Devlog - I'm creating a game engine!

I'm creating a game engine!

Introduction to this great adventure

For a few weeks now I have been working regularly on a project that I think might be interesting to talk about, the creation of my video game engine in JavaScript and HTML5 based on canvas.

You are probably wondering why you chose HTML5 and JavaScript to create video games? The answer is less cool than the question, it is the competition of projects necessary for my school (Zone01 Normandie) and the fact that the languages ​​have everything necessary to carry out this project that led me to choose these technologies.

But actually these are not the languages ​​that I would have chosen as a base and I will surely embark on other adventures of this type with different languages ​​after the finalization of this one.

Architecture

So I got to work designing my video game engine, it will be made up of several classes including at least two main ones: The Game class which will manage the entire game area and the GameObject class allows you to generate the objects in our games and make them interact with each other.

To these classes I will add the CollideBox class which will allow me to manage the collision boxes of all objects.

The Game class has a GameLoop method which will be executed at each frame(image) of the game, a Draw method which will be called during each game loop.

As for the GameObject class, it has a Step method, and a Draw method.
The first executes each round of the game loop and the second each time the Draw method of the GameLoop class is called.

This allows you to theoretically create games by importing the Engine module into a project.
For displaying the sprites I chose to use the canva API which is built-in to HTML5 (built-in means it comes with it by default)
It will allow me to display all the sprites and recut the images in order to create animations which will be extremely useful to me!

After several days I am able to display animations, at a given speed, and detect collisions via my CollideBoxes.
And lots of other nice things that I'll let you see below:

The GameObject class

class GameObject{
    constructor(game) { // Initialize the GameObject
        this.x = 0
        this.y = 0 
        this.sprite_img = {file: undefined, col: 1, row: 1, fw: 1, fh: 1, step: 0, anim_speed: 0, scale: 1}
        this.loaded = false
        this.game = game
        this.kill = false
        this.collision = new CollideBox()

        game.gObjects.push(this)

    };
    setSprite(img_path, row=1, col=1, speed=12, scale=1) {
        var img = new Image();
        img.onload = () => {
            console.log("image loaded")
            this.sprite_img = {file: img, col: col, row: row, fw: img.width / col, fh: img.height / row, step: 0, anim_speed: speed, scale: scale}
            this.onSpriteLoaded()
        };
        img.src = img_path


    }
    onSpriteLoaded() {}
    draw(context, frame) { // Draw function of game object
        if (this.sprite_img.file != undefined) {


            let column = this.sprite_img.step % this.sprite_img.col;
            let row = Math.floor(this.sprite_img.step / this.sprite_img.col);

           // context.clearRect(this.x, this.y, this.sprite_img.fw, this.sprite_img.fh);
            context.drawImage(
                this.sprite_img.file,
                this.sprite_img.fw * column,
                this.sprite_img.fh * row,
                this.sprite_img.fw,
                this.sprite_img.fh,
                this.x,
                this.y,
                this.sprite_img.fw * this.sprite_img.scale,
                this.sprite_img.fh * this.sprite_img.scale
            );

            if (frame % Math.floor(60 / this.sprite_img.anim_speed) === 0) {
                // Mise à jour de step seulement à 12 fps
                if (this.sprite_img.step < this.sprite_img.row * this.sprite_img.col - 1) {
                    this.sprite_img.step += 1;
                } else {
                    this.sprite_img.step = 0;
                }
            }
        }
    }
    distance_to(pos) {
        return Math.sqrt((pos.x - this.x) ** 2 + (pos.y - this.y) ** 2)
    }

    collide_with(box) {
        if (box instanceof GameObject) {
            box = box.collision
        }
        return (
            this.collision.x < box.x + box.w &&
            this.collision.x + this.collision.w > box.x &&
            this.collision.y < box.y + box.h &&
            this.collision.y + this.collision.h > box.y
          )
    }
    onStep()   {};
}   

