@react-three/fiber: How do I create a helper for a shadow camera?

Question

So I am used to setting helpers like this:

useHelper(sLightRef, THREE.SpotLightHelper);

return (
    <spotLight
        castShadow
        ref={sLightRef}
        position={[0, 2, 2]}
        args={["#fff", 0.4, 10, Math.PI * 0.3]}
    >
    </spotLight>
)

Which will create a helper on the SpotLight object.

What I don't understand is how to create one on the SpotLight's shadow camera. (spotlight.shadow.camera) We can't assign a ref() to it, since it's not in my return statement. It's created inside of SpotLight component.

In normal Three.js, this is easy:

const helper = new THREE.CameraHelper(spotlight.shadow.camera);
scene.add(helper);

How would I go about doing this in react-three-fiber? Is there something obvious i'm missing? Thank you.

Answer 1

I played around with it a bit but I couldn't find a clean solution. That's why I made my own hook that's built similarly to the useHelper hook.

// Components==============
import { useFrame, useThree } from '@react-three/fiber';
import React, { useRef } from 'react';
import { CameraHelper, Light } from 'three';
// =========================

export default function useShadowHelper(
    ref: React.MutableRefObject<Light | undefined>
) {
    const helper = useRef < CameraHelper > ();
    const scene = useThree((state) => state.scene);

    React.useEffect(() => {
        if (!ref.current) return;

        helper.current = new CameraHelper(ref.current?.shadow.camera);
        if (helper.current) {
            scene.add(helper.current);
        }

        return () => {
            if (helper.current) {
                scene.remove(helper.current);
            }
        };
    }, [helper.current?.uuid, ref.current]);

    useFrame(() => {
        if (helper.current?.update) {
            helper.current.update();
        }
    });
}