Three.js Sun Position Control with Shadows

Based on the information you've shared, you're demonstrating a Three.js implementation that controls a directional light (representing the sun) over a 3D Google Map. This is an interesting application of Three.js lighting and shadow capabilities.

Key Components

From what you've described, your implementation includes:

1. Directional Light: Used to simulate sunlight with controllable position
2. Azimuth/Altitude Controls: For adjusting the sun's position in the sky
3. Intensity Control: For adjusting the brightness of the light
4. Shadow Material: Used to create realistic shadows on the map

Shadow Implementation

The use of Three.js's ShadowMaterial is particularly clever for this application. This material is specifically designed to receive shadows but be invisible otherwise, making it perfect for creating shadow effects on the map without interfering with the map's appearance.

Implementation Considerations

When implementing this type of sun position control with shadows in Three.js, you would typically need to:

1. Enable shadows in your renderer:

JAVASCRIPTCopied
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap; // for softer shadows

2. Configure your directional light to cast shadows:

JAVASCRIPTCopied
const sunLight = new THREE.DirectionalLight(0xffffff, 1.0);
sunLight.castShadow = true;
sunLight.shadow.mapSize.width = 1024;
sunLight.shadow.mapSize.height = 1024;
// Set appropriate shadow camera parameters based on your scene size
sunLight.shadow.camera.near = 0.5;
sunLight.shadow.camera.far = 500;
sunLight.shadow.camera.left = -100;
sunLight.shadow.camera.right = 100;
sunLight.shadow.camera.top = 100;
sunLight.shadow.camera.bottom = -100;
scene.add(sunLight);

3. Create a shadow-receiving plane with ShadowMaterial:

JAVASCRIPTCopied
const shadowMaterial = new THREE.ShadowMaterial();
shadowMaterial.opacity = 0.5; // Adjust based on light intensity
const shadowPlane = new THREE.Mesh(
  new THREE.PlaneGeometry(500, 500),
  shadowMaterial
);
shadowPlane.receiveShadow = true;
shadowPlane.rotation.x = -Math.PI / 2; // Rotate to be horizontal
scene.add(shadowPlane);

4. Update the sun position based on azimuth and altitude:

JAVASCRIPTCopied
function updateSunPosition(azimuth, altitude) {
  // Convert from spherical to Cartesian coordinates
  const phi = THREE.MathUtils.degToRad(90 - altitude);
  const theta = THREE.MathUtils.degToRad(azimuth);
  
  sunLight.position.x = Math.sin(phi) * Math.cos(theta);
  sunLight.position.y = Math.cos(phi);
  sunLight.position.z = Math.sin(phi) * Math.sin(theta);
  
  // Normalize and scale as needed
  sunLight.position.multiplyScalar(50);
}

5. Link the light intensity to shadow opacity for a more realistic effect:

JAVASCRIPTCopied
function updateLightIntensity(intensity) {
  sunLight.intensity = intensity;
  shadowMaterial.opacity = intensity * 0.5; // Scale shadow opacity with light intensity
}

This approach creates a realistic sun lighting effect with appropriate shadows that respond to the sun's position and intensity.