Render chunks with tilemap Entity generation > 0 are not visible

[rparrett]

AdapterInfo { name: "Apple M1 Max", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
SystemInfo { os: "MacOS 13.4.1 ", kernel: "22.5.0", cpu: "Apple M1 Max", core_count: "10", memory: "64.0 GiB" }

bisected to 7f5113a

I remember noticing this here: #428 (comment) but can't recall if there was a fix that maybe didn't survive a merge or something.

Repro

cargo run --example chunking

Hold thew key. Newly spawned chunks after the initial setup mostly do not display.

[rparrett]

Still not sure what's going on here, but I have a few observations:

• New chunks seem to be spawned, and old chunks despawned, but new chunks do not render (most of the time)
• Same issue is present with the atlas feature.
• Same issue is present after adding FrustumCulling(false).
• The example "works" (all tilemaps are displayed) if you remove the despawning of far-away chunks.
• Same issue is present when using MyMaterial from the custom_shader example with its handle stored in a resource.
• Same issue is present when storing the texture handle in a resource.

[brandon-reinhart]

Not sure if related, but I noticed that my layer 0 in a multi-layer Tiled map won't render if I have some combinations of totally unrelated despawn_recursive's happen prior and when I examine the map the texture handle on that first layer seems borked. I will try and produce a minimal example. It's kind of in that territory of "might be related, but might be something my particular game's code is doing differently." Without any other changes, it worked fine prior to 0.11.

[rparrett]

Another bizarre observation:

Only tilemap entities with a generation of 0 show up. This is reliably reproducible.

[rparrett]

The tilemap entity generation is being dropped and the entity is later reconstructed without it.

I haven't fully untangled this, but this seems very likely to be the problem. Tilemaps that work as expected are the ones that coincidentally have a generation of the default 0.

We can likely use to_bits and from_bits for this sort of thing at the cost of 32 bits.