EdgesGeometry是您正在寻找的：

function box(scene, x, y, z, size) {
      const points = [];

      let box_geometry = new THREE.BoxGeometry(size, size, size);
      var material = new THREE.MeshPhongMaterial();
      const box = new THREE.Mesh(box_geometry, material);
      /* Borders*/
      let borders_geo = new THREE.EdgesGeometry(box_geometry);
      const red_color = new THREE.Color(0x660505);
      const mat = new THREE.LineBasicMaterial({ color: red_color});
      let borders = new THREE.LineSegments(borders_geo, mat);
      borders.renderOrder = 1; // make sure borders are rendered 2nd
      box.add(borders)
      box.position.set(x, y, z);
      scene.add(box);
    }
    var scene = new THREE.Scene();

    let n = 5;
    let size = 8/n;
    let min = -4;
    for (let i = 0; i < n; i++) {
      for (let j = 0; j < n; j++) {
        let x = min + 8 * (i / n);
        let z = min +  8 * (j / n);
        box(scene, x, 0, z, size);
      }
    }

    var spotLight = new THREE.SpotLight(0xffffff);
    spotLight.position.set(5, 5, 5);
    scene.add(spotLight);

    spotLight = new THREE.SpotLight(0xffffff);
    spotLight.position.set(-5, 5, 5);
    scene.add(spotLight);

    var camera = new THREE.PerspectiveCamera(
      75,
      window.innerWidth / window.innerHeight,
      0.1,
      1000
    );
    var renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);
    document.body.appendChild(renderer.domElement);

    camera.position.set(1, 8, 4);
    camera.lookAt(scene.position);
    renderer.render(scene, camera);

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/0.148.0/three.min.js"></script>