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== Overview of differences between COB unit scripts and Lua unit scripts ==
This is only of interest if you plan to port your COB scripts to Lua:
* Units of measurement: Lua uses elmos and radians consistently.
* Coordinate system: In Lua, coordinate system is same as world coordinate system, with all rotations right-handed. In COB, the moves along the x-axis and rotations around the z-axis have a different sign.
* In Lua, ''Killed'' gets recentDamage and maxHealth as separate arguments. In COB, you get only the ratio recentDamage/maxHealth*100.
* Where COB uses ''SetMaxReloadTime'', Lua uses ''GetMaxReloadTime''.
* Where COB uses ''QueryLandingPadCount'' and ''QueryLandingPad'', Lua uses ''QueryLandingPad'''s'''''
* The x and z arguments to ''HitByWeapon'', ''HitByWeaponId'' and ''RockUnit'' are given in (x, z) order in Lua, and the opposite order in COB.
* ''BeginTransport'' and ''EndTransport'' take the height of the unit in COB and the unitID in Lua. (Use 'local height = Spring.GetUnitHeight(unitID)' to get the height.)
* ''TransportDrop'' gets PACKXZ(x,z) in COB; in Lua, it gets the entire vector (x, y, z) as three arguments.
* Where COB uses ''SetSpeed'' and ''SetDirection'', Lua uses ''WindChanged'' and ''ExtractionRateChanged''.
* Lua does not have ''Go'' (this is called for activated extractors immediately after each ''SetSpeed'' call.)

==Which one is better? Lua or COB unitscripts?==
If you are starting a new project and wonder what script language to use, look at this list: 
'''data types:''' 
COB: - only basic variables. 
Lua: + arrays, strings and tables. 
This is quite important as it allows for easier creation of advanced scripts. 

'''availability of examples, documentation''' 
COB: + is/was used in Total Annihilation. Lots of third party units were made for that game and maybe you can reuse some scripts. 
COB: - unclear legal status of these scripts 
COB: - Outside of the TA community, there are no tutorials and it is unknown. 
Lua: + is also used in projects outside Spring, so it has more tutorials. 
Lua: + The documentation on Spring specific Lua will probably get better, COB not. 

'''Interaction with the rest of Spring''' 
COB: - Typically only basic stuff, but there is a messy way of interacting with gadgets which must be written in a way to support COB interaction. 
Lua: + can use all the other Lua functions Spring has to offer. 
Lua: + game logic (gadgets) is written in Lua, too. So you need to know Lua anyway.

'''Ease of use''' 
COB: - Requires recompiling the script with a compiler after each change. 
COB: - This compiler appears to be pretty buggy. 
COB: - Compiled scripts are not readable for human eyes, but can be decompiled. 
Lua: + A text editor is all you need. Many editors support Lua syntax highlighting. 
Lua: + Scripts are not compiled so it is easy to look at the scripts of other games for examples. 

'''Script performance''' 
COB: + Faster for simple scripts that have no interaction with gadgets. 
COB: - Slower when interacting with gadgets, trickier to code such interaction. 
Lua: - Slower threading engine. 
Lua: + Faster when interacting with gadgets. 

===Conclusion===
Unless you already have lots of complex unit scripts by porting TA content, Lua is always better. 
Contra to popular belief, COB is actually not easier to learn.

==Hints==
* COB & LUS (LuaUnitScripts) can be reloaded ingame via <code>/reloadcob %unitdefname</code>, also LUS get reloaded with <code>/luarules reload</code>, too.

==Avoid writting "COB-style" Lua scripts==
See [http://springrts.com/phpbb/viewtopic.php?f=23&t=25960 this thread] for an example on how you can improve your copy&paste hackjob script.

[[Category:Animation]]

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