g3n-engine

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G3N - Go 3D Game Engine

G3N (pronounced "gen") is an OpenGL 3D Game Engine written in Go. It can be used to write cross-platform Go applications that show rich and dynamic 3D representations - not just games. A basic integrated GUI framework is provided, and 3D spatial audio is supported through OpenAL.

### To see G3N in action try the G3N demo or the Gokoban award winning game.

<img style="float: right;" src="https://raw.githubusercontent.com/g3n/g3nd/master/data/images/g3nd_screenshots.png" alt="G3ND In Action"/>

## Highlighted Projects Using G3N

• Gokoban - 3D Puzzle Game (1st place in the 2017 Gopher Game Jam)
• go-tsne (dimensionality reduction particularly well suited for visualizing high-dimensional datasets)
• G3N Server-Side Rendering

## Dependencies

Go 1.8+ is required. The engine also requires the system to have an OpenGL driver and a GCC-compatible C compiler.

On Unix-based systems the engine depends on some C libraries that can be installed using the appropriate distribution package manager. See below for OS specific requirements.

### Ubuntu/Debian-like

$ sudo apt-get install xorg-dev libgl1-mesa-dev libopenal1 libopenal-dev libvorbis0a libvorbis-dev libvorbisfile3

### Fedora

$ sudo dnf -y install xorg-x11-proto-devel mesa-libGL mesa-libGL-devel openal-soft openal-soft-devel libvorbis libvorbis-devel glfw-devel libXi-devel

### CentOS 7

Enable the EPEL repository:

$ sudo yum -y install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

Then install the same packages as for Fedora - remember to use yum instead of dnf for the package installation command.

### Windows

The necessary audio libraries sources and DLLs are supplied but they need to be installed manually. Please see Audio libraries for Windows for details. We tested the Windows build using the mingw-w64 toolchain (you can download this file in particular).

### macOS

Install the development files of OpenAL and Vorbis using Homebrew:

brew install libvorbis openal-soft

## Installation

The following command will download and install the engine along with all its Go dependencies:

go get -u github.com/g3n/engine/...

## Features

• Cross-platform: Windows, Linux, and macOS
• Integrated GUI (graphical user interface) with many widgets
• Hierarchical scene graph - nodes can contain other nodes
• 3D spatial audio via OpenAL (.wav, .ogg)
• Real-time lighting: ambient, directional, point, and spot lights
• Physically-based rendering: fresnel reflectance, geometric occlusion, microfacet distribution
• Model loaders: glTF (.gltf, .glb), Wavefront OBJ (.obj), and COLLADA (.dae)
• Geometry generators: box, sphere, cylinder, torus, etc...
• Geometries support morph targets and multimaterials
• Support for animated sprites based on sprite sheets
• Perspective and ortographic cameras
• Text image generation and support for TrueType fonts
• Image textures can be loaded from GIF, PNG or JPEG files
• Animation framework for position, rotation, and scale of objects
• Support for user-created GLSL shaders: vertex, fragment, and geometry shaders
• Integrated basic physics engine (experimental/incomplete)
• Support for HiDPI displays

<img style="float: right;" src="https://github.com/g3n/g3n.github.io/raw/master/img/g3n_banner_small.png" alt="G3N Banner"/>

## Hello G3N

The code below is a basic "hello world" application (hellog3n) that shows a blue torus and a button that when clicked makes the torus red:

package main

import (
	"github.com/g3n/engine/app"
	"github.com/g3n/engine/camera"
	"github.com/g3n/engine/camera/control"
	"github.com/g3n/engine/core"
	"github.com/g3n/engine/geometry"
	"github.com/g3n/engine/gls"
	"github.com/g3n/engine/graphic"
	"github.com/g3n/engine/gui"
	"github.com/g3n/engine/light"
	"github.com/g3n/engine/material"
	"github.com/g3n/engine/math32"
	"github.com/g3n/engine/renderer"
	"github.com/g3n/engine/window"
	"time"
)

func main() {

	// Create application and scene
	a := app.App()
	scene := core.NewNode()

	// Set the scene to be managed by the gui manager
	gui.Manager().Set(scene)

	// Create perspective camera
	cam := camera.NewPerspective(65, 1, 0.01, 1000)
	cam.SetPosition(0, 0, 3)
	scene.Add(cam)

	// Set up orbit control for the camera
	control.NewOrbitControl(cam)

	// Set up callback to update viewport and camera aspect ratio when the window is resized
	onResize := func(evname string, ev interface{}) {
		// Get framebuffer size and update viewport accordingly
		width, height := a.GetSize()
		a.Gls().Viewport(0, 0, int32(width), int32(height))
		// Update the camera's aspect ratio
		cam.SetAspect(float32(width) / float32(height))
	}
	a.Subscribe(window.OnWindowSize, onResize)
	onResize("", nil)

	// Create a blue torus and add it to the scene
	geom := geometry.NewTorus(1, .4, 12, 32, math32.Pi*2)
	mat := material.NewPhong(math32.NewColor("DarkBlue"))
	mesh := graphic.NewMesh(geom, mat)
	scene.Add(mesh)

	// Create and add a button to the scene
	btn := gui.NewButton("Make Red")
	btn.SetPosition(100, 40)
	btn.SetSize(40, 40)
	btn.Subscribe(gui.OnClick, func(name string, ev interface{}) {
		mat.SetColor(math32.NewColor("DarkRed"))
	})
	scene.Add(btn)

	// Create and add lights to the scene
	scene.Add(light.NewAmbient(&math32.Color{1.0, 1.0, 1.0}, 0.8))
	pointLight := light.NewPoint(&math32.Color{1, 1, 1}, 5.0)
	pointLight.SetPosition(1, 0, 2)
	scene.Add(pointLight)

	// Create and add an axis helper to the scene
	scene.Add(graphic.NewAxisHelper(0.5))

	// Set background color to gray
	a.Gls().ClearColor(0.5, 0.5, 0.5, 1.0)

	// Run the application
	a.Run(func(renderer *renderer.Renderer, deltaTime time.Duration) {
		a.Gls().Clear(gls.DEPTH_BUFFER_BIT | gls.STENCIL_BUFFER_BIT | gls.COLOR_BUFFER_BIT)
		renderer.Render(scene, cam)
	})
}

<img style="float: right;" src="https://github.com/g3n/demos/blob/master/hellog3n/screenshot.png" alt="hellog3n Screenshot"/>

You can download and install hellog3n via:

go get -u github.com/g3n/demos/hellog3n

For more complex demos please see the G3N demo program.

## Documentation

The complete engine API reference can be found here: .

There is also the beginning of a Getting Started Guide, and a newly created list of Guides and Tutorials:

• Getting Started
• Guides and Tutorials

Along with those, a good way to learn how to use the engine is to see the source code of G3ND - the G3N demo.

## Contributing

If you find a bug or create a new feature you are encouraged to send pull requests!

## Community

Join our channel on Gophers Slack (Click here to register for Gophers Slack). It's a great way to have your questions answered quickly by the G3N community.