基于HT for Web 3D呈现Box2DJS物理引擎

function init() {
    dm = new ht.DataModel();
    g3d = new ht.graph3d.Graph3dView(dm);
    g3d.setGridVisible(true);
    g3d.addToDOM();
    g3d.setEye(100, 50, 150);

    // Define the world
    var gravity = new b2Vec2(0, -100);
    var doSleep = false;
    world = new b2World(gravity, doSleep);

    createNode([0, -3, 0], [100, 6, 100], false, 0);
    createNode([-100, -50, 0], [400, 6, 100], false, -Math.PI/8);
    createNode([100, -50, 0], [50, 6, 100], false, Math.PI/6);

    createNode([1, 50, 0], [10, 10, 10], true);
    createNode([-1, 90, 0], [10, 10, 10], true);

    render();
}

function createNode(p3, s3, dynamic, angle) {
    var node = new ht.Node();
    node.p3(p3);
    node.s3(s3);               
    node.setRotationZ(angle == null ? Math.PI * Math.random() : angle);
    dm.add(node);

    var fixDef = new b2FixtureDef();
    if (dynamic) {
        fixDef.density = 0.5;
        fixDef.friction = 0.5;
        fixDef.restitution = 0.5;                    
        node.s({
            ‘all.color‘: ‘red‘,
            ‘batch‘: ‘dynamic‘
        });
    } else {
        fixDef.density = 0.0;                    
    }

    var shape = new b2PolygonShape();
    shape.SetAsBox(s3[0] / 2, s3[1] / 2);
    fixDef.shape = shape;

    var bodyDef = new b2BodyDef();
    bodyDef.type = dynamic ? b2Body.b2_dynamicBody : b2Body.b2_staticBody;
    bodyDef.position.Set(p3[0], p3[1]);
    bodyDef.angle = node.getRotationZ();
    bodyDef.userData = node;

    world.CreateBody(bodyDef).CreateFixture(fixDef);
}

count = 0
function render() {
    count++;
    if(count % 10 === 0){
        createNode([-1, 50, 0], [10, 10, 10], true);
    }                
    world.Step(1 / 60, 10, 10);
    var list = world.GetBodyList();
    while (list) {                                              
        var node = list.m_userData;
        if(node){
            var position = list.GetPosition();
            if(position.y < -150 || g3d.isSelected(node)){
                dm.remove(node);
                world.DestroyBody(list);
            }else{
                node.p3(position.x, position.y, 0);
                node.setRotationZ(list.GetAngle());                            
            }                                              
        }                    
        list = list.GetNext();
    }                    
    requestAnimationFrame(render);
}