javascript - Three.js不渲染，一定要有requestAnimationFrame吗？

Question

我正在做第 2 章 - WebGL Up and Running 书中的示例。

我想显示一个静态纹理映射的立方体。

此代码不起作用:

var camera = null,
renderer = null,
scene = null,
cube = null,
animating = false;

function onLoad() {
// Grab our container div
var container = document.getElementById("container");
// Create the Three.js renderer, add it to our div
renderer = new THREE.WebGLRenderer({
    antialias: true
});
renderer.setSize(container.offsetWidth, container.offsetHeight);
container.appendChild(renderer.domElement);
// Create a new Three.js scene
scene = new THREE.Scene();
// Put in a camera
camera = new THREE.PerspectiveCamera(45,
    container.offsetWidth / container.offsetHeight, 1, 4000);
camera.position.set(0, 0, 3);
// Create a directional light to show off the object
var light = new THREE.DirectionalLight(0xffffff, 1.5);
light.position.set(0, 0, 1);
scene.add(light);
// Create a shaded, texture-mapped cube and add it to the scene
// First, create the texture map
var mapUrl = "cuttherope.jpg";
var map = THREE.ImageUtils.loadTexture(mapUrl);
// Now, create a Phong material to show shading; pass in the map
var material = new THREE.MeshPhongMaterial({
    map: map
});
// Create the cube geometry
var geometry = new THREE.CubeGeometry(1, 1, 1);
// And put the geometry and material together into a mesh
cube = new THREE.Mesh(geometry, material);
// Turn it toward the scene, or we won't see the cube shape!
cube.rotation.x = Math.PI / 5;
cube.rotation.y = Math.PI / 5;
// Add the cube to our scene
scene.add(cube);
renderer.render(scene, camera);

}

但是在我添加 run 函数并调用 requestAnimationFrame 后，它显示了立方体

...
cube.rotation.x = Math.PI / 5;
cube.rotation.y = Math.PI / 5;
// Add the cube to our scene
scene.add(cube);
run();
}

function run() {
renderer.render(scene, camera);
requestAnimationFrame(run);

}

有人可以解释一下为什么吗？ 谢谢!

Answer 1

纹理(贴图)异步加载，因此在第一个示例中，当您调用 render() 时，纹理尚不可用。您需要有一个纹理加载回调来在加载图像时重新渲染，或者像您对 requestAnimationFrame 所做的那样，有一个连续的渲染循环。