//顶点输入
//顶点着色器
//编译
//片段着色器
//编译
//着色器程序
//链接顶点属性
//顶点数组对象
//绘制图形
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
//函数声明
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// settings
//定义窗口宽度与高度
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
//着色器源码
//版本声明
//使用in关键字,在顶点着色器中声明所有的输入顶点属性(Input Vertex Attribute)
//通过layout (location = 0)设定了输入变量的位置值(Location)
//把位置数据赋值给预定义的gl_Position变量,设置顶点着色器的输出
//vec4(aPos.x, aPos.y, aPos.z, 1.0)转换为vec4类型
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";
//片段着色器源码
//版本声明
//片段着色器只需要一个输出变量,这个变量是一个4分量向量,它表示的是最终的输出颜色
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";
int main()
{
// glfw: initialize and configure
// ------------------------------
glfwInit();//初始化GLFW
// 名称 版本号
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//配置GLFW
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// glfw window creation
// --------------------
//创建窗口
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
//失败处理
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
//注册窗口回调函数
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// glad: load all OpenGL function pointers
// ---------------------------------------
//GLAD管理OpenGL的函数指针
//初始化GLAD
//glfwGetProcAddress 函数指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// build and compile our shader program
// ------------------------------------
// vertex shader-----------------------
//顶点着色器:把3D坐标转为另一种3D坐标,同时顶点着色器允许我们对顶点属性进行一些基本处理。
//引用ID
int vertexShader = glCreateShader(GL_VERTEX_SHADER);
//将着色器源码附加到着色器对象上 ???
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
//编译着色器
glCompileShader(vertexShader);
// check for shader compile errors
//检查是否编译成功
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
//错误信息
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// fragment shader---------------------
//片段着色器:计算像素最后的颜色输出
//引用ID
int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
//将片段着色器源码附加到片段着色器对象上
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
//编译、
glCompileShader(fragmentShader);
// check for shader compile errors
//检查错误
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
//错误信息
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// link shaders------------------------
//着色器程序:着色器程序对象(Shader Program Object)是多个着色器合并之后并最终链接完成的版本
//创建着色器程序对象,ID引用
int shaderProgram = glCreateProgram();
//将之前编译的着色器附加到程序对象上,然后用glLinkProgram链接它们
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// check for linking errors
//同样,检查错误
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
//删除着色器对象
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
//顶点输入
float vertices[] = {
-0.5f, -0.5f, 0.0f, // left
0.5f, -0.5f, 0.0f, // right
0.0f, 0.5f, 0.0f // top
};
//顶点数组对象:Vertex Array Object,VAO
//顶点缓冲对象:Vertex Buffer Object,VBO
//索引缓冲对象:Element Buffer Object,EBO或Index Buffer Object,IBO
unsigned int VBO, VAO;
//生成顶点数组对象名
//任何随后的顶点属性调用都会储存在这个VAO中
glGenVertexArrays(1, &VAO);
//生成VBO对象:管理存储在GPU中的顶点数据;可以一次性发送大批数据到显卡上
glGenBuffers(1, &VBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
//使用glBindVertexArray绑定VAO。从绑定之后起,我们应该绑定和配置对应的VBO和属性指针,之后解绑VAO供之后使用。
//当我们打算绘制一个物体的时候,我们只要在绘制物体前简单地把VAO绑定到希望使用的设定上就行了。
glBindVertexArray(VAO);
//把新创建的缓冲绑定到GL_ARRAY_BUFFER目标上
glBindBuffer(GL_ARRAY_BUFFER, VBO);
//将之前定义的顶点数据复制到顶点缓冲对象中
//第四个参数
//GL_STATIC_DRAW :数据不会或几乎不会改变。
//GL_DYNAMIC_DRAW:数据会被改变很多。
//GL_STREAM_DRAW :数据每次绘制时都会改变。
//后两者适用于数据频繁改变的情形,例如动画?
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//链接顶点属性
//第一个参数指定我们要配置的顶点属性。还记得我们在顶点着色器中使用layout(location = 0)定义了position顶点属性的位置值(Location)吗?它可以把顶点属性的位置值设置为0。因为我们希望把数据传递到这一个顶点属性中,所以这里我们传入0。
//第二个参数指定顶点属性的大小。顶点属性是一个vec3,它由3个值组成,所以大小是3。
//第三个参数指定数据的类型,这里是GL_FLOAT(GLSL中vec*都是由浮点数值组成的)。
//下个参数定义我们是否希望数据被标准化(Normalize)。如果我们设置为GL_TRUE,所有数据都会被映射到0(对于有符号型signed数据是-1)到1之间。我们把它设置为GL_FALSE。
//第五个参数叫做步长(Stride),它告诉我们在连续的顶点属性组之间的间隔。由于下个组位置数据在3个float之后,我们把步长设置为3 * sizeof(float)。
//最后一个参数的类型是void*,所以需要我们进行这个奇怪的强制类型转换。它表示位置数据在缓冲中起始位置的偏移量(Offset)。
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
//使用glEnableVertexAttribArray,以顶点属性位置值作为参数,启用顶点属性;
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);
// uncomment this call to draw in wireframe polygons.
//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
// render loop
// -----------
//循环渲染:主动关闭前不断绘制图像
//glfwWindowShouldClose(window):检查是否要求退出
while (!glfwWindowShouldClose(window))
{
// input
// -----
//调用检测用户输入函数
processInput(window);
// render
// ------
//以一个自定义颜色清空屏幕
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// draw our first triangle
//调用glUseProgram函数,激活程序对象
//激活后,每个着色器调用和渲染调用都会使用这个程序对象
glUseProgram(shaderProgram);
glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
//第一个参数是绘制的OpenGL图元的类型
//第二个参数指定顶点数组的起始索引
//最后一个参数指定绘制的顶点数
glDrawArrays(GL_TRIANGLES, 0, 3);
// glBindVertexArray(0); // no need to unbind it every time
// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
// -------------------------------------------------------------------------------
//双缓冲
glfwSwapBuffers(window);
//事件检测
glfwPollEvents();
}
// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
//清理资源
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
////获取用户输入
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
////回调函数,在窗口大小被调整时调用
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
glViewport(0, 0, width, height);
}
LearnOpenGL代码注释-你好,三角形
猜你喜欢
转载自blog.csdn.net/qq_33446100/article/details/82782617
今日推荐
周排行