func programLoop(window *glfw.Window) {

	// the linked shader program determines how the data will be rendered
	shaders := compileShaders()
	shaderProgram := linkShaders(shaders)

	// VAO contains all the information about the data to be rendered
	VAO := createTriangleVAO()

	for !window.ShouldClose() {
		// poll events and call their registered callbacks
		glfw.PollEvents()

		// perform rendering
		gl.ClearColor(0.2, 0.5, 0.5, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT)

		// draw loop
		gl.UseProgram(shaderProgram)      // ensure the right shader program is being used
		gl.BindVertexArray(VAO)           // bind data
		gl.DrawArrays(gl.TRIANGLES, 0, 3) // perform draw call
		gl.BindVertexArray(0)             // unbind data (so we don't mistakenly use/modify it)
		// end of draw loop

		// swap in the rendered buffer
		window.SwapBuffers()
	}
}

func Run() {
	if err := glfw.Init(); err != nil {
		glog.Fatalln("failed to initialize glfw", err)
	}
	defer glfw.Terminate()

	setupWindowOptions()
	window, err := glfw.CreateWindow(WindowWidth, WindowHeight, "Game", nil, nil)
	if err != nil {
		panic(err)
	}
	window.MakeContextCurrent()

	//initilize Glow
	if err := gl.Init(); err != nil {
		panic(err)
	}

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)

	shaderSource, err := ReadShaders("colorShader")
	if err != nil {
		panic(err)
	}
	program, err := NewProgram(shaderSource)
	if err != nil {
		panic(err)
	}
	program.Use()

	sprite := &SpriteComponent{-.5, -.5, 1, 1}
	sprite.ReloadGraphics()

	vertAttrib := uint32(gl.GetAttribLocation(program.program, CStr("vertPosition")))
	gl.EnableVertexAttribArray(vertAttrib)
	gl.VertexAttribPointer(vertAttrib, 3, gl.FLOAT, false, 0, gl.PtrOffset(0))

	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)
	gl.ClearColor(1.0, 1.0, 1.0, 1.0)

	for !window.ShouldClose() {
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

		program.Use()

		gl.BindVertexArray(sprite.vaoID)
		gl.DrawArrays(gl.TRIANGLES, 0, 2*3)

		window.SwapBuffers()
		glfw.PollEvents()
	}
}

// New returns a newly created Screen
func New(width int, height int, fullscreen bool, FSAA int, name string) *Screen {
	window := &Screen{}

	C.SDL_Init(C.SDL_INIT_VIDEO)
	C.setGlContextAttributes()

	C.SDL_GL_SetAttribute(C.SDL_GL_DOUBLEBUFFER, 1)

	// Force hardware accel
	C.SDL_GL_SetAttribute(C.SDL_GL_ACCELERATED_VISUAL, 1)

	if FSAA > 0 {
		// FSAA (Fullscreen antialiasing)
		C.SDL_GL_SetAttribute(C.SDL_GL_MULTISAMPLEBUFFERS, 1)
		C.SDL_GL_SetAttribute(C.SDL_GL_MULTISAMPLESAMPLES, C.int(FSAA)) // 2, 4, 8
	}

	flags := C.SDL_WINDOW_OPENGL | C.SDL_RENDERER_ACCELERATED
	if fullscreen {
		flags = flags | C.SDL_WINDOW_FULLSCREEN
	}

	C.SDL_CreateWindowAndRenderer(C.int(width), C.int(height), C.Uint32(flags), &window.sdlWindow, &window.renderer)
	C.SDL_SetWindowTitle(window.sdlWindow, C.CString(name))
	C.SDL_GL_CreateContext(window.sdlWindow)

	if err := gl.Init(); err != nil {
		panic(err)
	}
	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)

