Tutorial Complete
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311
main.go
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311
main.go
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package main
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/* OpenGL & Go Tutorial
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* https://kylewbanks.com/blog/tutorial-opengl-with-golang-part-1-hello-opengl
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*
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* Vertex/Fragment Shader Explanation
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* https://www.quora.com/What-is-a-vertex-shader-and-what-is-a-fragment-shader/answer/Harold-Serrano?srid=aVb
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*/
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import (
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"fmt"
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"log"
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"math/rand"
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"runtime"
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"strings"
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"time"
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"github.com/go-gl/gl/v2.1/gl"
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"github.com/go-gl/glfw/v3.1/glfw"
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)
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const (
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width = 500
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height = 500
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vertexShaderSource = `
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#version 410
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in vec3 vp;
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void main() {
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gl_Position = vec4(vp, 1.0);
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}
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` + "\x00"
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fragmentShaderSource = `
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#version 410
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out vec4 frag_colour;
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void main() {
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frag_colour = vec4(1, 1, 1, 1);
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}
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` + "\x00"
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rows = 10
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cols = 10
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fps = 10
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threshold = 0.15
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)
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var (
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square = []float32{
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-0.5, 0.5, 0,
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-0.5, -0.5, 0,
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0.5, -0.5, 0,
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-0.5, 0.5, 0,
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0.5, 0.5, 0,
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0.5, -0.5, 0,
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}
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)
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func main() {
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runtime.LockOSThread()
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window := initGlfw()
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defer glfw.Terminate()
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program := initOpenGL()
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cells := makeCells()
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for !window.ShouldClose() {
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t := time.Now()
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for x := range cells {
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for _, c := range cells[x] {
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c.checkState(cells)
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}
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}
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draw(cells, window, program)
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time.Sleep(time.Second/time.Duration(fps) - time.Since(t))
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}
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}
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// initGlfw initializes glfw and returns a Window to use.
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func initGlfw() *glfw.Window {
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if err := glfw.Init(); err != nil {
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panic(err)
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}
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glfw.WindowHint(glfw.Resizable, glfw.False)
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glfw.WindowHint(glfw.ContextVersionMajor, 4)
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glfw.WindowHint(glfw.ContextVersionMinor, 1)
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glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
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glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
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window, err := glfw.CreateWindow(width, height, "Conway's Game of Life", nil, nil)
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if err != nil {
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panic(err)
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}
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window.MakeContextCurrent()
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return window
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}
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// initOpenGL initializes OpenGL and returns an initialized program.
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func initOpenGL() uint32 {
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if err := gl.Init(); err != nil {
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panic(err)
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}
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version := gl.GoStr(gl.GetString(gl.VERSION))
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log.Println("OpenGL version", version)
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vertexShader, err := compileShader(vertexShaderSource, gl.VERTEX_SHADER)
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if err != nil {
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panic(err)
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}
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fragmentShader, err := compileShader(fragmentShaderSource, gl.FRAGMENT_SHADER)
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if err != nil {
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panic(err)
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}
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prog := gl.CreateProgram()
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gl.AttachShader(prog, vertexShader)
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gl.AttachShader(prog, fragmentShader)
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gl.LinkProgram(prog)
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return prog
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}
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func draw(cells [][]*cell, window *glfw.Window, program uint32) {
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gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
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gl.UseProgram(program)
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for x := range cells {
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for _, c := range cells[x] {
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c.draw()
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}
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}
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glfw.PollEvents()
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window.SwapBuffers()
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}
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// makeVao initializes and returns a vertex array from the points provided.
