LearnOpenGL1.3：着色器

存在问题：

        1.glDrawElements的偏移量不能乱改。。。

        2.GLSL没提示老是写错

#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

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

const unsigned int HEIGHT = 600;
const unsigned int WIDTH = 800;

// shader
const char* vertexShaderSource = "#version 330 core\n"
	"layout (location = 0) in vec3 aPos;\n"
	"layout (location = 1) in vec3 aColor;\n"
	"out vec3 ourColor;\n"
	"void main()\n"
	"{\n"
	"	gl_Position = vec4(aPos, 1.0);\n"
	"	ourColor = aColor;\n"
	"}\0";
	
const char *fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "in vec3 ourColor;\n"
    "void main()\n"
    "{\n"
    "   FragColor = vec4(ourColor, 1.0);\n"
    "}\n\0";



int main() {
	// 配置
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	// MacOSX
	//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);


	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL) {
		std::cout << "Failed to create GLFW window" << std::endl;
		return -1;
	}
	// 设置当前线程的主上下文
	glfwMakeContextCurrent(window);
	glfwSetFramebufferSizeCallback(window, frambuffer_size_callback);

	// glad管理函数指针
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
		std::cout << "Failed to initialize GLAD" << std::endl;
		return -1;
	}

	// 坐标转换
	//glViewport(0, 0, HEIGHT, HEIGHT);

	unsigned int vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	// 动态编译
	glCompileShader(vertexShader);

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

	// link
	unsigned int shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	//float vertices[] = {
	//-0.5f,-0.5f,0.0f,
	//0.5f,-0.5f,0.0f,
	//0.0f,0.5f,0.0f,

	//0.5f,-0.5f,0.0f,
	//1.0f,0.5f,0.0f,
	//0.0f,0.5f,0.0f,
	//};

	// 使用索引缓冲区
	float vertices[] = {
		// 位置			// 颜色
		0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f,// 右上角
		0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, // 右下角
		-0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, // 左下角
		-0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 0.0f,  // 左上角
	};


	unsigned int indices[] =
	{
		0, 1, 3,
		1, 2, 3
	};

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

	glBindVertexArray(VAO);

	// bind to target
	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	// copy vertices to gpu
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	unsigned int EBO;
	glGenBuffers(1, &EBO);

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


	// 告知opengl如何解析
	// 位置属性  0为layout=0
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)0);
	// 启用顶点属性
	glEnableVertexAttribArray(0);
	// 颜色属性  最后一个参数为offset
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)(3*sizeof(float)));
	glEnableVertexAttribArray(1);


	// 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);
	// shader很少变化，所以不是动态改变的也行
	//glUseProgram(shaderProgram);
	// 
    // render
	while (!glfwWindowShouldClose(window)) {

		processInput(window);

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		glUseProgram(shaderProgram);

		// ourColor随着时间变化
		//float timeValue = glfwGetTime();
		 0-1  不知道为啥这么写
		//float newColorValue = (sin(timeValue) / 2.0f) + 0.5f;
		 查询位置值
		//int vertextColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
		 设置
		//glUniform4f(vertextColorLocation, 1.0f, newColorValue, 0.0f, 1.0f);

		glBindVertexArray(VAO);
		glDrawArrays(GL_TRIANGLES, 0, 6);

		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
		// 代替glDrawArrays   0：指定EBO中的偏移量
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		glfwSwapBuffers(window);
		// 检查事件，调用对应的回调函数
		glfwPollEvents();
	}

	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);
	// 释放/删除资源
	glfwTerminate();


	return 0;
}

void frambuffer_size_callback(GLFWwindow* window, int width, int height) {
	glViewport(0, 0, HEIGHT, HEIGHT);
}

void processInput(GLFWwindow* window) {
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
		glfwSetWindowShouldClose(window, true);
}

运行结果：