	// Configure global settings
	gl.Enable(gl.BLEND)
	gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)

	gl.ClearColor(0.0, 0.0, 0.0, 1.0)
	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

	window.Width = width
	window.Height = height
	window.name = name
	window.shouldClose = false
	C.SDL_GL_SwapWindow(window.sdlWindow)

	window.startTime = time.Now()
	window.frameTime = time.Now()
	C.SDL_GL_SetSwapInterval(1)
	window.vsync = true

	return window
}

func draw(w *glfw.Window) {

	//Get the horizontal split size of the window
	sizex, sizey := w.GetSize()

	var eyesize mgl32.Vec2
	eyesize[0] = float32(sizex / 2.0)
	eyesize[1] = float32(sizey)

	gl.Enable(gl.SCISSOR_TEST)

	gl.Scissor(0, 0, int32(eyesize[0]), int32(eyesize[1]))
	gl.ClearColor(1, 0, 0, 1)
	gl.Clear(gl.COLOR_BUFFER_BIT)

	gl.Scissor(int32(eyesize[0]), 0, int32(eyesize[0]), int32(eyesize[1]))
	gl.ClearColor(0, 0, 1, 1)
	gl.Clear(gl.COLOR_BUFFER_BIT)

	gl.Disable(gl.SCISSOR_TEST)

}

func (me *Core) CreateWin(width, height int, name string) {
	glfw.WindowHint(glfw.ContextVersionMajor, 4)
	glfw.WindowHint(glfw.ContextVersionMinor, 5)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.Samples, 4) // AA4
	glfw.WindowHint(glfw.Resizable, glfw.False)
	win, err := glfw.CreateWindow(width, height, name, nil, nil)
	if err != nil {
		panic(err)
	}
	me.Win = win
	win.MakeContextCurrent()
	gl.ClearColor(1.0, 1.0, 1.0, 1.0)
	me.ClearOpt = gl.COLOR_BUFFER_BIT
}

func makeWindow() *glfw.Window {
	win, err := glfw.CreateWindow(windowWidth, windowHeight, "Tutorial #1", nil, nil)

	if err != nil {
		panic(err)
	}

	if err := gl.Init(); err != nil {
		panic(err)
	}

	win.MakeContextCurrent()
	gl.ClearColor(1.0, 1.0, 1.0, 1.0)

	return win
}

func (r *Renderer) Draw() {
	/* Clear screen */
	gl.ClearColor(0.9, 0.9, 0.9, 1.0)
	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

	/* Enable blending */
	gl.Enable(gl.BLEND)
	gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)

	/* Depth test */
	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)

	for _, pass := range r.Passes {
		pass.DrawPass(r.Scene)
	}
}

func initGL() string {
	// Initialize Glow
	if err := gl.Init(); err != nil {
		panic(err)
	}

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)
	fmt.Println("OpenGl shading version", gl.GoStr(gl.GetString(gl.SHADING_LANGUAGE_VERSION)))
	fmt.Println("OpenGl renderer", gl.GoStr(gl.GetString(gl.RENDERER)))

	// Configure global settings
	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)
	gl.ClearColor(0.5, 0.5, 0.5, 1.0)

	return version
}

func (screen *Screen) Init(title string, onCloseHandler func(), chip *chip8.Chip8) {
	var err error

	screen.chip = chip

	err = glfw.Init()

	if err != nil {
		panic(err)
	}

	window, err := glfw.CreateWindow(SCREEN_WIDTH, SCREEN_HEIGHT, title, nil, nil)
	if err != nil {
		panic(err)
	}

	window.MakeContextCurrent()

	// Initialize Glow
	if err := gl.Init(); err != nil {
		panic(err)
	}

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)

	gl.ClearColor(255.0, 0.0, 0.0, 0.0)                          //Set the cleared screen colour to black
	gl.Viewport(0, 0, int32(SCREEN_WIDTH), int32(SCREEN_HEIGHT)) //This sets up the viewport so that the coordinates (0, 0) are at the top left of the window

	for !window.ShouldClose() {
		// Do OpenGL stuff
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
		window.SwapBuffers()
		glfw.PollEvents()
	}

	onCloseHandler()

