在three.js中如何让球体上的光线变得锐利？

我有一个简单的three.js场景，里面有球体和方向光。在球体上，你可以看到它逐渐变暗。如何使光到暗的过渡更快。如何让光更 “锐利”？

var scene, camera, renderer, controls, sphere, geometry, material, light;

scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.x = 3;
camera.position.z = 6;
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setClearColor(0xffffff, 1);
document.body.appendChild(renderer.domElement);

geometry = new THREE.SphereGeometry(1, 32, 32);
material = new THREE.MeshPhongMaterial({
  color: 0x777777
});
sphere = new THREE.Mesh(geometry, material);
scene.add(sphere);

light = new THREE.DirectionalLight(0xffffff, 1);
light.position.set(0, 10, 10);
scene.add(light);

renderer.render(scene, camera);

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r83/three.js"></script>

解决方案：

实现预期效果的一种方法是通过toon shading。因此，给 网格卡通材料 试试。你也可以定义一个 梯度图 定义了材料的不同照明区域。

var scene, camera, renderer, controls, sphere, geometry, material, light;

scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.x = 3;
camera.position.z = 6;
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setClearColor(0xffffff, 1);
document.body.appendChild(renderer.domElement);

geometry = new THREE.SphereGeometry(1, 32, 32);
material = new THREE.MeshToonMaterial({
  color: 0x777777
});
sphere = new THREE.Mesh(geometry, material);
scene.add(sphere);

light = new THREE.DirectionalLight(0xffffff, 1);
light.position.set(0, 10, 10);
scene.add(light);

renderer.render(scene, camera);

<script src="https://cdn.jsdelivr.net/npm/three@0.115/build/three.js"></script>