GettingStarted.md

Getting started with Potetre2D

Potetre2D is a 2D game engine written in C. It is designed to be simple and compact, and is made to be used with the Wren scripting language. As some French people may have noticed, the name is a pun on the French word "Peut-être" (maybe), as when the engine was first made, we were unsure if we could make a game engine that could fit less than 4Mb (And the orignal name, Picogine, was already taken).

First, you need to download the latest release of Potetre2D. You can find the latest release on the Releases page of the GitHub repository. You can also build the project yourself, see BUILDING.md for instructions on how to build the project.

Creating a project

The first thing you need to do is to create a project. To do so, you need to create a folder and copy the potetre2d executable in it. Then, you need to create a game.wren file in the same folder. This file will be the entry point of your game.

Open the game.wren file with your favorite text editor, and write the following code:

var WIDTH = 320
var HEIGHT = 240
var TITLE = "My Game"

/*
** Main game entry point
*/
class Game {
    /*
    ** Called when the game is started
    */
    static init(args) {
        System.print("Picogine Init!")
        Engine.init(WIDTH, HEIGHT, TITLE)
        Draw.clear()
    }

    /*
    ** Called every frame
    */
    static tick(dt) {

    }
}

The class Game is the entry point of your game. The init method is called when the game is started, and the tick method is called every frame if the engine is initialized (using the Engine.init method). If the engine is not initialized, the tick method will not be called and no window will be created. You can use this to create a command line program that can be used to generate assets for your game for example.

The dt parameter is the time elapsed since the last frame. This is useful to make your game run at the same speed on every computer. If the engine can't figure out the screen refresh rate, it will run at the fastest speed possible. Be careful!

Running the game

Execute the potetre2d executable. If everything went well, you should see a window with a white background. If the window is too small, you can resize i, it will automatically scale the game to fit the window.

Nothing happens? You may need to update your graphics drivers, the engine backend (Tigr) requires OpenGL 3.3 or later.

Drawing something

Now that you have a window, you may want to draw something on it. To do so, we're going to use the Surface module.

A surface is a 2D canvas that can be drawn on the screen, see this as a piece of paper that you can draw on. To create a surface, you can use the Surface.new method:

var surface = Surface.new(32, 32)

This will create a 32x32 pixels surface. You can also create a surface from an image file:

var surface = Surface.new_from_png("my_image.png")

In this case, the engine will load a PNG image from the file my_image.png and create a surface from it. The image will be converted to a 32 bits RGBA image if it is not already in this format.

Now that we have a surface, we can draw it on the screen. To do so, we need to use the draw method of the Surface module:

Surface.draw(surface, 0, 0)

This will draw the surface at the position (0, 0) on the screen. The position is relative to the top left corner of the screen. Don't forget to clear the screen before drawing anything, otherwise you will see the previous frame drawn on the screen.

Our code now looks like this:

var WIDTH = 320
var HEIGHT = 240
var TITLE = "My Game"

var surface = Surface.new_from_png("my_image.png")

/*
** Main game entry point
*/
class Game {
    /*
    ** Called when the game is started
    */
    static init(args) {
        System.print("Picogine Init!")
        Engine.init(WIDTH, HEIGHT, TITLE)
        Draw.clear()
    }

    /*
    ** Called every frame
    */
    static tick(dt) {
        Draw.clear()
        Surface.draw(surface, 0, 0)
    }
}

To infinity and beyond!

Now that you have a window and can draw something on it, you can start making your game. See the cheat sheet for a list of all the functions available here.