}

func main() {
	if err := glfw.Init(); err != nil {
		log.Fatalln("failed to inifitialize glfw:", err)
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.Resizable, glfw.False)
	glfw.WindowHint(glfw.ContextVersionMajor, 4)
	glfw.WindowHint(glfw.ContextVersionMinor, 1)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	window, err := glfw.CreateWindow(windowWidth, windowHeight, "Hello!", nil, nil)
	if err != nil {
		panic(err)
	}
	window.MakeContextCurrent()

	// Initialize Glow (go function bindings)
	if err := gl.Init(); err != nil {
		panic(err)
	}

	window.SetKeyCallback(keyCallback)

	// program loop
	for !window.ShouldClose() {
		// poll events and call their registered callbacks
		glfw.PollEvents()

		// perform rendering
		gl.ClearColor(0.2, 0.5, 0.5, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT)

		// swap in the rendered buffer
		window.SwapBuffers()
	}
}

func programLoop(window *win.Window) error {

	// the linked shader program determines how the data will be rendered
	vertShader, err := gfx.NewShaderFromFile("shaders/phong.vert", gl.VERTEX_SHADER)
	if err != nil {
		return err
	}

	fragShader, err := gfx.NewShaderFromFile("shaders/phong.frag", gl.FRAGMENT_SHADER)
	if err != nil {
		return err
	}

	program, err := gfx.NewProgram(vertShader, fragShader)
	if err != nil {
		return err
	}
	defer program.Delete()

	lightFragShader, err := gfx.NewShaderFromFile("shaders/light.frag", gl.FRAGMENT_SHADER)
	if err != nil {
		return err
	}

	// special shader program so that lights themselves are not affected by lighting
	lightProgram, err := gfx.NewProgram(vertShader, lightFragShader)
	if err != nil {
		return err
	}

	VAO := createVAO(cubeVertices, nil)
	lightVAO := createVAO(cubeVertices, nil)

	// ensure that triangles that are "behind" others do not draw over top of them
	gl.Enable(gl.DEPTH_TEST)

	camera := cam.NewFpsCamera(mgl32.Vec3{0, 0, 3}, mgl32.Vec3{0, 1, 0}, -90, 0, window.InputManager())

	for !window.ShouldClose() {

		// swaps in last buffer, polls for window events, and generally sets up for a new render frame
		window.StartFrame()

		// update camera position and direction from input evevnts
		camera.Update(window.SinceLastFrame())

		// background color
		gl.ClearColor(0, 0, 0, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT) // depth buffer needed for DEPTH_TEST

		// cube rotation matrices
		rotateX := (mgl32.Rotate3DX(mgl32.DegToRad(-45 * float32(glfw.GetTime()))))
		rotateY := (mgl32.Rotate3DY(mgl32.DegToRad(-45 * float32(glfw.GetTime()))))
		rotateZ := (mgl32.Rotate3DZ(mgl32.DegToRad(-45 * float32(glfw.GetTime()))))

		// creates perspective
		fov := float32(60.0)
		projectTransform := mgl32.Perspective(mgl32.DegToRad(fov),
			float32(window.Width())/float32(window.Height()),
			0.1,
			100.0)

		camTransform := camera.GetTransform()
		lightPos := mgl32.Vec3{0.6, 1, 0.1}
		lightTransform := mgl32.Translate3D(lightPos.X(), lightPos.Y(), lightPos.Z()).Mul4(
			mgl32.Scale3D(0.2, 0.2, 0.2))

		program.Use()
		gl.UniformMatrix4fv(program.GetUniformLocation("view"), 1, false, &camTransform[0])
		gl.UniformMatrix4fv(program.GetUniformLocation("project"), 1, false,
			&projectTransform[0])

		gl.BindVertexArray(VAO)

