# G3N - Go 3D Game Engine

G3N is a basic (for now!) OpenGL 3D Game Engine written in Go.
G3N was heavily inspired and based on the [three.js](https://threejs.org/) Javascript 3D library.
If you are curious about G3N and would like to see it in action
we recommend that you install the [G3N demo program](https://github.com/g3n/g3nd).

# Dependencies

The engine needs an OpenGL driver installed in the system and
on Unix like systems depends on some C libraries that can be installed using the platform package manager.
In all cases it is necessary to have a C compiler installed.

* For Ubuntu/Debian-like Linux distributions, install `libgl1-mesa-dev` and `xorg-dev` packages.
* For CentOS/Fedora-like Linux distributions, install `libX11-devel libXcursor-devel libXrandr-devel libXinerama-devel mesa-libGL-devel libXi-devel` packages.
* Currently it was not tested on OS X. We encourage some feedback.
* For Windows it is recommended to have MingGW vx.x.x installed.

G3N supports spatial audio using external libraries but loads these libraries
dinamically on demand, so you can install G3N and build a 3D application
(not using audio) without installing these libraries.

The following libraries are necessary for the optional audio support:

* For Ubuntu/Debian-like Linux distributions, install `libopenal1` and `libvorbisfile3`
* For CentOS/Fedora-like Linux distributions, install `libopenal1` and `libvorbisfile3 (to be verified)`
* Currently it was not tested on OS X. We encourage some feedback.
* For Windows its is necessary to install the following dlls: OpenAL32.dll, libogg.dll, libvorbis.dll and libvorbisfile.dll.

G3N was only tested with Go1.7.4+

# Installation

The following command will download the engine and all its dependencies, compile and
install the packages. Make sure your GOPATH is set.

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

# Features

* Hierarchical scene graph. Any node can contain other nodes.
* Supports perspective and orthographic cameras. The camera can be controlled
  by the orbit control which allow zooming, rotation and panning using the mouse or keyboard.
* Suports ambient, directional, point and spot lights. Many lights can be added to the scene.
* Generators for primitive geometries such as: lines, box, sphere, cylinder and torus.
* Geometries can support multimaterials.
* Image textures can loaded from GIF, PNG or JPEG files and applied to materials.
* Loaders for the following 3D formats: Obj and Collada
* Text support allowing loading freetype fonts.
* Basic GUI supporting the widgets: label, image, button, checkbox, radiobutton,
  edit, scrollbar, slider, splitter, list, dropdown, tree, folder, window and layout managers
  (horizontal box, vertical box, grid, dock)
* Spatial audio support allowing playing sound from wave or Ogg Vorbis files.
* Users' applications can use their own vertex and fragment shaders.

# Basic application

The following code shows a basic G3N application 
([hellog3n](https://github.com/g3n/engine/tree/master/hellog3n))
which shows a wireframed sphere rotating.
You can install hellog3n using: `go get -u github.com/g3n/engine/hellog3n`

For more complex demos please see the [G3N demo program](https://github.com/g3n/g3nd).

```Go
package main

import (
	"github.com/g3n/engine/camera"
	"github.com/g3n/engine/core"
	"github.com/g3n/engine/geometry"
	"github.com/g3n/engine/gls"
	"github.com/g3n/engine/graphic"
	"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"
	"math"
	"runtime"
)

func main() {

	// Creates window and OpenGL context
	win, err := window.New("glfw", 800, 600, "Hello G3N", false)
	if err != nil {
		panic(err)
	}

	// OpenGL functions must be executed in the same thread where
	// the context was created (by window.New())
	runtime.LockOSThread()

	// Create OpenGL state
	gs, err := gls.New()
	if err != nil {
		panic(err)
	}

	// Creates scene for 3D objects
	scene := core.NewNode()

	// Adds white ambient light to the scene
	ambLight := light.NewAmbient(&math32.Color{1.0, 1.0, 1.0}, 0.5)
	scene.Add(ambLight)

	// Adds a perspective camera to the scene
	width, height := win.GetSize()
	aspect := float32(width) / float32(height)
	camera := camera.NewPerspective(65, aspect, 0.01, 1000)
	camera.SetPosition(0, 0, 5)

	// Add an axis helper
	axis := graphic.NewAxisHelper(2)
	scene.Add(axis)

	// Creates a wireframe sphere positioned at the center of the scene
	geom := geometry.NewSphere(2, 16, 16, 0, math.Pi*2, 0, math.Pi)
	mat := material.NewStandard(math32.NewColor(1, 1, 1))
	mat.SetSide(material.SideDouble)
	mat.SetWireframe(true)
	sphere := graphic.NewMesh(geom, mat)
	scene.Add(sphere)

	// Creates a renderer and adds default shaders
	rend := renderer.NewRenderer(gs)
	err = rend.AddDefaultShaders()
	if err != nil {
		panic(err)
	}

	// Sets window background color
	gs.ClearColor(0, 0, 0, 1.0)

	// Render loop
	for !win.ShouldClose() {

		// Clear buffers
		gs.Clear(gls.DEPTH_BUFFER_BIT | gls.STENCIL_BUFFER_BIT | gls.COLOR_BUFFER_BIT)

		// Rotates the sphere a bit around the Z axis (up)
		sphere.AddRotationY(0.005)

		// Render the scene using the specified camera
		rend.Render(scene, camera)

		// Update window and checks for I/O events
		win.SwapBuffers()
		win.PollEvents()
	}
}
```

<p align="center">
  <img style="float: right;" src="hellog3n/screenshot.png" alt="hellog3n Screenshot"/>
</p>

# To Do

G3N is a basic game engine. There is a lot of things to do.
We will soon insert here a list of the most important missing features.

# Documentation

For the engine API reference, please use
[![GoDoc](https://godoc.org/github.com/g3n/engine?status.svg)](https://godoc.org/github.com/g3n/engine).
We intend to add a user guide in the future.
Currently the best way to learn how to use the engine is to see the source code
of the demos from [G3ND](https://github.com/g3n/g3nd).

# Contributing

If you spot a bug or create a new feature you are encouraged to
send pull requests.