Oak

A pure Go game engine

Installation
Motivation
Features
Support
Quick Start
Implementation and Examples
Finished Games

Installation

go get -u github.com/oakmound/oak/v2/...

Or in GOPATH mode (not using go modules):

go get -u github.com/oakmound/oak/...

Motivation

The initial version of oak was made to support Oakmound Studio's game, Agent Blue, and was developed in parallel. Oak supports Windows with no dependencies and Linux with limited audio dependencies. We don't own a machine to check with, but hypothetically it supports OSX as well. We hope that users will be able to make great pure Go games with oak and welcome improvements.

Because Oak wants to have as few non-Go dependencies as possible, Oak does not use OpenGL or GLFW. We're open to adding support for these in the future for performance gains, but we always want an alternative that requires zero or near-zero dependencies.

Features

Window Rendering
- Windows and key events forked from shiny
- Logical frame rate distinct from Draw rate
- Fullscreen, Window Positioning support
- Auto-scaling for screen size changes
Image Management
- render.Renderable interface
- Sprite Sheet Batch Loading at startup
- Manipulation
  - render.Modifiable interface
  - Built in Transformations and Filters
  - Some built-ins via gift
  - Extensible Modification syntax func(image.Image) *image.RGBA
- Built in Renderable types covering common use cases
  - Sprite, Sequence, Switch, Composite
  - Primitive builders, ColorBox, Line, Bezier
  - History-tracking Reverting
- Primarily 2D
Particle System
- Click to see gif captured in examples/particle-demo
Mouse Handling
- Click Collision
- MouseEnter / MouseExit reaction events
- Drag Handling
Joystick Support
- Click to see gif captured in examples/joystick-viz
Audio Support
- Positional filters to pan and scale audio based on a listening position
Collision
- Collision R-Tree forked from rtreego
- 2D Raycasting
- Collision Spaces
  - Attachable to Objects
  - Auto React to collisions through events
  - OnHit bindings func(s1,s2 *collision.Space)
  - Start/Stop collision with targeted objects
2D Physics System
- Vectors
  - Attachable to Objects / Renderables
  - Friction
Event Handler, Bus
- PubSub system: event.CID can Bind(fn,eventName) and Trigger(eventName) events
Shaping
- Convert shapes into:
  - Containment checks
  - Outlines
  - 2D arrays
Custom Console Commands
Logging
- Swappable with custom implementations
- Default Implementation: 4 log levels, writes to file and stdout

Support

For discussions not significant enough to be an Issue or PR, see the #oak channel on the gophers slack.

Quick Start

This is an example of the most basic oak program:

oak.Add("firstScene",
    // Initialization function
    func(prevScene string, inData interface{}) {}, 
    // Loop to continue or stop the current scene
    func() bool {return true}, 
    // Exit to transition to the next scene
    func() (nextScene string, result *scene.Result) {return "firstScene", nil}) 
oak.Init("firstScene")

See the examples folder for longer demos, godoc for reference documentation, and the wiki for more guided feature sets, tutorials and walkthroughs.

Implementation and Examples

Platformer

Build up to having a simple platforming game by doing the following: Setup a character, get it to move, set basic gravity, get it to jump, make it only jump on solid ground, put it all together.

char := entities.NewMoving(100, 100, 16, 32,
	render.NewColorBox(16, 32, color.RGBA{255, 0, 0, 255}),
nil, 0, 0)

char.Bind(func(id int, nothing interface{}) int {
	char := event.GetEntity(id).(*entities.Moving)

	// Move left and right with A and D
	if oak.IsDown(key.A) {
		char.Delta.SetX(-char.Speed.X())
	} else if oak.IsDown(key.D) {
		char.Delta.SetX(char.Speed.X())
	} else {
		char.Delta.SetX(0)
	}
	oldX, oldY := char.GetPos()
    char.ShiftPos(char.Delta.X(), char.Delta.Y())
	return 0
}, event.Enter)