Troubleshooting Shadows in Three.js

Based on the information available, here are some common issues and troubleshooting tips for getting shadows to work properly in Three.js:

Essential Shadow Setup Checklist

1. Enable shadows in the renderer:

   JAVASCRIPTCopied
   renderer.shadowMap.enabled = true;
   // Optional: Set shadow map type
   renderer.shadowMap.type = THREE.PCFSoftShadowMap; // or other types

2. Enable shadows for each light that should cast shadows:

   JAVASCRIPTCopied
   light.castShadow = true;

3. Configure shadow properties for the light:

   JAVASCRIPTCopied
   // For DirectionalLight or SpotLight
   light.shadow.mapSize.width = 1024;  // Higher resolution = better quality
   light.shadow.mapSize.height = 1024;
   light.shadow.camera.near = 0.5;
   light.shadow.camera.far = 500;
   
   // For DirectionalLight specifically
   light.shadow.camera.left = -10;
   light.shadow.camera.right = 10;
   light.shadow.camera.top = 10;
   light.shadow.camera.bottom = -10;

4. Set objects to cast and/or receive shadows:

   JAVASCRIPTCopied
   // For objects that cast shadows
   object.castShadow = true;
   
   // For objects that receive shadows
   object.receiveShadow = true;

Common Issues to Check

1. Light position: Make sure your light is positioned correctly to cast shadows onto your objects.

2. Shadow camera frustum: For directional lights, ensure the shadow camera's frustum (left, right, top, bottom) is large enough to contain your objects.

3. Shadow bias: If you're seeing strange patterns or "shadow acne":

   JAVASCRIPTCopied
   light.shadow.bias = -0.001; // Adjust this value as needed

4. Material compatibility: Some materials don't work well with shadows. Make sure you're using materials that support shadows (like MeshStandardMaterial or MeshPhongMaterial).

5. Shadow map size: Increase the shadow map resolution for better quality:

   JAVASCRIPTCopied
   light.shadow.mapSize.width = 2048;
   light.shadow.mapSize.height = 2048;

6. Light intensity: If your light is too weak, shadows might not be visible.

7. Scene scale: If your scene is very large or very small, you might need to adjust the shadow camera's near and far values.

For specific shadow types, you'll need to use the appropriate shadow class based on your light type:

• PointLightShadow for PointLight
• DirectionalLightShadow for DirectionalLight
• SpotLightShadow for SpotLight

These shadow classes handle the specific shadow behavior for each light type.