Creating a Combined Day and Night Sky in Three.js

Based on the information available, here are some approaches to create a scene with both a daytime sky with sun and a nighttime moon simultaneously:

Approach 1: Using the Sky Object with Custom Elements

The Sky object in Three.js is primarily designed for creating realistic daytime skies with a sun. To add a moon to this setup:

1. Use the Sky object for the daytime portion
2. Create a separate moon object (could be a textured sphere) and position it in your scene
3. You may need to manage lighting carefully to ensure the moon appears appropriately lit

JAVASCRIPTCopied
// Create the Sky
const sky = new THREE.Sky();
sky.scale.setScalar(450000);
scene.add(sky);

// Configure the sun position and appearance
const sun = new THREE.Vector3();
const uniforms = sky.material.uniforms;
uniforms['turbidity'].value = 10;
uniforms['rayleigh'].value = 2;
uniforms['mieCoefficient'].value = 0.005;
uniforms['mieDirectionalG'].value = 0.8;

// Set sun position
const phi = THREE.MathUtils.degToRad(90 - parameters.elevation);
const theta = THREE.MathUtils.degToRad(parameters.azimuth);
sun.setFromSphericalCoords(1, phi, theta);
uniforms['sunPosition'].value.copy(sun);

// Create a moon
const moonGeometry = new THREE.SphereGeometry(5000, 32, 32);
const moonTexture = new THREE.TextureLoader().load('moon_texture.jpg');
const moonMaterial = new THREE.MeshStandardMaterial({ 
    map: moonTexture,
    emissive: 0x555555, // Give it a slight glow
    emissiveMap: moonTexture
});
const moon = new THREE.Mesh(moonGeometry, moonMaterial);

// Position the moon opposite to the sun
moon.position.set(-sun.x * 200000, sun.y * 100000, -sun.z * 200000);
scene.add(moon);

Approach 2: Custom Skybox with Both Elements

Another approach is to create a custom skybox that includes both day and night elements:

1. Create a custom cubemap texture that has both day and night elements
2. Apply this to a large cube or sphere surrounding your scene

Approach 3: Gradient Blend Between Two Skies

You could also create two separate sky domes and blend between them:

1. Create a daytime sky with the Sky object
2. Create a nighttime sky (either with another modified Sky object or a custom solution)
3. Use shader techniques to blend between the two based on position in the scene

Additional Considerations

• Lighting will be crucial - you may need directional lights for both the sun and moon
• Consider using a gradient or transition zone between day and night areas
• For the moon, you might want to add a subtle glow effect using post-processing

Since the specific implementation details for a combined day/night sky aren't explicitly covered in the core Three.js documentation, you might need to combine multiple techniques or explore community examples for the most effective solution.