渲染一个变色矩形

#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>

using namespace std;

void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
{
	// 当用户按下ESC键,我们设置window窗口的WindowShouldClose属性为true
	// 关闭应用程序
	if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
		glfwSetWindowShouldClose(window, GL_TRUE);
}

const GLchar* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 position;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
"}\n\0";

const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"uniform vec4 outColor;"
"void main()\n"
"{\n"
"color = outColor;\n"
"}\n\0";

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_RESIZABLE, GL_FALSE);

	GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", nullptr, nullptr);
	if (window == nullptr)
	{
		std::cout << "Failed to create GLFW window" << std::endl;
		glfwTerminate();
		return -1;
	}

	glfwSetKeyCallback(window, key_callback);

	glfwMakeContextCurrent(window);

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

	int width, height;
	glfwGetFramebufferSize(window, &width, &height);
	glViewport(0, 0, width, height);

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

	GLuint shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	GLfloat vertices[] = {
		0.5f, 0.5f, 0.0f,
		0.5f, -0.5f, 0.0f,
		-0.5f, -0.5f, 0.0f,
		-0.5f, 0.5f, 0.0f,
	};
	GLuint indices[] = {
		0, 1, 3,
		1, 2, 3,
	};
	GLuint VBO, VAO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);
	glBindVertexArray(VAO);

	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
	glEnableVertexAttribArray(0);
	
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	while (!glfwWindowShouldClose(window))
	{
		glfwPollEvents();
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		glUseProgram(shaderProgram);

		GLfloat timeValue = glfwGetTime();
		GLfloat greenValue = (sin(timeValue) / 2) + 0.5;
		GLint vertexColorLocation = glGetUniformLocation(shaderProgram, "outColor");
		glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);

		glBindVertexArray(VAO);
		//glDrawArrays(GL_TRIANGLES, 0, 3);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		glfwSwapBuffers(window);
	}

	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteBuffers(1, &EBO);

	glfwTerminate();

	return 0;
}