Add a page on large world coordinates (double-precision floats)

[Calinou]

Note: This currently doesn't include the SCons option rename from godotengine/godot#67399.

[mhilbrunner]

Great content! Could maybe mention the shifting-world-origin alternative approach that many games use, as thats a common workaround.

[Calinou]

I mentioned origin shifting in passing, but I don't know how to implement it. It can quickly get complicated (especially for multiplayer games), so it's mainly good to know for low-end mobile.

I added a paragraph on resource saving and interoperability as well. I have some questions:

• Is there a GDScript method or feature tag to check whether the build is using double-precision? For instance, this could be used by plugin authors to warn if the current build isn't using double-precision.
• Does GDExtension have REAL_T_IS_DOUBLE defined when building an extension with float=64, and can you use real_t in extensions? I mentioned this in the docs, but I'm not sure if it's correct.

[mhilbrunner]

I mentioned origin shifting in passing

D'oh, yeah, thats enough already :)

I don't know how to implement it

Roughly: whenever player distance to origin exceeds the shift treshold, calculate the difference between player position and origin and shift everything's position in the game by that difference, so the player is at the origin again, but everything else is still at the same position relative to each other.

Then, pile lots of bandaids and fixes on top as you run into different bugs and edge cases :P

Those additional questions are good ones, no idea honestly, may try out the GDExtension thing. Regardless, I'll go ahead and merge this one now, and we can amend and iterate as needed if we figure out more :) Amazing work, as usual! 🎉