色:
float timeValue = glfwGetTime();
float greenValue = (sin(timeValue) / 2.0f) + 0.5f;
int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
glUseProgram(shaderProgram);
glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);
首先我们通过glfwGetTime()获取运行的秒数。然后我们使用sin函数让颜色在0.0到1.0之间改变,最后将结果储存到greenValue里。
接着,我们用glGetUniformLocation查询uniform ourColor的位置值。我们为查询函数提供着色器程序和uniform的名字(这是我们希望获得的位置值的来源)。如果glGetUniformLocation返回-1就代表没有找到这个位置值。最后,我们可以通过glUniform4f函数设置uniform值。注意,查询uniform地址不要求你之前使用过着色器程序,但是更新一个uniform之前你必须先使用程序(调用glUseProgram),因为它是在当前激活的着色器程序中设置uniform的。
三角形渐变色例子
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>
float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
const char* vertexShaderSource = "#version 330 core
"
"layout (location = 0) in vec3 aPos;
"
"void main()
"
"{
"
"gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
"
"} ";
const char* fragmentShaderSource = "#version 330 core
"
"out vec4 FragColor;
"
"uniform vec4 ourColor;
" // 在我们的 OpenGL 代码中设置该变量的值
"void main()
"
"{
"
" FragColor = ourColor;
"
"}
";
void processInput(GLFWwindow* window);
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL) {
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//GLFW将窗口的上下文设置为当前线程的上下文
glfwMakeContextCurrent(window);
//注册回调函数
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
//GLAD
// glad: 加载所有OpenGL函数指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// 创建和编译着色器程序
//顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// 检查编译错误
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED
" << infoLog << std::endl;
}
// 片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// 检查编译错误
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED
" << infoLog << std::endl;
}
//着色器程序
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
//链接错误检查
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED
" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
//创建VBO和VAO对象,并赋予ID
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
//绑定VBO和VAO对象
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//为当前绑定到target的缓冲区对象创建一个新的数据存储。
//如果data不是NULL,则使用来自此指针的数据初始化数据存储
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//告知Shader如何解析缓冲里的属性值
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
//开启VAO管理的第一个属性值
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// 渲染循环
while (!glfwWindowShouldClose(window)) {
processInput(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f); //状态设置
glClear(GL_COLOR_BUFFER_BIT); //状态使用
float timeValue = glfwGetTime();
float greenValue = (sin(timeValue) / 2.0f) + 0.5f;
int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
glUseProgram(shaderProgram);
glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
// glfw: 交换缓冲区和轮询IO事件(按键按下/释放、鼠标移动等)
glfwSwapBuffers(window);
glfwPollEvents();
}
// glfw: 回收前面分配的GLFW先关资源.
glfwTerminate();
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
return 0;
}
void processInput(GLFWwindow* window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
glViewport(0, 0, width, height);
}
下面是利用同一个数组将顶点数据和颜色数据都存储起来的例子:
由于现在有更多的数据要发送到顶点着色器,我们有必要去调整一下顶点着色器,使它能够接收颜色值作为一个顶点属性输入。需要注意的是我们用layout标识符来把aColor属性的位置值设置为1:
#version 330 core
layout (location = 0) in vec3 aPos; // 位置变量的属性位置值为 0
layout (location = 1) in vec3 aColor; // 颜色变量的属性位置值为 1
out vec3 ourColor; // 向片段着色器输出一个颜色
void main()
{
gl_Position = vec4(aPos, 1.0);
ourColor = aColor; // 将ourColor设置为我们从顶点数据那里得到的输入颜色
}
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>
float vertices[] = { // 位置 // 颜色
0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f, // 右下
-0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, // 左下
0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f // 上
};
const char* vertexShaderSource = "#version 330 core
"
"layout (location = 0) in vec3 aPos;
"
"layout (location = 1) in vec3 aColor;
"
"out vec3 ourColor;
"
"void main()
"
"{
"
"gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
"
"ourColor = aColor;
"
"} ";
const char* fragmentShaderSource = "#version 330 core
"
"out vec4 FragColor;
"
"in vec3 ourColor;
" // 在我们的 OpenGL 代码中设置该变量的值
"void main()
"
"{
"
" FragColor = vec4(ourColor,1.0);
"
"}
";
void processInput(GLFWwindow* window);
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL) {
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//GLFW将窗口的上下文设置为当前线程的上下文
glfwMakeContextCurrent(window);
//注册回调函数
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
