Creating Interactive Overlays in Three.js

Based on the information available, there are several approaches you could use to create an overlay effect in a Three.js/React Three Fiber application. While your question mentions React Three Fiber specifically (which is not directly covered in the provided context), I can suggest some Three.js techniques that would work in that environment.

Recommended Approaches

1. Using CSS2DRenderer or CSS3DRenderer

Three.js provides specialized renderers that can help with creating HTML overlays on top of your 3D scene:

• CSS2DRenderer: Good for simple 2D HTML elements positioned in 3D space
• CSS3DRenderer: Allows for more complex HTML elements with 3D transformations

These renderers allow you to attach HTML elements to specific 3D positions, which would be perfect for creating interactive overlays that appear when clicking on specific areas.

2. Using WebGLRenderer with Custom Shaders

If you need the overlay to be part of the 3D scene itself (rather than HTML):

• Create a transparent material with custom shaders
• Apply this material to a plane or mesh that covers your target area
• Toggle the opacity or visibility of this overlay mesh on button click

3. Using Controls for Interaction

You could leverage one of the control systems to help manage the interaction:

• TransformControls: To highlight and manipulate selected objects
• DragControls: If you want users to be able to drag elements

Implementation Example

Here's a simplified example of how you might implement the CSS2DRenderer approach in React Three Fiber:

JSXCopied
import React, { useRef } from 'react'
import { Canvas, useFrame, extend, useThree } from '@react-three/fiber'
import { CSS2DRenderer, CSS2DObject } from 'three/examples/jsm/renderers/CSS2DRenderer'

// Make CSS2DRenderer available in React Three Fiber
extend({ CSS2DRenderer })

function Overlay({ position, visible, content }) {
  // This component represents your overlay
  return visible ? (
    <CSS2DObject position={position}>
      <div className="annotation">
        {content}
      </div>
    </CSS2DObject>
  ) : null
}

function Scene() {
  const [selectedArea, setSelectedArea] = useState(null)
  
  const handleClick = (areaId) => {
    setSelectedArea(areaId === selectedArea ? null : areaId)
  }
  
  return (
    <>
      {/* Your 3D objects */}
      <mesh 
        onClick={() => handleClick('area1')} 
        position={[0, 0, 0]}
      >
        <boxGeometry />
        <meshStandardMaterial />
      </mesh>
      
      {/* Overlay that appears when area is selected */}
      <Overlay 
        position={[0, 1, 0]} 
        visible={selectedArea === 'area1'}
        content={<div>Area Information</div>}
      />
    </>
  )
}

This approach is generally more efficient than creating and hiding complete duplicate models, as you're only adding lightweight overlay elements when needed.