OpenGL入门到入坟：Hello Triangle 绘制三角形

操作系统：Win10

工具：VS2019

环境：glfw 3.3.0.1、glew1.9.0.1

测试结果

测试代码

#include <iostream>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
using namespace std;
//窗口背景色
float red, green, blue = 0.0f;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);、
//窗口消息处理函数
void processInput(GLFWwindow* window);

//GLSL编译
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";
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";

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_R) == GLFW_PRESS)
	{
		cout << "当前窗口颜色：Red" << endl;
		green = 0.0f;
		blue = 0.0f;
		red = 1.0f;

	}
	if (glfwGetKey(window, GLFW_KEY_G) == GLFW_PRESS)
	{
		cout << "当前窗口颜色：Green" << endl;
		green = 1.0f;
		blue = 0.0f;
		red = 0.0f;
	}
	if (glfwGetKey(window, GLFW_KEY_B) == GLFW_PRESS)
	{
		cout << "当前窗口颜色：Blue" << endl;
		green = 0.0f;
		blue = 1.0f;
		red = 0.0f;
	}
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		cout << "Window was closed..." << endl;
		glfwSetWindowShouldClose(window, true);
	}
}
//窗口大小视口变换，没搞清楚是怎么用的
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, width, height);
}
int main(int argc, char* argv[])
{
	//初始化glfw，使用3.3版本
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	//开窗600*800,标题OpenGL

	GLFWwindow* window = glfwCreateWindow(600, 800, "OpenGL", NULL, NULL);
	//开窗失败
	if (window == NULL)
	{
		cout << "Creating window fail" << endl;
		glfwTerminate();
		return EXIT_FAILURE;
	}
	//OpenGL是一个状态机，设置这个窗口为当前运行上下文
	glfwMakeContextCurrent(window);

	//glew初始化失败
	glewExperimental = true;
	if (glewInit() != GLEW_OK)
	{
		cout << "glew init fail" << endl;
		glfwTerminate();
		return EXIT_FAILURE;
	}
	glViewport(0, 0, 600, 800);
	//窗口处理函数

	// 创建顶点着色器，源代码为vertexShaderSource字符串，编译
	int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	
	//编译出错显示
	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\n" << infoLog << std::endl;
	}
	// 创建片段着色器，源代码为fragmentShaderSource字符串，编译
	int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	// 编译出错显示
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// 创建程序，链接
	int shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	// 链接程序错误显示
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	//程序已经生成，不需要它们了删除
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	//三角形是顺时针画的
	float vertices[] = {
		 0.5f,  0.5f, 0.0f,  // 三角形上顶点坐标
		 0.5f, -0.5f, 0.0f,  // 三角形右下顶点坐标
		-0.5f, -0.5f, 0.0f,  // 三角形左下顶点坐标
	};
	//VBO：顶点缓冲对象 VAO：顶点数组对象
	unsigned int VBO, VAO;
	//各生成一个对象
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	//OpenGL是状态机，必须要告诉它我们要用哪个顶点数组对象
	glBindVertexArray(VAO);
	//OpenGL是状态机，必须要告诉它我们要用哪个顶点缓冲对象
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	//设置VBO的数据为vertices（三角形三个顶点）这个数组，GL_STATIC_DRAW：不能改变数据
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	//设置属性指针，从偏移地址0（(void*)0）开始取，每次3个GL_FLOAT大小，取完后，地址
	//后移3 * sizeof(float)大小
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);


	while (!glfwWindowShouldClose(window))
	{
		
		processInput(window);

		glClearColor(red, green, blue, 0.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		//使用刚才编译的shaderProgram，其实这一句可以放在循环外（我猜的）
		glUseProgram(shaderProgram);
		//这一句上面已经有了加不加都无所谓，这里循环绑定意义不大（我猜的）
		glBindVertexArray(VAO); 
		//告诉OpenGL我要用顶点数组第0个开始用，用3个画一个三角形
		glDrawArrays(GL_TRIANGLES, 0,3);

		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glfwTerminate();
	return EXIT_SUCCESS;
}