Harujion Engine

In case you don’t know, back in 2021 travelers in China would sometimes get quarantined for possible contact with COVID carriers. During the quarantine we need to stay in a designated hotel or something for two weeks.

Harujion is a small 2d engine I made during quarantine (because I got nothing else to do). It’s heavily inspired by Love2D.

I’m working on a similar project with one of my friend called amore2d. It’s not ready for release yet, but now that I’m much more familiar with Lua APIs, I made a much better Lua-C++ interop layer.

Features

• Modern OpenGL 2D Renderer (4.5 Core Profile, Direct State Access)
• Uses LuaJIT instead of vanilla Lua
• Lua Scripting Support
  • Window
  • Keyboard
  • Mouse
  • Renderer
  • Audio
  • Built-in common 2D graphics objects

Demo video: Flappy Bird

Assets are from this repo.

Sample Lua Code: Player script for the Flappy Bird game

This is a simple piece of code I used in the Flappy Bird game. It’s mainly for demo purpose so there’s nothing fancy in it, but it works well.

-- load classic.lua for Lua OOP
local Object = require("classic.lua")

-- declare the Player class
local Player = Object:extend()

-- Player constructor
function Player:new()
    -- load the animation sprites
    self.sprites = {
        haru.Sprite.new("flappy/yellowbird-midflap.png", 32),
        haru.Sprite.new("flappy/yellowbird-downflap.png", 32),
        haru.Sprite.new("flappy/yellowbird-midflap.png", 32),
        haru.Sprite.new("flappy/yellowbird-upflap.png", 32)
    }
    self.v = 0.0 -- vertical velocity
    self.y = 0.0 -- vertical position
    self.sprite_timer = 0.0 -- animation timer
    self.sprite_idx = 1 -- current animation frame
end

function Player:jump()
    -- jumping is simply changing the vertical velocity
    self.v = 5.0
end

function Player:update(deltaTime)
    -- update velocity and position
    self.v = self.v - 10 * deltaTime
    self.y = self.y + self.v * deltaTime

    -- update sprite frame animation
    self.sprite_timer = self.sprite_timer + deltaTime
    if self.sprite_timer > 0.1 then -- 0.1s per animation frame
        self.sprite_timer = self.sprite_timer - 0.1

        self.sprite_idx = self.sprite_idx + 1 -- show next frame
        if self.sprite_idx == 5 then -- wrap back to the first frame
            self.sprite_idx = 1
        end
    end
end

function Player:draw()
    -- draw the sprite and rotate it based on velocity
    self.sprites[self.sprite_idx]:draw(0.0, self.y, self.v * 0.1)
end

return Player

Lua APIs

I loosely followed the Love2D API (which is basically a wrapper around SDL and SDL_Renderer).

Window

• haru.window.close(): Close the window
• haru.window.getFramebufferSize(): Get the framebuffer size
• haru.window.setTitle(title): Change the window title

Keyboard

• haru.keyboard.pressed(key): Check if a key is being pressed
• haru.keyboard.justPressed(key): Check if a key is pressed in this frame
• haru.keyboard.justReleased(key): Check if a key is released in this frame

Mouse

• haru.mouse.pressed(button): Check if a mouse button is being pressed
• haru.mouse.justPressed(button): Check if a mouse button is pressed in this frame
• haru.mouse.justReleased(button): Check if a mouse button is released in this frame
• haru.mouse.normalizedPosition(): Get mouse normalized position (0.0 ~ 1.0)
• haru.mouse.setCursor(enable): Enable or hide the cursor

Renderer

• haru.renderer.setMatrixOrtho(left, right, bottom, top): Set the camera matrix
• haru.renderer.setClearColor(r, g, b[, a]): Change the renderer clear color
• haru.renderer.setDrawColor(r, g, b[, a]): Change the renderer draw color
• haru.renderer.drawPoint(x, y[, size]): Draw a point
• haru.renderer.drawLine(x0, y0, x1, y1[, width]): Draw a line
• haru.renderer.drawRect(x0, y0, x1, y1[, width]): Draw a rect (only the outline)
• haru.renderer.fillRect(x0, y0, x1, y1): Fill a rect with draw color

Audio

• haru.audio.loadBank(filename): Load a FMOD audio bank
• haru.audio.setVolume(volume): Change the global volume
• haru.audio.getEventDescription(eventPath): Get the event description for a FMOD event
• haru.audio.fireOneShotEvent(event): Play a one-shot FMOD event

Built-in Lua Objects (Texture, Sprite, SpriteFont, Tileset)

Texture

• haru.Texture.load(filename, filter, clamp, mipmap): Load a texture (returns a texture object)
• haru.Texture:getSize(): Get the texture size

Sprite

• haru.Sprite.new(texture): Create a sprite from a texture
• haru.Sprite:setPixelRect(x, y, w, h): Set the sprite to use a rect on a texture atlas (in pixels)
• haru.Sprite:setPixelPivot(x, y): Set the sprite pivot (in pixels)
• haru.Sprite:setFlip(x, y): Set the sprite to flip horizontally or vertically
• haru.Sprite:draw(x, y, rotation, scaleX, scaleY): Draw the sprite

SpriteFont

• haru.SpriteFont.new(fontFilename): Load a sprite font (bitmap font)
• haru.SpriteFont:getGlyphPixelSize(): Get the size of one glyph in the bitmap font
• haru.SpriteFont:draw(x, y, text, size): Draw text using the sprite font

Tileset

• haru.Tileset.new(texture, tileWidth, tileHeight, spacing): Load a tileset
• haru.Tileset:getTileSize(): Get the size of one tile in the tileset
• haru.Tileset:draw(index, x, y): Draw the indexth tile in the tileset