Main Page » Weapon Scripts

Revision as of 23:38, 21 February 2009

Weapon Scripts

Introduction

Scorched3D supports configurable weapons via its XML accessory definition files, see current scorched3d weapons. The XML definitions allow you to make an almost limitless number of complex weapons, and in most cases this is the easiest way to create new weapons.

In some cases the XML accessory definition files don't allow you to create the weapons you want, perhaps the weapons are very complex or the XML syntax doesn't exist. For these occasions you can Weapon Scripts.

Instead of XML Weapon scripts use the LUA scripting language to define Scorched3D weapons. See Scorched3D scripting home for an introduction to scripting on Scorched3D.

LUA

Weapon scripts are written as normal text files containing LUA code. See LUA Documentation for documentation on the LUA scripting language.

The LUA interpreter imbeded in Scorched3D supports the following standard libraries-

Basic functions

String manipulation

Table manipulation

Mathematical functions

Scorched3D specific functions

All of the standard libraries are documented in the LUA Documentation, with the exception of the Scorched3D functions. The Scorched3D functions allow scripts to interact with and manipulate the Scorched3D engine.

Weapon Scripts

Entry Point

Weapon scripts are just normal LUA scripts. However there must be one function (the entry point) in the LUA script that takes a playerId, a position and a velocity. Simply put, one function in the script must look like this:-

  function runWeapon(playerId, position, velocity)

This is the function that will be called when ever this weapon is executed. You can have as many other functions as you need in the file but this one is mandatory.

The three arguments to this function are as follows-

playerId - An integer id of the player that fired this weapon

position - A table containing the coordinates of the current weapon

velocity - A table containing the velocity factors for the current weapon

Simple Example Script

Here is a very simple weapon script:

 function runWeapon(playerId, position, velocity)
   print(playerId);
   print(position.x, position.y, position.z);
   print(velocity.x, velocity.y, velocity.z);
 end

As you can see it implements the runWeapon function. When executed the script will print the playerId, position and velocity to the Scorched3D console. You can access the console by pressing the ` key.

Using the Scorched3D functions

What makes the Scorched3D scripts useful is using them to interact with the Scorched3D engine. To do this Scorched3D provides a set of library functions that be called from within your scripts.

Currently scorched3d provides two libraries-

s3d - The base scorched library containing generic scorched3d functions. See LUA s3d library

s3dweapon - The scorched3d weapons library containing functions specific to creating and manipulating weapons. See LUA s3dweapon library

For example, the following script prints the size of the current landscape to the console:

 function runWeapon(playerId, position, velocity)
   landwidth = s3d.get_landscapewidth();
   landheight = s3d.get_landscapeheight();
   print("Landwidth", landwidth, "Landheight", landheight);
 end

This script uses the s3d.get_landscapewidth and s3d.get_landscapeheight functions that are defined in the s3d library.

Example 1

You can combine Scorched3D functions with the LUA functions to perform very complicated operations. For example, the following script creates a set of explosions in a diagonal line across the landscape.

 function runWeapon(playerId, position, velocity)
   -- Get the landscape width and height using the s3d library functions
   landwidth = s3d.get_landscapewidth();
   landheight = s3d.get_landscapeheight();

   -- Print the width and height to the console
   print("Landwidth", landwidth, "Landheight", landheight);

   -- Create an explosion line from landscape corner to corner
   landstart = 0;
   while (landstart < landwidth and landstart < landheight) do
      -- Get the current landscape height at the position landstart, landstart
      height = s3d.get_height(landstart, landstart);

      -- Use the s3dweapon.explosion function to make an explosion
      s3dweapon.explosion(
        playerId, -- Create an explosion for the same player as fired this weapon
        {  -- Create a table that has the position of the explosion
            x=landstart, 
            y=landstart, 
            z=height 
        }, 
        { -- Create a table that describes the explosion parameters
            size = 4,  -- The size of the explosion
            hurtamount = 0,
            deform = 2,
            animate = false
        }); 

        -- Move to the next position	
        landstart = landstart + 15;
     end
  end

Example 2

The following example creates an explosion 10 units to the right of the player that fired the weapon.

