script.js

let renderer,
    camera,
    planet,
    moon,
    sphereBg,
    terrainGeometry,
    container = document.getElementById("canvas_container"),
    timeout_Debounce,
    frame = 0,
    cameraDx = 0.05,
    count = 0,
    t = 0;

/*   Lines values  */
let lineTotal = 1000;
let linesGeometry = new THREE.BufferGeometry();
linesGeometry.setAttribute("position", new THREE.BufferAttribute(new Float32Array(6 * lineTotal), 3));
linesGeometry.setAttribute("velocity", new THREE.BufferAttribute(new Float32Array(2 * lineTotal), 1));
let l_positionAttr = linesGeometry.getAttribute("position");
let l_vertex_Array = linesGeometry.getAttribute("position").array;
let l_velocity_Array = linesGeometry.getAttribute("velocity").array;


init();
animate();


function init() {
    scene = new THREE.Scene();
    scene.background = new THREE.Color("#000000");
    scene.fog = new THREE.Fog("#3c1e02", 0.5, 50);

    camera = new THREE.PerspectiveCamera(55, window.innerWidth / window.innerHeight, 0.01, 1000)
    camera.position.set(0, 1, 32)

    pointLight1 = new THREE.PointLight("#ffffff", 1, 0);
    pointLight1.position.set(0, 30, 30);
    scene.add(pointLight1);

    renderer = new THREE.WebGLRenderer({
        antialias: true,
        alpha: true
    });
    renderer.setSize(container.clientWidth, container.clientHeight);
    renderer.setPixelRatio(window.devicePixelRatio);
    container.appendChild(renderer.domElement);

    const loader = new THREE.TextureLoader();

    // Planet
    const texturePlanet = loader.load('https://i.ibb.co/h94JBXy/saturn3-ljge5g.jpg');
    texturePlanet.anisotropy = 16;
    const planetGeometry = new THREE.SphereBufferGeometry(10, 50, 50);
    const planetMaterial = new THREE.MeshLambertMaterial({
        map: texturePlanet,
        fog: false
    });
    planet = new THREE.Mesh(planetGeometry, planetMaterial);
    planet.position.set(0, 8, -30);
    scene.add(planet);


    //Moon
    const textureMoon = loader.load('https://i.ibb.co/64zn361/moon-ndengb.jpg');
    textureMoon.anisotropy = 16;
    let moonGeometry = new THREE.SphereBufferGeometry(2, 32, 32);
    let moonMaterial = new THREE.MeshPhongMaterial({
        map: textureMoon,
        fog: false
    });
    moon = new THREE.Mesh(moonGeometry, moonMaterial);
    moon.position.set(0, 8, 0);
    scene.add(moon);


    // Sphere Background 
    const textureSphereBg = loader.load('https://i.ibb.co/JCsHJpp/stars2-qx9prz.jpg');
    textureSphereBg.anisotropy = 16;
    const geometrySphereBg = new THREE.SphereBufferGeometry(150, 32, 32);
    const materialSphereBg = new THREE.MeshBasicMaterial({
        side: THREE.BackSide,
        map: textureSphereBg,
        fog: false
    });
    sphereBg = new THREE.Mesh(geometrySphereBg, materialSphereBg);
    sphereBg.position.set(0, 50, 0);
    scene.add(sphereBg);


    // Terrain
    const textureTerrain = loader.load();
    textureTerrain.rotation = THREE.MathUtils.degToRad(5);
    terrainGeometry = new THREE.PlaneBufferGeometry(70, 70, 20, 20);
    const terrainMaterial = new THREE.MeshBasicMaterial({
        map: textureTerrain,
        fog: true
    });
    terrain = new THREE.Mesh(terrainGeometry, terrainMaterial);
    terrain.rotation.x = -0.47 * Math.PI;
    terrain.rotation.z = THREE.Math.degToRad(90);
    scene.add(terrain);

    let t_vertex_Array = terrainGeometry.getAttribute("position").array;
    terrainGeometry.getAttribute("position").setUsage(THREE.DynamicDrawUsage);

    terrainGeometry.setAttribute("myZ", new THREE.BufferAttribute(new Float32Array(t_vertex_Array.length / 3), 1));
    let t_myZ_Array = terrainGeometry.getAttribute("myZ").array;

    for (let i = 0; i < t_vertex_Array.length; i++) {
        t_myZ_Array[i] = THREE.MathUtils.randInt(0, 5);
    }

