重绘对象时如何清除屏幕

我正在尝试实现 boids 算法，一切都很顺利，直到使用 three.js 绘制鸟类（或立方体，在我的情况下）。

重绘后屏幕未清除，因此我什至会在屏幕上获得旧的立方体。

这是我的代码：

var scene;
var camera;
var aspect = window.innerWidth / window.innerHeight;

scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera( 45, aspect, 0.1, 1000 );
camera.position.z = 200;
var geometry = new THREE.BoxGeometry( 10, 10, 10 );
var loader = new THREE.TextureLoader();
function init()
{
    var posx, posy, posz;
    var velx, vely, velz;
    var rotx = 0;
    var roty = 0;
    var rotz = 0;
    var boid;
    loader.load('images/picture.jpg',   function ( texture ) {
            var material = new THREE.MeshBasicMaterial( {
                map: texture
            } );
            for ( var i = 0; i < 5; i ++ ) {
                posx = (Math.random() - 0.5) * 100;
                posy = (Math.random() - 0.5) * 100;
                posz = (Math.random() - 0.5) * 100;
                velx = (Math.random() - 0.7) * 100;
                vely = (Math.random() - 0.7) * 100;
                velz = (Math.random() - 0.7) * 100;
                var boidPosition = new THREE.Vector3(posx, posy, posz);
                var boidRotation = new THREE.Vector3(rotx, roty, rotz);
                var boidVelocity = new THREE.Vector3(velx, vely, velz);

                var boidDesign = new THREE.Mesh( geometry, material );
                boidDesign.position.x = boidPosition.x;
                boidDesign.position.y = boidPosition.y;
                boidDesign.position.z = boidPosition.z;
                boid = new Boid(boidPosition, boidVelocity);
                boids[i] = boid;
                boidDesign.name = "test_name" + i;
                scene.add( boidDesign );
            }
        },
        function ( xhr ) {
            console.log( (xhr.loaded / xhr.total * 100) + '% loaded' );
        },
        function ( xhr ) {
            console.log( 'An error happened' );
        }
    );
}

function redraw() {
    var boid;
    loader.load('images/picture.jpg',   function ( texture ) {
            var material = new THREE.MeshBasicMaterial( {
                map: texture
            } );
            for ( var i = 0; i < boids.length; i ++ ) {
                boid = boids[i];
                var boidPosition = new THREE.Vector3(boid.position.x, boid.position.y, boid.position.z);
                var boidDesign = new THREE.Mesh( geometry, material );
                boidDesign.position.x = boidPosition.x;
                boidDesign.position.y = boidPosition.y;
                boidDesign.position.z = boidPosition.z;
                boidDesign.name = "test_name" + i;
                scene.add( boidDesign );
            }
        },
        function ( xhr ) {
            console.log( (xhr.loaded / xhr.total * 100) + '% loaded' );
        },
        function ( xhr ) {
            console.log( 'An error happened' );
        }
    );
}
function removeEntity(object) {
    var selectedObject = scene.getObjectByName(object.name);
    scene.remove( selectedObject );
}
function drawAfterUpdate()
{
    var boid;
    for(var i = 0; i < boids.length; i++)
    {
        boid = boids[i];
        boid.update(boids);
        removeEntity(boid);
    }
    redraw(boids);
}
var renderer = new THREE.WebGLRenderer();
renderer.setSize( window.innerWidth, window.innerHeight );
renderer.setClearColor( 0x000000 );
document.body.appendChild( renderer.domElement );

var render = function()
{
    requestAnimationFrame( render );
    drawAfterUpdate();
    renderer.render( scene, camera );
};
init();
render();

我只是找不到解决方案。

如果需要更多详细信息，请询问。提前谢谢。:)