func main() {
// Initialize GLFW for window management
glfw.SetErrorCallback(glfwErrorCallback)
if !glfw.Init() {
panic("failed to initialize glfw")
}
defer glfw.Terminate()
glfw.WindowHint(glfw.Resizable, glfw.False)
glfw.WindowHint(glfw.ContextVersionMajor, 3)
glfw.WindowHint(glfw.ContextVersionMinor, 3)
glfw.WindowHint(glfw.OpenglForwardCompatible, glfw.True) // Necessary for OS X
glfw.WindowHint(glfw.OpenglProfile, glfw.OpenglCoreProfile) // Necessary for OS X
glfw.WindowHint(glfw.OpenglDebugContext, 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)
}
// Note that it is possible to use GL functions spanning multiple versions
if err := gl4.Init(); err != nil {
fmt.Printf("Could not initialize GL 4.4 (non-fatal)")
}
if gl.ARB_debug_output {
gl.Enable(gl.DEBUG_OUTPUT_SYNCHRONOUS_ARB)
gl.DebugMessageCallbackARB(gl.DebugProc(glDebugCallback), gl.Ptr(nil))
// Trigger an error to demonstrate debug output
gl.Enable(gl.CONTEXT_FLAGS)
}
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(70.0, 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)
gl.ActiveTexture(gl.TEXTURE0)
gl.BindTexture(gl.TEXTURE_2D, texture)
gl.DrawArrays(gl.TRIANGLES, 0, 6*2*3)
// Maintenance
window.SwapBuffers()
glfw.PollEvents()
}
}
func newProgram(vertexShaderSource, fragmentShaderSource string) (uint32, error) {
vertexShader, err := compileShader(vertexShaderSource, gl.VERTEX_SHADER)
if err != nil {
return 0, err
}
fragmentShader, err := compileShader(fragmentShaderSource, gl.FRAGMENT_SHADER)
if err != nil {
return 0, err
}
program := gl.CreateProgram()
gl.AttachShader(program, vertexShader)
gl.AttachShader(program, fragmentShader)
gl.LinkProgram(program)
var status int32
gl.GetProgramiv(program, gl.LINK_STATUS, &status)
if status == gl.FALSE {
var logLength int32
gl.GetProgramiv(program, gl.INFO_LOG_LENGTH, &logLength)
log := strings.Repeat("\x00", int(logLength+1))
gl.GetProgramInfoLog(program, logLength, nil, gl.Str(log))
return 0, errors.New(fmt.Sprintf("failed to link program: %v", log))
}
gl.DeleteShader(vertexShader)
gl.DeleteShader(fragmentShader)
return program, nil
}
func GetUniformLocation(shaderName, uniformName string) (int32, error) {
prog, ok := shader_progs[shaderName]
if !ok {
return -1, fmt.Errorf("No shader named '%s'", shaderName)
}
return gl.GetUniformLocation(prog, gl.Str(fmt.Sprintf("%s\x00", uniformName))), nil
}
func compileShader(source string, shaderType uint32) (uint32, error) {
shader := gl.CreateShader(shaderType)
csource := gl.Str(source)
gl.ShaderSource(shader, 1, &csource, nil)
gl.CompileShader(shader)
var status int32
gl.GetShaderiv(shader, gl.COMPILE_STATUS, &status)
if status == gl.FALSE {
var logLength int32
gl.GetShaderiv(shader, gl.INFO_LOG_LENGTH, &logLength)
log := strings.Repeat("\x00", int(logLength+1))
gl.GetShaderInfoLog(shader, logLength, nil, gl.Str(log))
return 0, fmt.Errorf("failed to compile %v: %v", source, log)
}
return shader, nil
}