跟上一篇的不同是對uniform全域性屬性的理解

#include <glad\glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);

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

//片段著色器使用全域性的uniform輸出顏色值
const char* fragmentShaderSrc = "#version 330 core\n"
"out vec4 FragColor;\n"
"uniform vec4 GlobalColor;\n"
"void main(){\n"
"FragColor = GlobalColor;"
"}\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);

#ifdef __APPLE__
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif

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

	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		return -1;
	}

	//建立頂點著色器
	int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSrc, NULL);
	int success;
	char infoLog[512];
	glCompileShader(vertexShader);
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "GL COMPILE VERTEXSHADER : " << infoLog << std::endl;
	  
	}


	//建立片段著色器
	int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSrc, NULL);
	glCompileShader(fragmentShader);
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "GL COMPILE VERTEXSHADER2 : " << infoLog << std::endl;
	}


	//建立著色器程式
	int shaderPrograme = glCreateProgram();
	glAttachShader(shaderPrograme, vertexShader);
	glAttachShader(shaderPrograme, fragmentShader);
	glLinkProgram(shaderPrograme);
	glGetProgramiv(shaderPrograme, GL_LINK_STATUS, &success);
	if (!success)
	{
		glGetProgramInfoLog(shaderPrograme, 512, NULL, infoLog);
		std::cout << "GL LINK ERR : " << infoLog << std::endl;
	}

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	float firstTrangle[] = {
	    -0.5f,-0.5f,0.0f,
		0.5f,-0.5f,0.0f,
		0.0f,0.5f,0.0f
	};

	unsigned int VAO, VBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);

	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(firstTrangle), firstTrangle, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);


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

		glUseProgram(shaderPrograme);
		glBindVertexArray(VAO);
		//設定全域性uniform欄位
		float timeValue = glfwGetTime();
		float greenValue = sin(timeValue) / 2.0f + 0.5f;
		//找到uniform欄位位置
		int globalColorPosition = glGetUniformLocation(shaderPrograme, "GlobalColor");
		glUniform4f(globalColorPosition, 0.0f, greenValue, 0.0f, 1.0f);

		glDrawArrays(GL_TRIANGLES, 0, 3);

		glfwSwapBuffers(window);
		glfwPollEvents();

	}

	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glfwTerminate();
	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);
}
 

效果圖