    //Terain Lines
    const terrain_line = new THREE.LineSegments(
        terrainGeometry,
        new THREE.LineBasicMaterial({
            color: "#fff",
            fog: false
        })
    );
    terrain_line.rotation.x = -0.47 * Math.PI;
    terrain_line.rotation.z = THREE.Math.degToRad(90);
    scene.add(terrain_line);



    //  Stars
    for (let i = 0; i < lineTotal; i++) {
        let x = THREE.MathUtils.randInt(-100, 100);
        let y = THREE.MathUtils.randInt(10, 40);
        if (x < 7 && x > -7 && y < 20) x += 14;
        let z = THREE.MathUtils.randInt(0, -300);

        l_vertex_Array[6 * i + 0] = l_vertex_Array[6 * i + 3] = x;
        l_vertex_Array[6 * i + 1] = l_vertex_Array[6 * i + 4] = y;
        l_vertex_Array[6 * i + 2] = l_vertex_Array[6 * i + 5] = z;

        l_velocity_Array[2 * i] = l_velocity_Array[2 * i + 1] = 0;
    }
    let starsMaterial = new THREE.LineBasicMaterial({
        color: "#ffffff",
        transparent: true,
        opacity: 0.5,
        fog: false
    });
    let lines = new THREE.LineSegments(linesGeometry, starsMaterial);
    linesGeometry.getAttribute("position").setUsage(THREE.DynamicDrawUsage);
    scene.add(lines);
}




function animate() {
    planet.rotation.y += 0.002;
    sphereBg.rotation.x += 0.002;
    sphereBg.rotation.y += 0.002;
    sphereBg.rotation.z += 0.002;


    // Moon Animation
    moon.rotation.y -= 0.007;
    moon.rotation.x -= 0.007;
    moon.position.x = 15 * Math.cos(t) + 0;
    moon.position.z = 20 * Math.sin(t) - 35;
    t += 0.015;


    // Terrain Animation  
    let t_vertex_Array = terrainGeometry.getAttribute("position").array;
    let t_myZ_Array = terrainGeometry.getAttribute("myZ").array;

    for (let i = 0; i < t_vertex_Array.length; i++) {
        if (i >= 210 && i <= 250) t_vertex_Array[i * 3 + 2] = 0;
        else {
            t_vertex_Array[i * 3 + 2] = Math.sin((i + count * 0.0003)) * (t_myZ_Array[i] - (t_myZ_Array[i] * 0.5));
            count += 0.1;
        }
    }

    //   Stars Animation  
    for (let i = 0; i < lineTotal; i++) {
        l_velocity_Array[2 * i] += 0.0049;
        l_velocity_Array[2 * i + 1] += 0.005;

        l_vertex_Array[6 * i + 2] += l_velocity_Array[2 * i];
        l_vertex_Array[6 * i + 5] += l_velocity_Array[2 * i + 1];

        if (l_vertex_Array[6 * i + 2] > 50) {
            l_vertex_Array[6 * i + 2] = l_vertex_Array[6 * i + 5] = THREE.MathUtils.randInt(-200, 10);
            l_velocity_Array[2 * i] = 0;
            l_velocity_Array[2 * i + 1] = 0;
        }
    }


    //Camera Movement
    camera.position.x += cameraDx;
    camera.position.y = -1.2 * (1 - Math.abs(frame / 2000 - 0.5) / 0.5);
    camera.lookAt(0, 0, 0);
    frame += 8;
    if (frame > 2000) frame = 0;
    if (camera.position.x > 18) cameraDx = -cameraDx;
    if (camera.position.x < -18) cameraDx = Math.abs(cameraDx);


    l_positionAttr.needsUpdate = true;
    terrainGeometry.attributes.position.needsUpdate = true;
    renderer.render(scene, camera);
    requestAnimationFrame(animate);
}




/*     Resize     */
window.addEventListener("resize", () => {
    clearTimeout(timeout_Debounce);
    timeout_Debounce = setTimeout(onWindowResize, 80);
});
function onWindowResize() {
    camera.aspect = container.clientWidth / container.clientHeight;
    camera.updateProjectionMatrix();
    renderer.setSize(container.clientWidth, container.clientHeight);
}



/*     Fullscreen btn     */
let fullscreen;
let fsEnter = document.getElementById('fullscr');
fsEnter.addEventListener('click', function (e) {
    e.preventDefault();
    if (!fullscreen) {
        fullscreen = true;
        document.documentElement.requestFullscreen();
        fsEnter.innerHTML = "Exit Fullscreen";
    }
    else {
        fullscreen = false;
        document.exitFullscreen();
        fsEnter.innerHTML = "Go Fullscreen";
    }
});