		// draw each cube after all coordinate system transforms are bound

		// obj is colored, light is white
		gl.Uniform3f(program.GetUniformLocation("material.ambient"), 1.0, 0.5, 0.31)
		gl.Uniform3f(program.GetUniformLocation("material.diffuse"), 1.0, 0.5, 0.31)
		gl.Uniform3f(program.GetUniformLocation("material.specular"), 0.5, 0.5, 0.5)
		gl.Uniform1f(program.GetUniformLocation("material.shininess"), 32.0)

		lightColor := mgl32.Vec3{
			float32(math.Sin(glfw.GetTime() * 1)),
			float32(math.Sin(glfw.GetTime() * 0.35)),
			float32(math.Sin(glfw.GetTime() * 0.65)),
		}

		diffuseColor := mgl32.Vec3{
			0.5 * lightColor[0],
			0.5 * lightColor[1],
			0.5 * lightColor[2],
		}
		ambientColor := mgl32.Vec3{
			0.2 * lightColor[0],
			0.2 * lightColor[1],
			0.2 * lightColor[2],
		}

		gl.Uniform3f(program.GetUniformLocation("light.ambient"),
//.........这里部分代码省略.........

// SetClearColor sets the color when the screen is cleared for redrawing
func (window *Screen) SetClearColor(r float32, g float32, b float32, a float32) {
	gl.ClearColor(r, g, b, a)
}

func main() {
	if err := glfw.Init(); err != nil {
		log.Fatalln("failed to initialize glfw:", err)
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.Resizable, glfw.False)
	glfw.WindowHint(glfw.ContextVersionMajor, 4)
	glfw.WindowHint(glfw.ContextVersionMinor, 1)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	window, err := glfw.CreateWindow(windowWidth, windowHeight, "Cube", nil, nil)

	if err != nil {
		panic(err)
	}
	window.MakeContextCurrent()

	// Initialize Glow
	if err := gl.Init(); err != nil {
		panic(err)
	}

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)

	// Configure the vertex and fragment shaders
	program, err := newProgram(vertexShader, fragmentShader)

	if err != nil {
		panic(err)
	}

	gl.UseProgram(program)

	projection := mgl32.Perspective(mgl32.DegToRad(45.0), float32(windowWidth)/windowHeight, 0.1, 10.0)
	projectionUniform := gl.GetUniformLocation(program, gl.Str("projection\x00"))
	gl.UniformMatrix4fv(projectionUniform, 1, false, &projection[0])

	camera := mgl32.LookAtV(mgl32.Vec3{3, 3, 3}, mgl32.Vec3{0, 0, 0}, mgl32.Vec3{0, 1, 0})
	cameraUniform := gl.GetUniformLocation(program, gl.Str("camera\x00"))
	gl.UniformMatrix4fv(cameraUniform, 1, false, &camera[0])

	model := mgl32.Ident4()
	modelUniform := gl.GetUniformLocation(program, gl.Str("model\x00"))
	gl.UniformMatrix4fv(modelUniform, 1, false, &model[0])

	textureUniform := gl.GetUniformLocation(program, gl.Str("tex\x00"))
	gl.Uniform1i(textureUniform, 0)

	gl.BindFragDataLocation(program, 0, gl.Str("outputColor\x00"))

	// Load the texture
	texture, err := newTexture("square.png")
	if err != nil {
		panic(err)
	}

	// Configure the vertex data
	var vao uint32
	gl.GenVertexArrays(1, &vao)
	gl.BindVertexArray(vao)

	var vbo uint32
	gl.GenBuffers(1, &vbo)
	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
	gl.BufferData(gl.ARRAY_BUFFER, len(cubeVertices)*4, gl.Ptr(cubeVertices), gl.STATIC_DRAW)

	vertAttrib := uint32(gl.GetAttribLocation(program, gl.Str("vert\x00")))
	gl.EnableVertexAttribArray(vertAttrib)
	gl.VertexAttribPointer(vertAttrib, 3, gl.FLOAT, false, 5*4, gl.PtrOffset(0))

	texCoordAttrib := uint32(gl.GetAttribLocation(program, gl.Str("vertTexCoord\x00")))
	gl.EnableVertexAttribArray(texCoordAttrib)
	gl.VertexAttribPointer(texCoordAttrib, 2, gl.FLOAT, false, 5*4, gl.PtrOffset(3*4))

