The old X^2 + Y^2 + Z^2 formula is always the way to go. The sines and cosines you mentioned before are nessasary to set the three co-ordinates to begin with. Once you have those coordinates set (in stone, so to speak) then your game is ready to go. I have seen grid maps of 3D games before, and enjoyed some, and the designer always goes thru the trouble and work setting up these X,Y,Z things before hand. The formula is only for determining the straght line distance a ship must travel.
BTW, I have done it myself in years gone by, and getting those coordinates set is A LOT OF WORK. So, don't envy my failer to finish the project. Getting the real time positions of the stars is a bunch more than I ever did. More power to you.
Sure, Life IS like a bowl of cherries, but how SWEET they are depends on how much crap your willing to take to fertalize your DREAMS. Michael L. Cross