bug: follow cam doesn't register objects newly added or removed from scene

replace the code below in the example

I added a test that toggles the Slopes every 3s and you can see that the camera still detects slopes and zooms in even though the slopes have been removed from the scene

the problem is that the useFollowCam relies on component render, so if you add or remove elements that aren't at the level ecctrl was invoked then it won't rerender ecctrl and useFollowCam wouldn't update the intersectObjects array

import { RigidBody } from "@react-three/rapier";
import { useGLTF, Text } from "@react-three/drei";
import { useEffect, useState } from "react";
import * as THREE from "three";

export default function Slopes() {
  // Load models
  const slopes = useGLTF("./slopes.glb");
  const [visible, setVisible] = useState(true);
  useEffect(() => {
    // Receive Shadows
    slopes.scene.traverse((child) => {
      if (
        child instanceof THREE.Mesh &&
        child.material instanceof THREE.MeshStandardMaterial
      ) {
        child.receiveShadow = true;
      }
    });
  }, []);

  useEffect(() => {
    const a = setInterval(() => {
      setVisible(!visible);
    }, 3000);

    return () => {
      clearInterval(a);
    };
  }, [visible]);

  if (!visible) {
    return null;
  }

  return (
    <group position={[-10, -1, 10]}>
      <RigidBody type="fixed" colliders="trimesh" rotation={[0, Math.PI, 0]}>
        <primitive object={slopes.scene} />
      </RigidBody>
      <Text
        rotation={[0, Math.PI, 0]}
        position={[3.5, 3, 0]}
        color="black"
        fontSize={0.5}
      >
        23.5 Deg
      </Text>
      <Text
        rotation={[0, Math.PI, 0]}
        position={[0, 4.5, 0]}
        color="black"
        fontSize={0.5}
      >
        43.1 Deg
      </Text>
      <Text
        rotation={[0, Math.PI, 0]}
        position={[-3.5, 7, 0]}
        color="black"
        fontSize={0.5}
      >
        62.7 Deg
      </Text>
    </group>
  );
}

https://github.com/user-attachments/assets/ade3537f-51dd-4c98-bd67-7e4f49e78980

Start in the example and the useFollowCam implementation; reproduce the Slopes component toggling every 3 seconds and inspect how intersectObjects is updated when nested objects mount or unmount. Done means the follow camera detects newly added slopes and stops detecting slopes after they are removed from the scene.