when I was still playing with the map I was working on.... I had a bitmap that was like 17,000x19,000 or something.. I forget what it ended as after the hex, and +1 and everything...
it was like 22x24 .... but it had issues rendering properlly cause of the rectangle, so I made it square at 24x24 and it worked....
don't be discouraged ... yet.....
though I'd reccomend using FEATURES for the ships, rather than the map....
I could model some, but texturing a ship takes aLOT more time than "spray painting" a rock in Deep Paint 3D...
but it can be done....
I have lots of projects right now though.... maybe you can look online for usable ship models? look around the FREELANCER mods... they have LOTS of ship models available to the public..
