Heightmap compression with the tradeoff between precision and disk space

[Radivarig]

Description

Heightmap compression sound useful for scaling regions if they are partially painted or with an acceptable loss of precision.
The video also shows a compression method that uses approximation of region subparts by storing them as slopes, which I find quite interesting.

Godot Compression Algorithm for Heightmap Terrain:
https://www.youtube.com/watch?v=5KkVftV-PTk

[TokisanGames]

I moderated my tone a bit above. Thinking more about this, there's nothing in that video that is useful for memory savings, so this is only about disk space. I will rename the title as such.

We can't save more than 80-90 regions anyway, but once #374 is available, we'll be able to save 256 and eventually 2048. And disk space may be a growing issue. Godot already compresses resource files with Zstd, which is ok. We provide an option for lossy 16-bit saving as well. Another option can be useful.

We can explore the video creator's repository.

@SlashScreen Already started an implementation of improved disk compression. What's the status of that?
https://github.com/SlashScreen/hcompress

[SlashScreen]

oh yeah, I stopped working on it since it became clear #374 was more important/would have made compression easier. I still don't know for sure that it's even helpful, anyway.