Selective Bloom Effect for Objects Behind Glass in Three.js

Based on the available information, applying a bloom effect specifically to materials behind glass requires a custom approach using Three.js post-processing capabilities.

The standard approach would be to use the EffectComposer with selective rendering. However, your example code doesn't align with how Three.js implements bloom effects.

Recommended Approach

To achieve a selective bloom effect for objects behind glass in Three.js:

1. Use the EffectComposer for post-processing
2. Implement selective rendering using layers or render targets
3. Apply the bloom effect only to specific objects

Here's a conceptual implementation in Three.js:

JAVASCRIPTCopied
// Set up renderer and scenes
const renderer = new THREE.WebGLRenderer();
const mainScene = new THREE.Scene();
const bloomScene = new THREE.Scene();

// Create your glass object in the main scene
const glass = new THREE.Mesh(
  new THREE.BoxGeometry(1, 1, 0.1),
  new THREE.MeshStandardMaterial({ transparent: true, opacity: 0.2 })
);
mainScene.add(glass);

// Add objects that should bloom when behind glass to both scenes
const objectBehindGlass = new THREE.Mesh(
  new THREE.SphereGeometry(0.5),
  new THREE.MeshStandardMaterial({ emissive: 0xff0000, emissiveIntensity: 1 })
);
objectBehindGlass.position.z = -1; // Position behind glass
mainScene.add(objectBehindGlass.clone());
bloomScene.add(objectBehindGlass);

// Set up EffectComposer
const composer = new THREE.EffectComposer(renderer);
composer.addPass(new THREE.RenderPass(mainScene, camera));

// Create a bloom pass for the bloom scene
const bloomPass = new THREE.UnrealBloomPass(
  new THREE.Vector2(window.innerWidth, window.innerHeight),
  1.5, // intensity
  0.4, // radius
  0.85 // threshold
);

// Add a custom pass to combine the bloom with the main scene
const bloomCompositePass = new THREE.ShaderPass(
  new THREE.ShaderMaterial({
    uniforms: {
      baseTexture: { value: null },
      bloomTexture: { value: null }
    },
    vertexShader: /* vertex shader code */,
    fragmentShader: /* fragment shader code */
  })
);

// Render function
function render() {
  // First render bloom scene to a separate target
  renderer.setRenderTarget(bloomRenderTarget);
  renderer.render(bloomScene, camera);
  
  // Then use composer to apply bloom and composite
  renderer.setRenderTarget(null);
  composer.render();
  
  requestAnimationFrame(render);
}

Important Considerations

1. The bloom effect in Three.js is typically applied using UnrealBloomPass or similar passes within the EffectComposer pipeline.

2. To selectively apply bloom to objects behind glass, you'll need to:

   • Use separate scenes or layers
   • Render the objects that should bloom to a separate render target
   • Apply bloom to that render target
   • Composite the bloomed render target with your main scene

3. The Python and bash examples you provided don't align with Three.js implementation patterns, which uses JavaScript and WebGL.

For more detailed implementation, I recommend exploring the EffectComposer documentation and examples in the Three.js repository, which would provide more specific guidance for your use case.