//GLAD
// glad: 加载所有OpenGL函数指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// 创建和编译着色器程序
//顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// 检查编译错误
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED
" << infoLog << std::endl;
}
// 片段着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// 检查编译错误
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success) {
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED
" << infoLog << std::endl;
}
//着色器程序
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
//链接错误检查
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED
" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
//创建VBO和VAO对象,并赋予ID
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
//绑定VBO和VAO对象
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//为当前绑定到target的缓冲区对象创建一个新的数据存储。
//如果data不是NULL,则使用来自此指针的数据初始化数据存储
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//告知Shader如何解析缓冲里的属性值
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
//开启VAO管理的第一个属性值
glEnableVertexAttribArray(0);
//告知Shader如何解析缓冲里的属性值
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));
//开启VAO管理的第一个属性值
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// 渲染循环
while (!glfwWindowShouldClose(window)) {
processInput(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f); //状态设置
glClear(GL_COLOR_BUFFER_BIT); //状态使用
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
// glfw: 交换缓冲区和轮询IO事件(按键按下/释放、鼠标移动等)
glfwSwapBuffers(window);
glfwPollEvents();
}
// glfw: 回收前面分配的GLFW先关资源.
glfwTerminate();
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
return 0;
}
void processInput(GLFWwindow* window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
glViewport(0, 0, width, height);
}
从文件中读取
#ifndef SHADER_H
#define SHADER_H
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
class Shader
{
public:
unsigned int ID;
// 构造函数动态生成着色器
// ------------------------------------------------------------------------
Shader(const char* vertexPath, const char* fragmentPath, const char* geometryPath = nullptr)
{
// 1.从文件路径中获取顶点/片段源代码
std::string vertexCode;
std::string fragmentCode;
std::string geometryCode;
std::ifstream vShaderFile;
std::ifstream fShaderFile;
std::ifstream gShaderFile;
// 确保ifstream对象可以引发异常:
vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
gShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
try
{
// 打开文件
vShaderFile.open(vertexPath);
fShaderFile.open(fragmentPath);
std::stringstream vShaderStream, fShaderStream;
// 将文件的缓冲区内容读入流
vShaderStream << vShaderFile.rdbuf();
fShaderStream << fShaderFile.rdbuf();
// 关闭文件
vShaderFile.close();
fShaderFile.close();
// 将流转换为字符串
vertexCode = vShaderStream.str();
fragmentCode = fShaderStream.str();
// 如果存在几何体着色器路径,请同时加载几何体着色器
if (geometryPath != nullptr)
{
gShaderFile.open(geometryPath);
std::stringstream gShaderStream;
gShaderStream << gShaderFile.rdbuf();
gShaderFile.close();
geometryCode = gShaderStream.str();
}
}
catch (std::ifstream::failure& e)
{
std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ: " << e.what() << std::endl;
}
const char* vShaderCode = vertexCode.c_str();
const char* fShaderCode = fragmentCode.c_str();
// 2. 编译着色器
unsigned int vertex, fragment;
// 顶点着色器
vertex = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex, 1, &vShaderCode, NULL);
glCompileShader(vertex);
checkCompileErrors(vertex, "VERTEX");
// 片段着色器
fragment = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment, 1, &fShaderCode, NULL);
glCompileShader(fragment);
checkCompileErrors(fragment, "FRAGMENT");
// 如果给定了几何体着色器,请编译几何体着色器
unsigned int geometry;
if (geometryPath != nullptr)
{
const char* gShaderCode = geometryCode.c_str();
geometry = glCreateShader(GL_GEOMETRY_SHADER);
glShaderSource(geometry, 1, &gShaderCode, NULL);
glCompileShader(geometry);
checkCompileErrors(geometry, "GEOMETRY");
}
// 着色器程序
ID = glCreateProgram();
glAttachShader(ID, vertex);
glAttachShader(ID, fragment);
if (geometryPath != nullptr)
glAttachShader(ID, geometry);
glLinkProgram(ID);
checkCompileErrors(ID, "PROGRAM");
// 删除着色器,因为它们现在链接到着色器程序中,不再需要了
glDeleteShader(vertex);
glDeleteShader(fragment);
if (geometryPath != nullptr)
glDeleteShader(geometry);
}
// 选择着色器程序
// ------------------------------------------------------------------------
void use()
{
glUseProgram(ID);
}
// uniform的实用函数
// ------------------------------------------------------------------------
