Sky Shader and Post-Processing Issue

Based on the images you've shared, it appears you're experiencing a common issue when using the Sky object with EffectComposer for post-processing in Three.js.

Potential Causes

When using the Sky object with post-processing, there are a few common issues that can cause the distortion you're seeing:

1. Render Order: The Sky object might need special handling in the post-processing pipeline
2. Depth Information: Post-processing might be affecting the depth information needed by the Sky shader
3. Render Target Settings: The render targets used by EffectComposer might need specific configuration

Possible Solutions

Here are some approaches to resolve this issue:

1. Separate Rendering Pass for Sky:
   Try rendering the sky separately and then compositing it with your scene:

   JAVASCRIPTCopied
   // Render sky to a separate target
   renderer.setRenderTarget(skyRenderTarget);
   renderer.render(skyScene, camera);
   renderer.setRenderTarget(null);
   
   // Use the sky as a background in your post-processing chain
   // You might need a custom shader pass to composite them

2. Adjust EffectComposer Setup:
   Make sure your EffectComposer is properly configured:

   JAVASCRIPTCopied
   // Create a properly configured render target
   const renderTarget = new THREE.WebGLRenderTarget(
     window.innerWidth, 
     window.innerHeight, 
     {
       minFilter: THREE.LinearFilter,
       magFilter: THREE.LinearFilter,
       format: THREE.RGBAFormat,
       stencilBuffer: false,
       depthBuffer: true
     }
   );
   
   // Create composer with this target
   const composer = new EffectComposer(renderer, renderTarget);

3. Check Sky Object Configuration:
   Ensure your Sky object is properly configured and added to the scene:

   JAVASCRIPTCopied
   const sky = new Sky();
   sky.scale.setScalar(450000);
   scene.add(sky);
   
   // Make sure to set sky properties correctly
   const uniforms = sky.material.uniforms;
   uniforms['turbidity'].value = 10;
   uniforms['rayleigh'].value = 2;
   uniforms['mieCoefficient'].value = 0.005;
   uniforms['mieDirectionalG'].value = 0.8;

4. Render Order and Layers:
   Try adjusting the render order or using layers to control how the Sky is processed:

   JAVASCRIPTCopied
   sky.renderOrder = -1; // Render before other objects
   
   // Or use layers to control rendering
   sky.layers.set(1);
   camera.layers.enable(1);

If you could share more details about your specific EffectComposer setup and Sky implementation, I might be able to provide more targeted advice for your particular case.