	// Configure global settings
	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)
	gl.ClearColor(1.0, 1.0, 1.0, 1.0)

	angle := 0.0
	previousTime := glfw.GetTime()

	for !window.ShouldClose() {
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

		// Update
		time := glfw.GetTime()
		elapsed := time - previousTime
		previousTime = time

		angle += elapsed
		model = mgl32.HomogRotate3D(float32(angle), mgl32.Vec3{0, 1, 0})

		// Render
		gl.UseProgram(program)
		gl.UniformMatrix4fv(modelUniform, 1, false, &model[0])

		gl.BindVertexArray(vao)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	defer helpclear.DeleteString()
	var helpescape *String = font.NewString("ESC: quit")
	defer helpescape.DeleteString()

	var vbo *VBO
	if vbo, err = NewVBOQuad(0, 0, float32(texture.Size.X), float32(texture.Size.Y)); err != nil {
		panic(err)
	}
	defer vbo.DeleteVBO()

	var cnt float32 = 0

	// while there's no request to close the window
	for !window.ShouldClose() {
		cnt += 1

		// get the texture of the window because it may have changed since creation
		width, height := window.GetFramebufferSize()
		wwidth, _ := window.GetSize()
		gRetinaScale = float32(width) / float32(wwidth)

		//fmt.Printf("x=%d y=%d wx=%d wy=%d\n", width, height, wwidth, wheight)

		if cnt >= float32(width) {
			cnt = 0
		}

		var matrix Matrix2x3 = IdentityMatrix2x3()
		matrix = matrix.Translate(-1.0, 1.0)
		matrix = matrix.Scale(2.0/float32(width), -2.0/float32(height))

		// clear it all out
		gl.Viewport(0, 0, int32(width), int32(height))
		gl.ClearColor(0.0, 0.0, 0.0, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

		gl.Enable(gl.BLEND)
		gl.BlendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA)
		gl.BlendEquation(gl.FUNC_ADD)

		var matrix3 Matrix2x3 = matrix.Scale(gZoom, gZoom)
		matrix3 = matrix3.Translate(gOffX, gOffY)

		// draw the grid
		if true {
			vbo.Bind()
			progGrid.UseProgram()

			color1 := [4]float32{.4, .4, .4, 1}
			color2 := [4]float32{.9, .9, .9, 1}
			grid := [3]float32{float32(texture.Size.X), float32(texture.Size.Y), 8 / gZoom}
			//fmt.Printf("%.2f %.2f %.2f %.2f\n", grid[0], grid[1], grid[2], grid[3])
			progGrid.ProgramUniformMatrix4fv("ModelviewMatrix", matrix3.Array())
			progGrid.ProgramUniform4fv("color1", color1)
			progGrid.ProgramUniform4fv("color2", color2)
			progGrid.ProgramUniform3fv("grid", grid)

			if err = progGrid.ValidateProgram(); err != nil {
				panic(err)
			}

			vbo.Draw()

			vbo.Unbind()
			progGrid.UnuseProgram()
		}

// BackGroundColor - set background color for the scene
func (glRenderer *OpenglRenderer) BackGroundColor(r, g, b, a float32) {
	gl.ClearColor(r, g, b, a)
}

/* Clear the frame buffer. Make sure its bound first */
func (f *FrameBuffer) Clear() {
    gl.ClearColor(f.ClearColor.R, f.ClearColor.G, f.ClearColor.B, f.ClearColor.A)
    gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
}

func (p *LightPass) DrawPass(scene *Scene) {
	/* use light pass shader */
	p.Material.Use()
	shader := p.Material.Shader

