OpenGL_读取外部shader、建立索引缓冲区

上次通过字符串的形式写了简单的顶点和片元着色器

这次优化为把shader放在外部，用类状态机的方式读取

为shader的编写带来了极大便利

见代码

#include<GL/glew.h>
#include <GLFW/glfw3.h>

#include<iostream>
#include<fstream>
#include<string>
#include<sstream>

struct ShaderProgramSource
{
	std::string VertexShader;
	std::string FragmentShader;
};
static ShaderProgramSource ParseShader(const std::string& filepath)
{
	std::ifstream stream(filepath);

	enum class ShaderType
	{
		NONE = -1, VERTEX = 0, FRAGMENT = 1
	};

	std::string line;
	std::stringstream ss[2];
	ShaderType type = ShaderType::NONE;
	while (getline(stream, line))
	{
		if (line.find("#shader") != std::string::npos)
		{
			if (line.find("vertex") != std::string::npos)
				type = ShaderType::VERTEX;
			else if (line.find("fragment") != std::string::npos)
				type = ShaderType::FRAGMENT;
		}
		else
		{
			ss[int(type)] << line << '\n';
		}
	}
	return{ ss[0].str(),ss[1].str() };
}
static unsigned int CompileShader(unsigned int type, const std::string& source)
{
	unsigned int id = glCreateShader(type);
	const char* src = source.c_str();
	glShaderSource(id, 1, &src, nullptr);
	glCompileShader(id);

	int result;
	glGetShaderiv(id, GL_COMPILE_STATUS, &result);
	if (result == GL_FALSE)
	{
		int length;
		glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
		char* message = (char*)alloca(length * sizeof(char));
		glGetShaderInfoLog(id, length, &length, message);
		std::cout << "Failed To Compile" << (type == GL_VERTEX_SHADER ? "vertex" : "fragmenrt") << " Shader Nya~" << std::endl;
		std::cout << message << std::endl;

		glDeleteShader(id);
		return 0;
	}
	return id;
}
static unsigned int CreateShader(const std::string& vertexShader, const std::string& fragmentShader)
{
	unsigned int program = glCreateProgram();
	unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
	unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

	glAttachShader(program, vs);
	glAttachShader(program, fs);
	glLinkProgram(program);
	glValidateProgram(program);

	glDeleteShader(vs);
	glDeleteShader(fs);

	return program;
}
int main(void)
{
	GLFWwindow* window;

	/* Initialize the library */
	if (!glfwInit())
		return -1;

	glewInit();

	/* Create a windowed mode window and its OpenGL context */
	window = glfwCreateWindow(640, 480, "OpenGl", NULL, NULL);
	if (!window)
	{
		glfwTerminate();
		return -1;
	}

	/* Make the window's context current */
	glfwMakeContextCurrent(window);

	if (glewInit() != GLEW_OK) {
		std::cout << "Error" << std::endl;
	}
	std::cout << glGetString(GL_VERSION) << std::endl;

	float position[] = {
		-0.5f, -0.5f,//0
		 0.5f, -0.5f,//1
		 0.5f,  0.5f,//2
		 -0.5f, 0.5f,//3
	};

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

	unsigned int buffer;
	glGenBuffers(1, &buffer);
	glBindBuffer(GL_ARRAY_BUFFER, buffer);
	glBufferData(GL_ARRAY_BUFFER, 2 * 6 * sizeof(float), position, GL_STATIC_DRAW);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);

	/*glbindbuffer(gl_array_buffer, 0);*/

	unsigned int ibo;//索引缓冲区对象,必须无符号整形
	glGenBuffers(1, &ibo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo);//索引缓冲区插槽
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6 * sizeof(unsigned int), indices, GL_STATIC_DRAW);

	ShaderProgramSource source = ParseShader("res/shaders/Basic.shader");
	std::cout << "VERREX" << std::endl;
	std::cout << source.VertexShader << std::endl;
	std::cout << "FRAGMENT" << std::endl;
	std::cout << source.FragmentShader << std::endl;

	unsigned int shader = CreateShader(source.VertexShader,source.FragmentShader);
	glUseProgram(shader);

	/* Loop until the user closes the window */
	while (!glfwWindowShouldClose(window))
	{
		/* Render here */
		glClear(GL_COLOR_BUFFER_BIT);

		glDrawElements(GL_TRIANGLES, 6,GL_UNSIGNED_INT, nullptr);

		/* Swap front and back buffers */
		glfwSwapBuffers(window);

		/* Poll for and process events */
		glfwPollEvents();
	}

	glDeleteProgram(shader);

	glfwTerminate();
	return 0;
}