Add overload from the docs to MeshBVHHelper type

[pailhead]

I was trying to construct a MeshBVHHelper via a MeshBVH that i constructed via BufferGeometry not a Mesh. The type doesn't support the overload thats listed in the docs.

constructor(
	mesh = null : THREE.Mesh,
	bvh = null : MeshBVH,
	depth = 10 : Number
)

With this change, i seem to be able to pass these three arguments without TS complaining and i see the results. I'm also confused with the default parameters of null since the type doesnt seem to be nullable. This makes it sound like its mesh?: THREE.Mesh | null.

However, if i try to construct this with MeshBVH instead of THREE.Mesh

constructor(
	meshOrBvh: THREE.Mesh | MeshBVH,
	depth = 10 : Number
)

I run into an issue here:

Because of this i believe:

three-mesh-bvh/src/objects/MeshBVHHelper.js

Line 239 in 8f642cb

mesh = null;

If you provide MeshBVH instead, it will set this.mesh = null and then accessing a property on it fails.

I couldn't dig deeper into this at this point. The quickest thing may be to remove the Mesh|BVHMesh from the first argument in that signature and update the docs accordingly.

[gkjohnson]

Hey! Thanks for the catch - this looks like bug introduced in #703 since this line is not checking whether or not mesh is defined. The constructor signatures in the README should be correct.

Can we:

• Add a check for whether or not mesh is defined in the above condition, and
• Adjust the typescript definitions to align with the ones specified in the README

Thanks again!

[pailhead]

Makes sense. If it isn’t super urgent I could address this in a couple of weeks. I erm, just lost access to a computer.