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func makeVao(points []float32) uint32 {
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var vbo uint32
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gl.GenBuffers(1, &vbo)
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gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
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gl.BufferData(gl.ARRAY_BUFFER, 4*len(points), gl.Ptr(points), gl.STATIC_DRAW)
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var vao uint32
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gl.GenVertexArrays(1, &vao)
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gl.BindVertexArray(vao)
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gl.EnableVertexAttribArray(0)
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gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
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gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 0, nil)
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return vao
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}
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func compileShader(source string, shaderType uint32) (uint32, error) {
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shader := gl.CreateShader(shaderType)
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csources, free := gl.Strs(source)
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gl.ShaderSource(shader, 1, csources, nil)
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free()
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gl.CompileShader(shader)
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var status int32
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gl.GetShaderiv(shader, gl.COMPILE_STATUS, &status)
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if status == gl.FALSE {
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var logLength int32
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gl.GetShaderiv(shader, gl.INFO_LOG_LENGTH, &logLength)
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log := strings.Repeat("\x00", int(logLength+1))
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gl.GetShaderInfoLog(shader, logLength, nil, gl.Str(log))
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return 0, fmt.Errorf("failed to compile %v: %v", source, log)
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}
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return shader, nil
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}
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func makeCells() [][]*cell {
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rand.Seed(time.Now().UnixNano())
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cells := make([][]*cell, rows, rows)
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for x := 0; x < rows; x++ {
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for y := 0; y < cols; y++ {
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c := newCell(x, y)
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c.alive = rand.Float64() < threshold
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c.aliveNext = c.alive
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cells[x] = append(cells[x], c)
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}
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}
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return cells
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}
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type cell struct {
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drawable uint32
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alive bool
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aliveNext bool
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x int
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y int
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}
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func newCell(x, y int) *cell {
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points := make([]float32, len(square), len(square))
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copy(points, square)
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for i := 0; i < len(points); i++ {
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var position float32
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var size float32
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switch i % 3 {
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case 0:
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size = 1.0 / float32(cols)
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position = float32(x) * size
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case 1:
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size = 1.0 / float32(rows)
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position = float32(y) * size
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default:
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continue
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}
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if points[i] < 0 {
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points[i] = (position * 2) - 1
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} else {
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points[i] = ((position + size) * 2) - 1
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}
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}
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return &cell{
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drawable: makeVao(points),
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x: x,
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y: y,
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}
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}
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func (c *cell) draw() {
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if !c.alive {
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return
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}
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gl.BindVertexArray(c.drawable)
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gl.DrawArrays(gl.TRIANGLES, 0, int32(len(square)/3))
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}
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// checkState determines the state of the cell for the next tick of the game
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func (c *cell) checkState(cells [][]*cell) {
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c.alive = c.aliveNext
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c.aliveNext = c.alive
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liveCount := c.liveNeighbors(cells)
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if c.alive {
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// 1. Any live cell with fewer than two live neighbours dies, as if caused by underpopulation
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if liveCount < 2 {
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c.alive = false
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}
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// 2. Any live cell with two or three live neighbors lives on to the next generation
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if liveCount == 2 || liveCount == 3 {
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c.aliveNext = true
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}
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// 3. Any live cell with more than three live neighbors dies, as if by overpopulation
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if liveCount > 3 {
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c.aliveNext = false
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}
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} else {
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// 4. Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction
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if liveCount == 3 {
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c.aliveNext = true
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}
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}
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}
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// liveNeighbors returns the number of live neighbors for a cell
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func (c *cell) liveNeighbors(cells [][]*cell) int {
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var liveCount int
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add := func(x, y int) {
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// If we're at an edge, check the other side of the board.
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if x == len(cells) {
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x = 0
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} else if x == -1 {
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x = len(cells) - 1
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}
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if y == len(cells[x]) {
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y = 0
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} else if y == -1 {
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y = len(cells[x]) - 1
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}
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if cells[x][y].alive {
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liveCount++
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}
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}
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add(c.x-1, c.y) // To the left
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add(c.x+1, c.y) // To the right
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add(c.x, c.y+1) // Up
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add(c.x, c.y-1) // Down
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add(c.x-1, c.y+1) // Top-Left
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add(c.x+1, c.y+1) // Top-Right
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add(c.x-1, c.y-1) // Bottom-Left
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add(c.x+1, c.y-1) // Bottom-Right
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return liveCount
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}
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