get_bone_position does not return default bone position

[appgurueu]

Minetest version: 5.1.1

Summary

Using (minimal example):

minetest.register_globalstep(function()
    for _, player in pairs(minetest.get_connected_players()) do
        local position, rotation = player:get_bone_position("Head")
        player:set_bone_position("Head", position, rotation)
    end
end)

in a mod causes the player to look like this:

As position (and rotation) are {x = 0, y = 0, z = 0}, which they obviously shouldn't be.

[appgurueu]

I have investigated and found the root cause. get_bone_position only returns values previously set with set_bone_position; it does not know about the models default bone positions at all.

[appgurueu]

The server doesn't really know about models so this can hardly be fixed there; having the client send bone positions would be odd (especially accounting for lag and animations). Mod workarounds exist (see modlib's B3D reader & character_anim's use of it). The proper way to solve the "underlying" issue is #10704.