The Game class

class Game {
    constructor(width = 1400, height = 700) {
        this.gObjects = [];
        this.toLoad = [];
        this.timers = [];
        this.layers = [];
        this.canvas = document.getElementsByTagName("canvas")[0]

        this.canvas.width = width
        this.canvas.height = height
        this.context =  this.canvas.getContext("2d")
        this.context.globalCompositeOperation = 'source-over';
        this.inputs = {};
        this.mouse = {x: 0, y: 0}
        document.addEventListener('keydown', (e) => {
            this.inputs[e.key] = true;
        }, false);
        document.addEventListener('keyup', (e) => {
            this.inputs[e.key] = false;
        }, false);
        document.addEventListener('mousemove', (e) => {
            this.mouse.x = e.x;
            this.mouse.y = e.y;
        })
        document.addEventListener('mouseevent', (e) => {
            switch (e.button) {

            }
        })

    }
    draw(frame) {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
        console.log( this.canvas.width, this.canvas.heigh)
        for(let i = 0; i < this.gObjects.length; i ++) {
            this.gObjects[i].draw(this.context, frame)
        }

    }
    gLoop() {
        let fps = Math.floor(1000 / 60)
        console.log(fps)
        let clock = 0
        setInterval(() => {
            clock += 1
            for(let i = 0; i < this.gObjects.length; i ++) {

                if (this.gObjects[i] != undefined) {
                    if (this.gObjects[i].kill) {
                        this.gObjects.splice(i, 1);
                        continue;
                    }
                    this.gObjects[i].onStep();
                }


            }
            this.draw(Math.floor(clock))
               // context.l();

           //     console.log(clock)

           if (fps <= clock) {
            clock = 0
           } 

        }, fps)
    }
    keyboard_check(key) {
        return this.inputs[key] == true
    }
}

There are certainly a lot of optimization or other errors but everything is functional,
"Perfect!" will you tell me?
That would be way too simple.

The worries

After finishing this and starting to test the waters for creating a game with this engine, I learned some terrible news during a conversation with a colleague.

I imagine that you remember that the technology choices made were made to correspond to the requirements of my Zone01 school…
Well indeed the languages ​​chosen were good but I was not aware of an instruction which will very seriously handicap the project…
We were prohibited from using the Canva library!

As a reminder, this is the library that we use to display our images.

What’s next?

As I write this text I am also starting to completely redesign this game engine, without the use of canva.

This devlog is finished and you will have the rest of this story soon, don't worry.
For the next devlog I will definitely try a new format.

Hoping that this content has helped you, entertained you or at least educated you on a few subjects. I wish you a good end of the day and good coding.

DevLogs 1.1: The engine is finished, how does it work?

Previously

A few months ago I started creating my video game engine, I finished it... Quite a while ago, and with the help of several colleagues from Zone01 we even succeeded to create a game inspired by Super Mario Bros available on my Itch.io page.

Deciding the format to apply for this devlog took a lot of time, and I admit I delayed slightly or even completely pushed back the deadline for writing this one.
By patiently taking the excuse of my indecision for not working on this subject, I now find myself two months after the planned release date writing in the rest area of ​​the Rouen bus station while my canceled train forces me to wait an extra hour.

So let's ignore all the details of the architecture, this one having changed very little (apart from the adaptation by avoiding the use of canvases) since the first part of my devlog.
We will therefore talk about the project carried out, the way we worked as a team and the problems we encountered.
See this as feedback on this project, and I hope that you will be able to draw some lessons from this writing that will help you on one of your projects.

The project

The project was to recreate a Super Mario Bros in JavaScript and starting from scratch, at least in terms of the code.

The specifications were simple, we had to have a Mario game with several levels, a way to simply create new ones.
Also we had to create a scoreboard and a menu to adjust the options.

The difficulties of this project were:

• Horizontal scrolling of elements on the screen
• Optimization of elements not present on the screen

Scrolling because it requires all elements to scroll in the background relative to the player's position.
And optimizing elements that are not displayed on the screen helps reduce the resources needed to run the game without loss of performance.

After resolving these difficulties we published this game on my itch.io page where you can even go and test it.

This is how this devlog ends, now finished I will be able to write about other projects and/or other subjects.

If you're even a little interested in what I'm telling you, you can go see my different projects (including those in this devlog) on ​​github.

Have a nice rest of the day!

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