hw2p helper

threejs 2D template

by jmchen

HTML

<div id="info">THREE.JS 2D Template
    <br/>Left & right click to draw line</div>
<script src="http://cdnjs.cloudflare.com/ajax/libs/three.js/r70/three.min.js"></script>
<!-- the following disable the regular right-button click -->
<script type="text/javascript">
    document.oncontextmenu = function() {
        return false;
    }
</script>

CSS

#info {
    position: absolute;
    top: 0px;
    width: 100%;
    padding: 10px;
    text-align: center;
    color: #ffff00
}
body {
    overflow: hidden;
}

JavaScript

var camera, scene, renderer;
var mouse = new THREE.Vector2();
var cameraLeft = -50,
    cameraRight = 50,
    cameraTop = 50,
    cameraBottom = -50,
    cameraNear = -10,
    cameraFar = 10;

var leftPt, rightPt; // empty array
var line1, line2;

init();
animate();

function lineCoeff (p1,q1,p2,q2) {
	// ax + by + c = 0
    var a = q2 - q1;
    var b = p1 - p2;
    var c = p2*q1 - p1*q2;
    return [a,b,c];
}

function solve (coeff1, coeff2) {
    var a1 = coeff1[0], b1 = coeff1[1], c1 = coeff1[2];
    var a2 = coeff2[0], b2 = coeff2[1], c2 = coeff2[2];
    
    var denom = a2*b1 - a1*b2;
    
    var x = (b2*c1 - b1*c2)/denom;
    var y = -(a2*c1 - a1*c2)/denom;
    return [x,y];
}

function init() {
    scene = new THREE.Scene();

    camera = new THREE.OrthographicCamera(cameraLeft, cameraRight, cameraTop, cameraBottom, cameraNear, cameraFar);
    camera.position.z = 10;
    scene.add(camera);

    // draw border
    var material = new THREE.LineBasicMaterial({
        color: 0x0000ff
    });

    var geometry = new THREE.Geometry();
    geometry.vertices.push(
    new THREE.Vector3(-40, -40, 0),
    new THREE.Vector3(40, -40, 0),
    new THREE.Vector3(40, 40, 0),
    new THREE.Vector3(-40, 40, 0),
    new THREE.Vector3(-40, -40, 0));

    var border = new THREE.Line(geometry, material);
    scene.add(border);

    renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    renderer.setClearColor(0x888888);

    document.body.appendChild(renderer.domElement);
    window.addEventListener('resize', onWindowResize, false);
    window.addEventListener('mousedown', onDocumentMouseDown, false);
}

function onWindowResize() {
    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
    renderer.setSize(window.innerWidth, window.innerHeight);
}

function onDocumentMouseDown(event) {
    event.preventDefault();
    // Normalized Device Coordinate (NDC)
    // NDC: [-1,1]x[-1,1]
   ...