	/* compute camera view projection inverse */
	vp := scene.Camera.Projection.Mul4(scene.Camera.View)
	vp_inv := vp.Inv()
	shader.Matrix4f("cameraInverse", &vp_inv[0])

	/* clear */
	gl.ClearColor(0.9, 0.9, 0.9, 1.0)
	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

	/* set blending mode to additive */

	gl.DepthMask(false)

	/* draw lights */
	lights := scene.FindLights()
	last := len(lights) - 1

	for i, light := range lights {
		if i == 1 {
			/* first light pass we want the shader to restore the depth buffer
			 * then, disable depth masking so that multiple lights can be drawn */
			gl.BlendFunc(gl.ONE, gl.ONE)
		}
		if i == last {
			gl.DepthMask(true)
		}

		/* draw shadow pass for this light into shadow map */
		p.Shadows.DrawPass(scene, &light)

		/* use light pass shader */
		p.Material.Use()

		/* compute world to lightspace (light view projection) matrix */
		lp := light.Projection
		lv := mgl.LookAtV(light.Position, mgl.Vec3{}, mgl.Vec3{0, 1, 0}) // only for directional light
		lvp := lp.Mul4(lv)
		shader.Matrix4f("light_vp", &lvp[0])

		/* set light uniform attributes */
		shader.Vec3("light.Position", &light.Position)
		shader.Vec3("light.Color", &light.Color)
		shader.Int32("light.Type", int32(light.Type))
		shader.Float("light.Range", light.Range)
		shader.Float("light.attenuation.Constant", light.Attenuation.Constant)
		shader.Float("light.attenuation.Linear", light.Attenuation.Linear)
		shader.Float("light.attenuation.Quadratic", light.Attenuation.Quadratic)

		/* render light */
		gl.Viewport(0, 0, int32(scene.Camera.Width), int32(scene.Camera.Height))
		p.quad.Draw()
	}

	/* reset GL state */
	gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
}

func Main() {
	err := glfw.Init()
	if err != nil {
		panic(err)
	}
	defer glfw.Terminate()

	glfw.WindowHint(glfw.Resizable, glfw.False)
	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 2)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	window, err := glfw.CreateWindow(WindowWidth, WindowHeight, "Cube", nil, nil)
	Window = window
	if err != nil {
		panic(err)
	}
	window.MakeContextCurrent()

	// Initialize Glow
	if err := gl.Init(); err != nil {
		panic(err)
	}

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL version", version)

	// Configure the vertex and fragment shaders
	program, err := newProgram("SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader")
	if err != nil {
		panic(err)
	}
	gl.UseProgram(program)

	projection := mgl32.Perspective(mgl32.DegToRad(45.0), float32(WindowWidth)/WindowHeight, 0.1, 10.0)
	projectionUniform := gl.GetUniformLocation(program, gl.Str("projection\x00"))
	gl.UniformMatrix4fv(projectionUniform, 1, false, &projection[0])

	camera := mgl32.LookAtV(mgl32.Vec3{3, 3, 3}, mgl32.Vec3{0, 0, 0}, mgl32.Vec3{0, 1, 0})
	cameraUniform := gl.GetUniformLocation(program, gl.Str("camera\x00"))
	gl.UniformMatrix4fv(cameraUniform, 1, false, &camera[0])

	model := mgl32.Ident4()
	modelUniform := gl.GetUniformLocation(program, gl.Str("model\x00"))
	gl.UniformMatrix4fv(modelUniform, 1, false, &model[0])

	textureUniform := gl.GetUniformLocation(program, gl.Str("tex\x00"))
	gl.Uniform1i(textureUniform, 0)

