Use serde for world serialization

[ReCore-sys]

Currently we use bitcode for the serialization, which is fine, but has some issues regarding foreign types. If a type doesn't implement Serialize/Deserialize you can't manually implement it which is very annoying for bevy's math primitives. Wincode does let you define custom serialize/deserialize functions which lets us make serialization method for our Position and Velocity wrappers. Also apparently wincode is faster, but I haven't checked that and it's unlikely to be a bottleneck.

Edit: After some benchmarks and taking into account the serde ecosystem, it ended up being better to just use serde with bitcode. There is a performance drop, but it integrates better with 3rd party libraries.

[alex-s168]

It would be cool to use a more standard format, like CBOR, with for example minicbor

[ReCore-sys]

Possibly, but I'd want to be able to define custom ser/de implementations and idk if cbor would support that.

[alex-s168]

yes minicbor supports that

[ReCore-sys]

In that case im happy to give it a shot

[ReCore-sys]

@alex-s168 so i did some benchmarks recently, cbor type serialization systems seem to perform pretty poorly. They all seem to have fairly poor performance and the output isn't very small after compression. I don't know if it'd be a good idea to use a cbor system simply for compatibility with other tools.

[ReCore-sys]

after comparing a bunch of crates (though not wincode cos i forgot) i made this graph plotting round trip encodes/decode + compress/decompress against the size of the compressed output and the cbor-style crates didn't do all that well. In the graph wincode is the unreadable pale yellow dot so it also didn't do great on performance, only compressibility. Postcard seems to be the best option in terms of speed and has decent size, and it runs on serde so i'm leaning towards that one.

[ReCore-sys]

postcard is a rust-specific crate, not a well-known format like cbor, but it does have a well documented format here so external tools could replicate it.