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);
}
// ------------------------------------------------------------------------
void setVec2(const std::string& name, const glm::vec2& value) const
{
glUniform2fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec2(const std::string& name, float x, float y) const
{
glUniform2f(glGetUniformLocation(ID, name.c_str()), x, y);
}
// ------------------------------------------------------------------------
void setVec3(const std::string& name, const glm::vec3& value) const
{
glUniform3fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec3(const std::string& name, float x, float y, float z) const
{
glUniform3f(glGetUniformLocation(ID, name.c_str()), x, y, z);
}
// ------------------------------------------------------------------------
void setVec4(const std::string& name, const glm::vec4& value) const
{
glUniform4fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}
void setVec4(const std::string& name, float x, float y, float z, float w)
{
glUniform4f(glGetUniformLocation(ID, name.c_str()), x, y, z, w);
}
// ------------------------------------------------------------------------
void setMat2(const std::string& name, const glm::mat2& mat) const
{
glUniformMatrix2fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
// ------------------------------------------------------------------------
void setMat3(const std::string& name, const glm::mat3& mat) const
{
glUniformMatrix3fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
// ------------------------------------------------------------------------
void setMat4(const std::string& name, const glm::mat4& mat) const
{
glUniformMatrix4fv(glGetUniformLocation(ID, name.c_str()), 1, GL_FALSE, &mat[0][0]);
}
private:
// 用于检查着色器编译/链接错误的实用函数。
// ------------------------------------------------------------------------
void checkCompileErrors(GLuint shader, std::string type)
{
GLint success;
GLchar 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 << "
" << infoLog << "
-- --------------------------------------------------- -- " << 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 << "
" << infoLog << "
-- --------------------------------------------------- -- " << std::endl;
}
}
}
};
#endif
shader.vs
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aColor;
// out vec3 ourColor;
out vec3 ourPosition;
void main()
{
gl_Position = vec4(aPos, 1.0);
// ourColor = aColor;
ourPosition = aPos;
}
shader.fs
#version 330 core
out vec4 FragColor;
in vec3 ourPosition;
//uniform vec4 ourColor;
void main()
{
FragColor = vec4(ourPosition, 1.0);
}
main.cpp
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>
#include "../shader.h"
float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
void processInput(GLFWwindow* window);
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);
if (window == NULL) {
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//GLFW将窗口的上下文设置为当前线程的上下文
glfwMakeContextCurrent(window);
//注册回调函数
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
//GLAD
// glad: 加载所有OpenGL函数指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
Shader ourShader("shaders/shader.vs", "shaders/shader.fs");
//创建VBO和VAO对象,并赋予ID
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
//绑定VBO和VAO对象
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//为当前绑定到target的缓冲区对象创建一个新的数据存储。
//如果data不是NULL,则使用来自此指针的数据初始化数据存储
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//告知Shader如何解析缓冲里的属性值
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
//开启VAO管理的第一个属性值
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// 渲染循环
while (!glfwWindowShouldClose(window)) {
processInput(window);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f); //状态设置
glClear(GL_COLOR_BUFFER_BIT); //状态使用
//float timeValue = glfwGetTime();
//float greenValue = (sin(timeValue) / 2.0f) + 0.5f;
ourShader.use();
//ourShader.setVec4("ourColor", 0.0f, greenValue, 0.0f, 1.0f);
//ourShader.setFloat("offsetX", 0.5);
glBindVertexArray(VAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
// glfw: 交换缓冲区和轮询IO事件(按键按下/释放、鼠标移动等)
glfwSwapBuffers(window);
glfwPollEvents();
}
// glfw: 回收前面分配的GLFW先关资源.
glfwTerminate();
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(ourShader.ID);
return 0;
}
void processInput(GLFWwindow* window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height) {
glViewport(0, 0, width, height);
}