	gl.BindFragDataLocation(program, 0, gl.Str("outputColor\x00"))
	// Configure global settings
	gl.Enable(gl.DEPTH_TEST)
	gl.DepthFunc(gl.LESS)
	gl.ClearColor(1.0, 1.0, 1.0, 1.0)

	angle := 0.0
	previousTime := glfw.GetTime()

	width, height := window.GetSize()
	window.SetCursorPos(float64(width/2), float64(height/2))
	window.SetKeyCallback(input.OnKey)
	window.SetCursorPosCallback(input.OnCursor)
	window.SetMouseButtonCallback(input.OnMouse)

	meshes.LoadColladaCube("cube.dae")

	for !player.ShouldClose {
		gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

		// Update
		time := glfw.GetTime()
		elapsed := time - previousTime
		previousTime = time

		angle += elapsed
		model = mgl32.HomogRotate3D(float32(angle), mgl32.Vec3{0, 1, 0})

		// Render
		gl.UseProgram(program)
		// gl.UniformMatrix4fv(modelUniform, 1, false, &model[0])
		player.MainPlayer.Draw(program)
		for _, element := range game.Universe {
			(element).Draw(program)
		}

		// Maintenance
		window.SwapBuffers()
		glfw.PollEvents()
	}
}

func (context *Context) SetBackgroundColor(color *Colorf) {
	gl.ClearColor(color[0], color[1], color[2], color[3])
}

func programLoop(window *glfw.Window) {

	// the linked shader program determines how the data will be rendered
	vertexShader := compileShader(vertexShaderSource, gl.VERTEX_SHADER)
	fragmentShaderBlue := compileShader(fragmentShaderBlueSource, gl.FRAGMENT_SHADER)
	shaderProgramBlue := linkShaders([]uint32{vertexShader, fragmentShaderBlue})
	fragmentShaderRed := compileShader(fragmentShaderRedSource, gl.FRAGMENT_SHADER)
	shaderProgramRed := linkShaders([]uint32{vertexShader, fragmentShaderRed})

	// shader objects are not needed after they are linked into a program object
	gl.DeleteShader(vertexShader)
	gl.DeleteShader(fragmentShaderBlue)
	gl.DeleteShader(fragmentShaderRed)

	vertices1 := []float32{
		0.2, 0.2, 0.0, // top right
		0.2, -0.8, 0.0, // bottom right
		-0.8, -0.8, 0.0, // bottom left
		-0.8, 0.2, 0.0, // top left
	}

	indices1 := []uint32{
		0, 1, 3, // first triangle
		1, 2, 3, // second triangle
	}

	VAO1 := createTriangleVAO(vertices1, indices1)

	vertices2 := []float32{
		0.2, 0.6, 0.0, // top
		0.6, -0.2, 0.0, // bottom right
		-0.2, -0.2, 0.0, // bottom left
	}

	indices2 := []uint32{
		0, 1, 2, // only triangle
	}

	VAO2 := createTriangleVAO(vertices2, indices2)

	for !window.ShouldClose() {
		// poll events and call their registered callbacks
		glfw.PollEvents()

		// perform rendering
		gl.ClearColor(0.2, 0.5, 0.5, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT)

		// draw loop

		// draw rectangle
		gl.PolygonMode(gl.FRONT_AND_BACK, gl.LINE)
		gl.UseProgram(shaderProgramRed)
		gl.BindVertexArray(VAO1)
		gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, unsafe.Pointer(nil))
		gl.BindVertexArray(0)

		// draw triangle
		gl.PolygonMode(gl.FRONT_AND_BACK, gl.FILL)
		gl.UseProgram(shaderProgramBlue)
		gl.BindVertexArray(VAO2)
		gl.DrawElements(gl.TRIANGLES, 3, gl.UNSIGNED_INT, unsafe.Pointer(nil))
		gl.BindVertexArray(0)

		// end of draw loop

		// swap in the rendered buffer
		window.SwapBuffers()
	}
}