Tutorial - Basic Scripting

As scripting seems to be something difficult for most people to even start utilizing i thought it might be a good idea to write a short tutorial about the issue. Basic understanding of Lua or practically any other scripting or coding language is helpful but is not actually required as there is an abundance of well written guides to scripting in the internet. Some of these have been gathered to the links section in the Scripting.tbl page. Especially the Tutorial Directory in Lua-Users wiki is very usefull in learning to use Lua scripting with FreeSpace Open.

Very Basics

First take a good look at the Scripting.tbl page. From there you can see the hooks you can use for scripting. In addition to these there are few additional in Weapons.tbl, namely $Collide Ship: and $Collide Weapon: but these arent supported by the 3.6.9 code branch.

All the hooks require square brackets after them into where the actual script is inserted.

Scripting.tbl

$Simulation:

[
...
]

Commenting rest of the line away is done with double dashes, like so – –.

First Example

Lets start with creating a small script that writes text to the screen. That is the very old Hello, World example. To achieve that effect we first need to create a scripting.tbl file and then also to create the needed sections. In order to achieve that goal first create a plain text document using (for example) notepad or similar non-formatting text editor.

• Name the empty text file as scripting.tbl
• Move it to data/tables directory
• Add the needed #Global Hooks and #End to the table.

Scripting.tbl

#Global Hooks

#End

Draw Text to Screen

To write text (or rather a text string) to the screen we need to use certain Lua functions. The needed function drawString() is located in the Graphics library (abbreviated gr), Graphic library in Scripting.html. To use that function we first need to create a $HUD: hook where we can place it. The function also needs some arguments and we ought to give it the required arguments. First we need the string 'Hello, World' followed by the location coordinates (pixels) where the game is instructed to draw the string. Also note that as the function is from the Graphics library we need to add gr. before the function (that is to write gr.drawString instead of just drawString).

Scripting.tbl

#Global Hooks

$HUD:

[

--Draws 'Hello, World' to the HUD
gr.drawString('Hello, World', 100, 100)

]

#End

Drawing in Different Locations

In the first example we draw the string so that it started from the position 100, 100. Now lets draw the same string also elsewhere on the screen.

Scripting.tbl

#Global Hooks

$HUD:

[

gr.drawString('Hello, World', 100, 100)
gr.drawString('Hello, World', 130, 160)
gr.drawString('Hello, World', 160, 220)
gr.drawString('Hello, World', 190, 280)

]

#End

Drawing in Different Colors

Now that we have several text strings drawn to the screen we might want to try to alter their colors. For this we need another function from the Graphics library, setColor() that accepts four arguments. These are basic RGBA values of which the A (alpha or transparency) is optional.

Scripting.tbl

#Global Hooks

$HUD:

[

gr.setColor(0, 255, 0)
gr.drawString('Hello, World', 100, 100)
gr.setColor(255, 0, 0)
gr.drawString('Hello, World', 130, 160)
gr.setColor(0, 0, 255)
gr.drawString('Hello, World', 160, 220)
gr.setColor(255, 255, 255, 128)
gr.drawString('Hello, World', 190, 280)

]

#End

NOTE: Some of the functions (mainly from graphics library) are specific to certain global hooks. That is if you try to use them in a wrong hook the script wont do anything. Game doesnt actually warn about this so you may have to figure this one out on simple trial-and-error method.

Drawing Particles

Next we will try drawing particles to the screen. Again we need the scripting.tbl for this

Scripting.tbl

#Global Hooks

#End

Scripted Particles

To draw (or render) particles to the screen we need to use other Lua functions than what we used in the text example. The required function is createParticle() from Testing library (abbreviated ts.) and to place it into the $Simulation: hook. This function requires several arguments but for this example we only need to use few of them. As can be seen from the scripting.html the function uses vector objects for the first two arguments followed by two numerical ones and several others.

This means however that before we can actually start using the function we need to get some vector objects. Function to create these objects can be found from Math library (newVector()).

Scripting.tbl

#Global Hooks

$Simulation:

[

ts.createParticle(

]

#End