Arma 3 Scripting

Mission Optimisation

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Note

This page is about Mission Optimisation. For scripting optimisation, see Code Optimisation.

This article will try to be a general guide about improving your mission's performance.
As usual, moderation is the key; do not expect to find on this page a magical solution that makes it possible to run thousands of AI at 240 FPS. Everything comes at a cost, the tweaks here will simply allow you to locate issues and calibrate your mission properly.

Before Anything

Before optimising anything, make sure you do not have any performance issue running the game itself:

Important

Please note that view distance (among other settings) impacts both GPU and CPU!

Note

View distance can be separately set for each clients independently from the server's value through scripting.
This can make or break performance for the client.

Mission Creation

Performance Impact Table

Note

● means a heavy impact on performance ● means an average impact ● means little to no performance impact.

Topic CPU GPU Net-
work		 Solution
AI unit quantity ● ● ● - Use Agents whenever possible
- The more units there are, the more network updates there will be - hence the impact on both CPU and network.
- If a client has a low-end machine, they should not lead a group of many AIs as these would then be locally computed.
- Arma 3: Dynamic Simulation allows you to freeze AI that are distant from players. Many distance settings should be set according to the mission.

Note

If you own more than one average computer, you could consider Headless client to offload AI from the server.
Object quantity ● ● ● The less objects, the more FPS you will have.
- Lower the quantity of objects in the mission, such as:
- AI units, agents
- vehicles, simple objects
- weapon attachments (their proxies are attachedTo)
- headgear, clothing, vests, backpacks
- head-mounted devices (NVGs, etc.)
- Lower view distance
- Lower terrain details
- Lower the Dynamic Simulation threshold
- Use Simple Objects
- Use Garbage Collection in order to automatically delete bodies and wreckages:
- Arma 3's Eden-integrated Garbage Collection
- Arma 2's Garbage Collector
- Take On Helicopters's BIS_fnc_GC

Note

Only the on-screen objects will strongly impact the GPU.
General script mistakes ● ● ● Having too many scripts running is a cause for severe performance issues and execution delays in singleplayer as well as multiplayer.
- You can track the number of running scripts using diag_activeScripts; you can also use:
- diag_activeSQFScripts
- diag_activeSQSScripts
- diag_activeMissionFSMs
- A common bad practice is to spawn a function for each units that need it; the good practice would be to have a single script working with an array of units, array that is edited (unit added/removed) whenever needed:
  { _x spawn _myCode; } forEach _units;    // bad
  _units spawn _myCode;                    // good

You can use diag_activeSQFScripts to ensure you are not clogging your CPU with multiple instances of the same script.
- Not compiling your scripts: running multiple times the same script with execVM will make the game read the file every single time; This is an issue, especially if you execute it frequently.
  while { sleep 5; alive player } do { player execVM "myScript.sqf"; };    // bad
  private _myScript = compile preprocessFileLineNumbers "myScript.sqf";
  while { sleep 5; alive player } do { player spawn _myScript; };            // better
  while { sleep 5; alive player } do { player spawn TAG_fnc_myScript; };    // perfect! see Functions
High-frequency scripts ● ● ● Checking a condition too often is usually a source of poor performance. Does your code execution need to be frame-perfect, or can you afford a delay of a few seconds?
- A while-loop checking without a minimum loop-sleep time is usually a sign of bad conception.
  while { true }                        // bad if you do not know what you are doing
  while { alive player }                // better
  while { sleep 1 ; alive player }    // perfect

- By default, Triggers check their set condition every 0.5 second. If a large area is covered or condition code is too complex, this can become an issue; the triggers should then be converted to scripts if possible. Since Arma 3 v2.00 it is possible to change trigger intervals, either via trigger attributes in 3DEN, or via the scripting command setTriggerInterval.
- Triggers can be made Server-Side only to save clients' resources.

Important

All of the mission-related calculation (objectives, completion distance, etc.) must be done server-side. Local effects should be calculated client-side.
High-frequency network messages ● ● ● - Use publicVariable wisely; for specific cases, consider publicVariableServer / publicVariableClient
- Creating units/vehicles globally implies a network synchronisation, keep them to a minimum / at one-point in the mission.
- Keep global effect commands to a minimum:
- e.g a setPos will synchronise the unit position to every client, a good practice is to use these commands punctually. If you need a frequent "set position" you may want to look at attachTo depending on your usage.
- global marker commands always send all the marker's information. If you are creating/updating many markers e.g server-side, edit them with local commands, except the last one (that will be global) to send the whole marker's status over the network, once.
- Lower client's view distance in order to lessen its object position update requests
Unscheduled code ● ● ● Unscheduled code can have a high impact on the framerate, as such code is not subject to the scheduler's management (as its name suggests) and will run without limitation. Cyclic unscheduled low-performance code can make the game unplayable, up to freezing it.
- As only time-critical scripts should run unscheduled, spawn any other code from unscheduled environment once you have the required results:
  /* ... */ // unscheduled code
  [_var1, _var2] spawn TAG_fnc_MyFunction;
  /* ... */ // other unscheduled code

Note

See also Scheduler - Where code starts unscheduled.

What Else?

If you have applied all these recommendations and your mission still does not run well in multiplayer (but does in singleplayer), it might be caused by mods that you are running which could be badly, or not at all, optimised.

If you want to be sure, run the same mission with and without mods. If you have a big difference in performance, look no further.

Performance Diagnostic Tools

Server Commands

Diagnostic Commands

See Also