How to use Code in my own code

[abingandabong]

I have a question about incorporating the code into my own code. I am making a flight simulator and I am trying to use this terrain for the game. this is my code so far:

import * as THREE from 'three';
import { GLTFLoader } from 'three/addons/loaders/GLTFLoader.js';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

// Scene setup
const loader = new GLTFLoader();
const scene = new THREE.Scene();

const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 100000);
camera.position.set(0, 20, 100);
scene.add(camera);

const light = new THREE.AmbientLight(0xffffff); // White light
scene.add(light);

const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setClearColor(0x87CEEB); // Light blue background
document.body.appendChild(renderer.domElement);

// Initialize OrbitControls
const controls = new OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.05;
controls.screenSpacePanning = false;
controls.maxPolarAngle = Math.PI / 2;
controls.update();

let plane;
const speed = 0.5; // Plane speed
const raycaster = new THREE.Raycaster();
const mouse = new THREE.Vector2();

// Variables to manage tilt
let isTiltingUp = false;
let isTiltingDown = false;
const tiltSpeed = 0.01; // Speed of tilt

// Load the plane model
loader.load('plane.gltf', function (gltf) {
plane = gltf.scene;
scene.add(plane);

plane.position.set(0, 10, -900);
plane.rotation.y = Math.PI / 2;

camera.position.set(20, 15, 50);
controls.target.copy(plane.position);
controls.update();

}, undefined, function (error) {
console.error(error);
});

// Add a crosshair canvas
const crosshairCanvas = document.createElement('canvas');
crosshairCanvas.style.position = 'absolute';
crosshairCanvas.style.top = '0';
crosshairCanvas.style.left = '0';
crosshairCanvas.style.pointerEvents = 'none'; // Allow mouse events to pass through
crosshairCanvas.width = window.innerWidth;
crosshairCanvas.height = window.innerHeight;
document.body.appendChild(crosshairCanvas);

const crosshairContext = crosshairCanvas.getContext('2d');

// Draw a fighter jet-style crosshair
function drawCrosshair(x, y) {
crosshairContext.clearRect(0, 0, crosshairCanvas.width, crosshairCanvas.height);

const size = 20; // Crosshair size
const lineWidth = 2; // Crosshair line width
const color = 'red';

crosshairContext.strokeStyle = color;
crosshairContext.lineWidth = lineWidth;

// Draw horizontal line
crosshairContext.beginPath();
crosshairContext.moveTo(x - size, y);
crosshairContext.lineTo(x + size, y);
crosshairContext.stroke();

// Draw vertical line
crosshairContext.beginPath();
crosshairContext.moveTo(x, y - size);
crosshairContext.lineTo(x, y + size);
crosshairContext.stroke();

// Draw center circle
crosshairContext.beginPath();
crosshairContext.arc(x, y, size / 2, 0, 2 * Math.PI);
crosshairContext.stroke();

}

// Update mouse position from crosshair
function updateMouseFromCrosshair(x, y) {
mouse.x = (x / window.innerWidth) * 2 - 1; // Normalize X
mouse.y = -(y / window.innerHeight) * 2 + 1; // Normalize Y
}

// Handle mouse movement
document.addEventListener('mousemove', (event) => {
const x = event.clientX;
const y = event.clientY;
drawCrosshair(x, y);
updateMouseFromCrosshair(x, y);
});

// Function to apply tilt to the plane
function applyTilt() {
if (!plane) return;

if (isTiltingUp) {
    plane.rotation.x += tiltSpeed; // Tilt up
}

if (isTiltingDown) {
    plane.rotation.x -= tiltSpeed; // Tilt down
}

// Clamp tilt to prevent flipping
plane.rotation.x = THREE.MathUtils.clamp(plane.rotation.x, -Math.PI / 6, Math.PI / 6);

}

// Move the plane towards the crosshair
function movePlaneTowardsCrosshair() {
if (!plane) return;

// Cast a ray from the camera through the mouse position
raycaster.setFromCamera(mouse, camera);

// Get the direction the crosshair is pointing
const direction = raycaster.ray.direction.clone();
direction.normalize();

// Orient the plane towards the target direction
plane.lookAt(plane.position.clone().add(direction));

// Apply tilt
applyTilt();

// Move the plane forward in the direction it's facing
plane.translateX(-speed); // Move along the local forward direction

}

// Handle keyboard controls for tilting
document.addEventListener('keydown', (event) => {
if (event.key === 'ArrowDown') {
isTiltingUp = true;
} else if (event.key === 'ArrowUp') {
isTiltingDown = true;
} else if (event.key === 'r') {
renderer.setAnimationLoop(() => {
movePlaneTowardsCrosshair(); // Move plane and apply tilt
controls.target.copy(plane.position); // Keep camera on plane
controls.update();
renderer.render(scene, camera);
});
}
});

document.addEventListener('keyup', (event) => {
if (event.key === 'ArrowDown') {
isTiltingUp = false;
} else if (event.key === 'ArrowUp') {
isTiltingDown = false;
} else if (event.key === 'a') {
renderer.setAnimationLoop(() => {
controls.target.copy(plane.position); // Keep camera on plane
controls.update();
renderer.render(scene, camera);
});
}
});

// Handle window resize
window.addEventListener('resize', () => {
renderer.setSize(window.innerWidth, window.innerHeight);
crosshairCanvas.width = window.innerWidth;
crosshairCanvas.height = window.innerHeight;

camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();

});

I want to add the code you provided:

// Generate a terrain
var xS = 63, yS = 63;
terrainScene = THREE.Terrain({
easing: THREE.Terrain.Linear,
frequency: 2.5,
heightmap: THREE.Terrain.DiamondSquare,
material: new THREE.MeshBasicMaterial({color: 0x5566aa}),
maxHeight: 100,
minHeight: -100,
steps: 1,
xSegments: xS,
xSize: 1024,
ySegments: yS,
ySize: 1024,
});
// Assuming you already have your global scene, add the terrain to it
scene.add(terrainScene);

// Optional:
// Get the geometry of the terrain across which you want to scatter meshes
var geo = terrainScene.children[0].geometry;
// Add randomly distributed foliage
decoScene = THREE.Terrain.ScatterMeshes(geo, {
mesh: new THREE.Mesh(new THREE.CylinderGeometry(2, 2, 12, 6)),
w: xS,
h: yS,
spread: 0.02,
randomness: Math.random,
});
terrainScene.add(decoScene);

to it. It just gives me a blank screen when I try. Do I need to import the module in my three js code? I already did npm install three.terrain.js? it would be great if you could give me the code and tell me what to improve if u have time thanks in advance :)