 function runWeapon(playerId, position, velocity)
   s3dweapon.explosion(
     playerId, -- Create an explosion for the same player as fired this weapon
     {  -- Create a table that has the position of the explosion
         x=position.x + 10, 
         y=position.y, 
         z=position.z 
     }, 
     { -- Create a table that describes the explosion parameters
         size = 4,  -- The size of the explosion
         hurtamount = 0,
         deform = 2,
         animate = false
     }); 
 end

Example 3

This example finds all tanks that are currently playing and fires a "Nuke" weapon at their positions.

 function runWeapon(playerId, position, velocity)
   -- Get a table containing all of the tanks currently playing,
   -- the table key is the playerid
   -- the table value is the tank details
   tanks = s3d.get_tanks();

   -- Iterate over these tanks, k is the playerid, v is the tank details
   for k,v in pairs(tanks) do 
     -- Check the tank is still alive
     if (v.alive) then 
       -- Fire a nuke at this tanks position using the s3d.fireweapon function
       s3d.fire_weapon(
          "Nuke",  -- Fire a "Nuke" weapon
          playerId,  -- From the same player that executed this script
          v.position,  -- At the tanks location
         {x=0, y=0, z=0} -- With no speed or direction (velocity)
        );
     end -- End if
   end -- End for
 end -- End function

Weapon Script Pitfalls

Printing

Using the print function can be a simple way of debugging scripts, however print statements slow down the game and should not be present in the final version of the script.

Performance

Scripts give you much power, but with that comes great responsibility! While the engine is optimized, performing huge amounts of calculations in a script or firing a large number of weapons/explosions will slow the game down. Don't go overboard with the amount of work you try to do in a script.

You can used the ActionProfiling console command to check how many explosions and actions were fired in a turn. After each turn the number of actions should be printed to the console.

 ActionProfiling = on 

Global variables

It's fine to use global variables but don't use them to store data across different runs of the same script. Put another way just asume the script will be started from fresh every time.

Storing data for use across different executions of the same script will cause online games to become out of sync and ultimately fail.

WeaponScript AccessoryAction

In fact the configuration for the Weapon Scripts is in the existing XML file (accessories.xml), but this is purely used to tell Scorched where to find the script and when to use it. Weapon scripts are defined in new type of accessoryaction called WeaponScript. This WeaponScript is just a 'normal' accessoryaction and can be used interchangably with other accessoryactions in the accessories.xml.

Here is an example WeaponScript accessory action:

 <accessoryaction type="WeaponScript">
   <filename>data/lua/accessories/test.lua</filename> 
   <entrypoint>runWeapon</entrypoint> 
   <variable>
     <name>testvar1</name> 
     <value>10</value> 
   </variable>
 </accessoryaction>

The above accessoryaction has two mandatory parts, the filename and the entrypoint:

• filename is the path to the LUA script that you want to run when the accessoryaction is executed.
• entrypoint is the LUA function in the script to execute when the accessoryaction is executed.
• variable is a *optional* list of variables that may be passed into the script.

Here is an example use of a WeaponScript:

 <accessory>
   <name>Test Script</name> 
   <bundlesize>2</bundlesize> 
   <cost>10</cost> 
   <accessoryaction type="WeaponScript">
     <filename>data/lua/accessories/test.lua</filename> 
     <entrypoint>runWeapon</entrypoint> 
   </accessoryaction>
 </accessory>

The above accessory creates a weapon called 'Test Script'. When the tank fires this weapon the runWeapon function in the data/lua/accessories/test.lua script will be executed.

Obviously this is a very simple example and as stated earlier you can use WeaponScripts anywhere that you can use an accessoryaction.

Weapon Scripts Walkthrough

Here is the basic steps you should use to create a weapon script:-

1. Write the weapon script and save it to a text file.
2. Put this text file into your mod. Generally under the data/lua directory.
3. Edit the accessories.xml file and create/add your new weapon. This weapon should contain a call to a WeaponScript accessorypart somewhere within it.
4. Run Scorched3D
5. Choose a custom game using your mod and test your new weapon
6. Rejoice