1. three.js中使用CameraHelper来可视化调整阴影相机的范围

光源

const directionLight = new THREE.DirectionalLight(0xffffff, 1);
directionLight.position.set(100, 60, 20);
directionLight.castShadow = true;
scene.add(directionLight);

设置计算阴影的范围

directionLight.shadow.camera.left = 
directionLight.shadow.camera.top = 
directionLight.shadow.camera.bottom = 
directionLight.shadow.camera.right = 
directionLight.shadow.camera.near = 
directionLight.shadow.camera.far = 

有时候我们很难，调整好这个对应的数值，不过现在可以通过 CameraHelper来可视化调整这个阴影相机了

const cameraHelper = new THREE.CameraHelper(directionLight.shadow.camera);
scene.add(cameraHelper);

原则： 根据3D场景渲染范围，去设置.shadow.camera长方体的尺寸参数，一般要比渲染范围稍微大一些即可，过小阴影会导致不显示或者不完整，过大很大可能导致阴影模糊