hw2p helper

threejs 2D template

by KUO YOU-TING

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 pa_x, pa_y, pb_x, pb_y, pc_x, pc_y, pd_x, pd_y;
//[pa_x, pa_y],[pb_x, pb_y]為第一個方程式的兩個點；[pc_x, pc_y], [pd_x, pd_y]為第二個方程式的兩個點
var count = 0; //計數，加到2時為圖中有兩線，顯示交點，顯示完後歸零

init();
animate();

function FindCoefficient (p1,q1,p2,q2) { //依給的點與Maxima結果求出方程式
    var x1 = q2-q1;
    var x2 = p1-p2;
    var x3 = p2*q1-p1*q2;
    console.log (x1 + ", " + x2 + ", " + x3);
    return [x1,x2,x3];
    
}

function Point (p1,q1,p2,q2,a1,b1,a2,b2) { 
//前4個輸入(2個點)為第一個方程式，後4個輸入(2個點)為第二個方程式，再依Maxima結果求交點
    var e1 = FindCoefficient (p1,q1,p2,q2);
    var e2 = FindCoefficient (a1,b1,a2,b2);
    
    var use = e2[0]*e1[1]-e1[0]*e2[1];
    var x = (e2[1]*e1[2]-e1[1]*e2[2])/use;
    var y = -(e2[0]*e1[2]-e1[0]*e2[2])/use;
    
    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 =...