"use strict"; // 參考 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode
////////////////////////////////////////////////////////////////////////////////
// 正多邊形產生器作業
// 你的作業是完成函式 PolygonGeometry(sides)
// 函式接收 1 個參數：
//   sides － 多邊形有多少邊
// 回傳使用最少三角型繪製的多邊形網格
// 多邊形半徑是 1。多邊形中心在 0, 0
////////////////////////////////////////////////////////////////////////////////

var camera, scene, renderer;
var windowScale;

function PolygonGeometry(sides) {
	var geo = new THREE.Geometry();

// 產生頂點
	for ( var pt = 0 ; pt < sides; pt++ )
	{
		// 加 90 度使我們從 +Y 軸開始，逆時針旋轉
		var angle = (Math.PI/2) + (pt / sides) * 2 * Math.PI;

var x = Math.cos( angle );
		var y = Math.sin( angle );

// 你的程式在這裡
		// 填入儲存頂點位置的程式

}
	// 你的程式在這裡
	// 寫程式產生組成多邊形的最少三角型集合

// 回傳幾何物件
	return geo;
}

function init() {
	var canvasWidth = window.innerWidth;
	var canvasHeight = window.innerHeight;
	var canvasRatio = canvasWidth / canvasHeight;

// 場景
	scene = new THREE.Scene();

// 攝影機：Y 上，X 右，Z 前
	windowScale = 4;
	var windowWidth = windowScale * canvasRatio;
	var windowHeight = windowScale;

camera = new THREE.OrthographicCamera( windowWidth / - 2, windowWidth / 2, windowHeight / 2, windowHeight / - 2, 0, 40 );

var focus = new THREE.Vector3( 0,1,0 );
	camera.position.x = focus.x;
	camera.position.y = focus.y;
	camera.position.z = 10;
	camera.lookAt(focus);

renderer = new THREE.WebGLRenderer({ antialias: false, preserveDrawingBuffer: true});
	renderer.gammaInput = true;
	renderer.gammaOutput = true;
	renderer.setSize( canvasWidth, canvasHeight );
	renderer.setClearColorHex( 0xFFFFFF, 1.0 );

}

function addToDOM() {
	var container = document.getElementById('container');
	var canvas = container.getElementsByTagName('canvas');
	if (canvas.length>0) {
		container.removeChild(canvas[0]);
	}
	container.appendChild( renderer.domElement );

}
function render() {
	renderer.render( scene, camera );
}

// 腳本本體
document.addEventListener("DOMContentLoaded", function () {
	try {
		init();
		showGrids();
		var geo = PolygonGeometry(5);
		var material = new THREE.MeshBasicMaterial( { color: 0xff0000, side: THREE.FrontSide } );
		var mesh = new THREE.Mesh( geo, material );
		scene.add( mesh );
		addToDOM();
		render();
	} catch(e) {
		var errorReport = "Your program encountered an unrecoverable error, can not draw on canvas. Error was:<br/><br/>";
		$('#container').append(errorReport+e);
	}
})