Instanced mesh

import * as THREE from 'three';
const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setPixelRatio(Math.min(devicePixelRatio, 2));
document.body.appendChild(renderer.domElement);
const scene = new THREE.Scene();
scene.background = new THREE.Color(0x0a0a14);
const camera = new THREE.PerspectiveCamera(45, 1, 0.1, 100);
camera.position.set(4.2, 3.6, 4.2);
camera.lookAt(0, 0, 0);
const dLight = new THREE.DirectionalLight(0xffffff, 1.3);
dLight.position.set(3, 5, 2);
scene.add(dLight);
scene.add(new THREE.AmbientLight(0x404060, 1.2));

const GRID = 18;
const COUNT = GRID * GRID;
const geo = new THREE.BoxGeometry(0.32, 0.32, 0.32);
const mat = new THREE.MeshStandardMaterial({ roughness: 0.45, metalness: 0.1 });
const mesh = new THREE.InstancedMesh(geo, mat, COUNT);
const dummy = new THREE.Object3D();
const color = new THREE.Color();
let i = 0;
for (let x = 0; x < GRID; x++) {
  for (let z = 0; z < GRID; z++) {
    const px = (x - (GRID - 1) / 2) * 0.42;
    const pz = (z - (GRID - 1) / 2) * 0.42;
    color.setHSL(0.58 + (px + pz) * 0.01, 0.7, 0.6);
    mesh.setColorAt(i, color);
    i++;
  }
}
scene.add(mesh);

function resize() { renderer.setSize(innerWidth, innerHeight); camera.aspect = innerWidth / innerHeight; camera.updateProjectionMatrix(); }
addEventListener('resize', resize); resize();
renderer.setAnimationLoop((t) => {
  const time = t * 0.001;
  let idx = 0;
  for (let x = 0; x < GRID; x++) {
    for (let z = 0; z < GRID; z++) {
      const px = (x - (GRID - 1) / 2) * 0.42;
      const pz = (z - (GRID - 1) / 2) * 0.42;
      const h = Math.sin(time * 1.6 + (px + pz) * 1.4) * 0.35 + 0.4;
      dummy.position.set(px, h, pz);
      dummy.updateMatrix();
      mesh.setMatrixAt(idx, dummy.matrix);
      idx++;
    }
  }
  mesh.instanceMatrix.needsUpdate = true;
  mesh.rotation.y = time * 0.12;
  renderer.render(scene, camera);
});