Planet XYZ Distance Limits

[WAS]

I'm just curious, and it's a little hard to tell on an actual planet (least tests I was doing).

If a planet radius is 6378000, what is maximum distance in any direction on X Y Z in pos/neg?

Ya all know I'm terrible at math. Is the limit 6378000? I tried some 3d coordinate systems from 0,0,0 to 6378000 and it gave me 11047020.050674 as a distance. I'm sure that's shortest route through the planet.  Lol I'm just confused.

[Dune]

It's double the radius; the diameter. Unless there's mountains on either side

[WAS]

Sweet, thank you. I wonder how it translates because for my crater generate the planet radius seems to do global craters when using it as a negative / positive limit.