Serialization of ParametricGeometry, ParametricBufferGeometry contains unserializable function

[jsantell]

Description of the problem

The parametric function in a ParametricBufferGeometry ultimately gets serialized as { func } on the geometry, and since it is a function, the object representation is no longer serializable, at least in terms of the web's structured clone algorithm. In the context of other serialization issues (#17328, #16816, #16764), maybe this issue would be better framed as, "What is the serialization strategy for three.js objects?"

[Mugen87]

"What is the serialization strategy for three.js objects?"

Some classes in three.js were developed without serialization/deserialization in mind. ParametricBufferGeometry is one of these for sure.

I guess we can solve this issue by implementing toJSON() in ParametricGeometry and ParametricBufferGeometry like so:

toJSON() {

    var data = super.toJSON();

    data.func = this.parameters.func.toString();

    return data;

}

Deserializing in ObjectLoader would look like so:

var func = new Function( 'return ' + data.func )();

We consider the parametric functions as self-contained (like ParametricGeometries.klein) so this approach should work.

Better suggestions?

[jsantell]

@Mugen87 that should work if the function contains only local variables and globals (e.g. Math) like you mention; using a pure function is not a requirement of ParametricGeometry, so the unserialization could always fail, but at least serialization is possible. I'll check out a PR for this -- thanks!

[Mugen87]

As mentioned by @mrdoob in the linked PR, the proposed code is not safe enough since malicious code could be injected into 3D scenes.