计算机图形学（二）——画一个三角形1.0

画一个三角形

不用Shader头文件的版本

#include <iostream>
#define GLEW_STATIC
#include <GL/glew.h>
#include<GLFW/glfw3.h>
const GLint WIDTH = 800, HEIGHT = 600;//新建一个窗口，窗口的宽800， 高600

//顶点着色器，一定有输出，是顶点的坐标信息
//顶点按逆时针顺序来画
const GLchar* vertexShaderSource = "#version 330 core\n"//版本
"layout(location = 0) in vec3 position;\n"  //着色器的位置参数信息。position变量名；vec3(三维向量)类型，向量的每个分量都是浮点型；in表示这个变量要从外界输入。location=0表示进1个参数；location=1表示进两个参数。
"void main()\n"
"{\n"
"gl_Position = vec4(position.x, position.y, position.z, 1.0f);\n"  //gl_Position预保留的变量，包含顶点信息，不需要定义；齐次坐标器（增加一维，达到矩阵移动目的）
"}";

//边缘着色器
const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"//四个参数
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"  //用 = 进行赋值
"}";

int main()
{
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
	glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "Learn OpenGL xxxxxxx", nullptr, nullptr);
	int screenWidth, screenHeight;
	glfwGetFramebufferSize(window, &screenWidth, &screenHeight);

	if (window == nullptr) {
		std::cout << "Failed to create GLFW window" <<
			std::endl;
		glfwTerminate();
		return  -1;
	}

	glfwMakeContextCurrent(window);
	glewExperimental = GL_TRUE;

	if (glewInit() != GLEW_OK) {
		std::cout << "Failed to initialize GLEW" <<
			std::endl;
		glfwTerminate();
		return -1;
	}

	// import and compile the shader
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	GLint success;
	GLchar 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;
	}

	GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);

	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n"
			<< infoLog << std::endl;
	}

	//creat the program and link the program
	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINK_FAILED\n"
			<< infoLog << std::endl;
	}
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	//Triangle
	GLfloat vertices[] =
	{
		-0.5f,-0.5f,0.0f,
		0.5f,-0.5f,0.0f,
		0.0f,0.5f,0.0f
	};

	//VAO将数据和显存中的物理地址相对应，数据放在VBO里，VAO与VBO成对出现
	//一组数据有不同的解读方式，可能有多个VAO，一个VAO一定要对应一个VBO
	GLuint VAO, VBO;
	glGenVertexArrays(1, &VAO);//创建VAO
	glGenBuffers(1, &VBO);

	glBindVertexArray(VAO);//
	glBindBuffer(GL_ARRAY_BUFFER, VBO);

	//把顶点数据传输到显存的物理地址上
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
	// 参数“0”对应VAO的第一行，参数“3”和“ GL_FLOAT”输入三个浮点型，“ GL_FALSE”表示不需要进行标准化
	//“3 * sizeof(GLfloat)”表示步长，“(GLvoid*)0”第一个起始点在哪找
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
	//允许使用
	glEnableVertexAttribArray(0);

	//解绑，与绑定顺序相反
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);


	while (!glfwWindowShouldClose(window)) {
		glViewport(0, 0, screenWidth, screenHeight);
		glfwPollEvents();
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		glUseProgram(shaderProgram);

		glBindVertexArray(VAO);
		glDrawArrays(GL_TRIANGLES, 0, 3);
		glBindVertexArray(0);

		glfwSwapBuffers(window);
	}
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glfwTerminate();
	return 0;
}