What’s Lua?• Scripting language• Works through LVM (Lua Virtual Machine)• Stack model design• “Ultimate game scripting language” (GDC 2010)• Popular uses in games• Runs on most machines and devices• Written in ANSI C and distributed by small library
Lua Benefits• Free and open source • Support OOP• Runs on almost platforms• Easy to interface with C/C++• Very clean C API• Auto memory management (GC)• Powerful, fast and lightweight• Flexible data structure (TABLE)
Lua Benefits• Contents can be changed in real-time• Auto generate contents• Users can customize/change contents• Fast and easy distributed contents• Secure code• Easy to use, embed and learn• Good references
• Lua APIs – Call to LVM through events/triggers base – C APIs to work with LVM – Auxiliary library provides basic functions to check, register, debug, … LVM – Use C APIs to build core functions• Lua Interface – Call to core logic through exports APIs – Provides APIs (game APIs) to work with core logic – Use C APIs to build, register, and exports APIs
Quick Samplefunction OnPlayerUseItem(nItem) core.InstanceObj(OBJ_KIND_ITEM, nItem) if item.GetKind() == ITM_KIND_HP then local nItemHP = item.GetAttribute(ITM_ATTR_HP) local nPlayerHP = player.GetCurrentHP() local nAddHP = 0.2 * nPlayerHP if nAddHP > 0 and nAddHP < player.GetMaxHP() then player.SetCurrentHP(nAddHP) player.Message(Player:..player.GetName().. use item ..item.GetName()) end endend
• C APIs are too low-level• Error messages are very confusing • No try-catch, no exceptions• Hard to debug• Hard to interfaces with unlike C/C++• Once LVM is crashed, it’s not likely to recover and the service is crashed too • Hard to implement reload feature at run-time• For extreme speed, LuaJIT is a good choice
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