multi viewport

do we need scissor test?!

HTML

<div id="info">Multi-Viewports
    <br/>with Scissor Animation</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/98/three.min.js"></script>
<script src="https://cdn.rawgit.com/mrdoob/three.js/master/examples/js/controls/OrbitControls.js">
    
</script>

CSS

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

JavaScript

var camera, scene, renderer, geometry, material, mesh, light, controls;
var k = 0,
    sign = 1;

var cameraHUD, sceneHUD;

console.log('init');
init();
animate();

function initHUD() {
    sceneHUD = new THREE.Scene();
    cameraHUD = new THREE.OrthographicCamera(-10.5, 10.5, 10.5, -10.5, -10, 10);
    cameraHUD.position.z = 5;
    sceneHUD.add(cameraHUD);

    var lineGeometry = new THREE.Geometry();
    lineGeometry.vertices.push(new THREE.Vector3(-10, -10,0),
    new THREE.Vector3(10, -10,0),
    new THREE.Vector3(10, 10,0),
    new THREE.Vector3(-10, 10,0),
    new THREE.Vector3(-10, -10, 0));
    var line = new THREE.Line(lineGeometry,
    new THREE.LineBasicMaterial({
        color: 0xffffff
    }));
    sceneHUD.add(line);
}

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

    camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 1000);
    camera.position.z = 500;
    scene.add(camera);

    geometry = new THREE.BoxGeometry(100, 20, 20);
    material = new THREE.MeshLambertMaterial();

    mesh = new THREE.Mesh(geometry, material);
    scene.add(mesh);

    light = new THREE.PointLight(0xffffff);
    light.position.set(100, 300, 200);
    scene.add(light);

    var gridXZ = new THREE.GridHelper(100, 10, 0xff0000, 0xffffff);
    scene.add(gridXZ);

    renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    renderer.setClearColor(0x888800);
    renderer.autoClear = false;

   // controls = new THREE.OrbitControls(camera, renderer.domElement);

    document.body.appendChild(renderer.domElement);
}

function animate() {
    //controls.update();

    requestAnimationFrame(animate);
    render();
}

function myclamp(x, lo, hi) {
    return x < lo ? lo : (x > hi ? hi : x);
}

function render() {
    var WW = window.innerWidth;
    var HH = window.innerHeight;

    k += 1 * sign;
    if (k < 0 || k > WW / 2) sign *= -1;
    k = myclamp(k, 0, WW / 2);

   ...