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Special advise and little known facts

Special advise and little known facts   [ edit page ]



General

  • Lua scripts run on the server and on the client, they can get into a state where they are not syncronized (e.g. math.random())! While the composite input and output are syncronized, the output on the screen can be different!
  • When vehicle are out of sight (too far away) they despawn. Once you are coming closer, the spawn again. The values of Memory components is being restored, but the lua scripts are reset (like on spawn from workbench). If you need to persist some data, use Memory components or use a No-Despawn-Block (NOT RECOMMENDED because of performance problems!).

Interacting with composite data / onTick

  • the function is called everytime the physics engine calculates a new tick. The frequency is ~60 times per second, but can be way less when you spawn in large vehicles or are in multiplayer
  • you are not allowed to access screen functions at this time, this needs to be done in onDraw()
  • if the execution of onTick() takes longer than 16ms, you effectively slow down the physics engine speed of the game (= slow down)
  • if the execution of onTick() takes longer than 100ms, the game will exit the function and discard the calculations done


Interacting with the Screen / onDraw

  • the function is called everytime the game draws a new frame. The frequency depends on your games FPS and is either ~60 times per second (no vsync) or ~30 FPS (with vsync)
  • you are not allowed to access composite input and output at this time, this needs to be done in onTick()
  • for every connected monitor, this function will be called once. If you have 5 monitors connected, the function will be called 5 times per frame.
  • if you the position of stuff to draw on the monitor is based on its size (e.g. screen.getWidth()/2) the stuff will look different on monitors with different sizes, but connected to the same script
  • if the execution of onDraw() takes longer than 16ms, you effectively slow down the FPS of the game
  • if the execution of onDraw() takes longer than 100ms, the game will exit the function and discard the drawn stuff

Special Cases

BUS / synchronized and fast changing data (every tick different data)

The problem is: every logic component needs 1 tick to process data. When you programatically send data over composite, you will send different values every tick, to maximize bandwidth. While you are sending from one script to another script, this is no problem, but when the receiver is not a script you get into trouble.

Imagine following example:
You have a Bus system which sends data to receivers, one after another. The number channel 1 will contain the ID of the receiver, the other channels contain the data. Now the receiver only reads the data if the id on number channel 1 equals his own id. This procedure needs 2 ticks to process: 1 tick for composite read and 1 tick for the equal check. The output of the equal check will now control a composite switchbox that either forwards the composite data to whatever reads the data, or it discards it (in case the ID is not equal to my ID). But the time for the composite to travel to the composite switchbox is only 1 tick, while the time for the boolean to travel to the switchbox is (like we calculated before) 2 ticks.
This means: we forward the wrong data! We forward the data which was sent 1 tick before our ID matched number channel 1!

Solution: artifically increase the tick time for the composite. We simply add another composite switchbox, inbetween the original composite and the boolean controlled switchbox. This has no effect on the composite (because we connect it to the OFF position) but only delays the composite by 1 tick. In the end the composite data needs the same time the equal check needs.

onDraw while game is paused

Even if the game is paused, onDraw() is being called. onTick() is not being called. This can lead to unexpected behaviour.

FPS and TPS (Ticks per second)

If the TPS, the physical ticks, slow down, the FPS of the screens and also the frequency of onDraw() calls will slow down!

Nonstandard LUA API

math.atan2

In Stormworks, math.atan2 does not exist. Note that math.atan2 normally requires two arguments in Lua, while math.atan only requires one. , In Stormworks, math.atan can take either one or two arguments, so it can also be used as if it were math.atan2.

table.maxn

Stormworks implements many of Lua's table functions, but maxn is not implemented.


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