Implementing Mesh Movement in Three.js with React Three Fiber

Your approach to implementing draggable meshes in Three.js using React Three Fiber is generally sound, but there are some optimizations and best practices you could consider.

Current Implementation Analysis

Your code correctly:

• Uses raycasting to detect intersections with a plane
• Calculates mouse positions relative to the canvas
• Tracks dragging state and position offsets
• Sets up and cleans up event listeners

Suggested Improvements

1. Use React Three Fiber's Built-in Events

React Three Fiber provides built-in event handling that's more React-friendly than manually adding DOM event listeners. This approach is more idiomatic and reduces boilerplate:

TYPESCRIPTCopied
import { useThree } from "@react-three/fiber";
import React, { useRef, useState } from "react";
import * as THREE from "three";

const MovingImage: React.FC<React.PropsWithChildren> = ({ children }) => {
  const { camera } = useThree();
  const [dragging, setDragging] = useState(false);
  const meshRef = useRef<THREE.Mesh>(null);
  const [offset, setOffset] = useState(new THREE.Vector3());
  const plane = new THREE.Plane(new THREE.Vector3(0, 0, 1), 0);
  const planeIntersectPoint = new THREE.Vector3();

  const handlePointerDown = (event) => {
    if (!meshRef.current) return;
    
    event.stopPropagation();
    
    // Create a ray from the camera through the pointer position
    const raycaster = new THREE.Raycaster();
    raycaster.setFromCamera(event.point, camera);
    
    if (raycaster.ray.intersectPlane(plane, planeIntersectPoint)) {
      setDragging(true);
      setOffset(meshRef.current.position.clone().sub(planeIntersectPoint));
    }
  };

  const handlePointerMove = (event) => {
    if (!dragging || !meshRef.current) return;
    
    // Create a ray from the camera through the pointer position
    const raycaster = new THREE.Raycaster();
    raycaster.setFromCamera(event.point, camera);
    
    if (raycaster.ray.intersectPlane(plane, planeIntersectPoint)) {
      const position = planeIntersectPoint.clone().add(offset);
      meshRef.current.position.copy(position);
    }
  };

  const handlePointerUp = () => {
    setDragging(false);
  };

  return (
    <mesh 
      ref={meshRef}
      onPointerDown={handlePointerDown}
      onPointerMove={handlePointerMove}
      onPointerUp={handlePointerUp}
    >
      {children}
    </mesh>
  );
};

export default MovingImage;

2. Consider Using Existing Libraries

For more complex interactions, consider using libraries like @react-three/drei which provides utilities like useDrag that handle much of this logic for you:

TYPESCRIPTCopied
import { useDrag } from "@react-three/drei";
import React, { useRef } from "react";
import * as THREE from "three";

const MovingImage: React.FC<React.PropsWithChildren> = ({ children }) => {
  const meshRef = useRef<THREE.Mesh>(null);
  
  // useDrag handles the dragging logic for you
  const bind = useDrag(({ offset: [x, y] }) => {
    if (meshRef.current) {
      meshRef.current.position.x = x;
      meshRef.current.position.y = y;
    }
  }, { pointerEvents: true, plane: "xy" });

  return <mesh ref={meshRef} {...bind()}>{children}</mesh>;
};

export default MovingImage;

3. Performance Optimizations

• Create reusable objects outside of event handlers to avoid garbage collection
• Consider using useCallback for event handlers to prevent unnecessary re-renders
• Only update the dependency array in useEffect with values that actually change

4. Handling Multiple Objects

If you need to handle multiple draggable objects, consider implementing a more generic solution that can be applied to any mesh.

Conclusion

Your current implementation is a good starting point, but using React Three Fiber's built-in event system or specialized libraries like @react-three/drei can make your code more maintainable and performant. The choice depends on your specific requirements and how much control you need over the dragging behavior.