opengl-deferred/utils/fpscontrols/fpscontrols.go

package fpscontrols

import (
	"math"

	"github.com/go-gl/glfw/v3.3/glfw"
	"github.com/go-gl/mathgl/mgl32"
)

type FPSControls struct {
	lookSpeed float32
	moveSpeed float32

	position mgl32.Vec3
	rotation mgl32.Vec2

	lastMousePos mgl32.Vec2

	view mgl32.Mat4

	window *glfw.Window

	lastTime float64
}

var instance *FPSControls

func (c *FPSControls) Update() {
	time := glfw.GetTime()

	var deltaTime float32 = float32(time - c.lastTime)
	c.lastTime = time

	_, right, _ := c.directions()
	globalUp := mgl32.Vec3{0, 1, 0}

	move := mgl32.Vec3{0, 0, 0}

	if c.window.GetKey(glfw.KeyA) == glfw.Press {
		move[0] += 1
	}
	if c.window.GetKey(glfw.KeyD) == glfw.Press {
		move[0] -= 1
	}

	if c.window.GetKey(glfw.KeySpace) == glfw.Press {
		move[1] += 1
	}
	if c.window.GetKey(glfw.KeyLeftShift) == glfw.Press {
		move[1] -= 1
	}

	if c.window.GetKey(glfw.KeyW) == glfw.Press {
		move[2] += 1
	}
	if c.window.GetKey(glfw.KeyS) == glfw.Press {
		move[2] -= 1
	}

	move = right.Mul(move.X()).Add(globalUp.Mul(move.Y())).Add(right.Cross(globalUp).Mul(move.Z()))
	c.position = c.position.Add(move.Mul(deltaTime * c.moveSpeed))

	x, y := c.window.GetCursorPos()
	look := mgl32.Vec2{
		float32(y) - c.lastMousePos.X(),
		c.lastMousePos.Y() - float32(x),
	}.Mul(deltaTime * c.lookSpeed)

	c.rotation = c.rotation.Add(look)
	c.rotation = mgl32.Vec2{
		min(max(-89.9, c.rotation.X()), 89.9),
		float32(int32(c.rotation.Y())%360) + c.rotation.Y() - float32(int32(c.rotation.Y())),
	}
	c.lastMousePos[0] = float32(y)
	c.lastMousePos[1] = float32(x)

	forward, _, _ := c.directions()
	c.view = mgl32.LookAtV(c.position, c.position.Add(forward), globalUp)
}

func Get(lookSpeed, moveSpeed float32, position mgl32.Vec3, rotation mgl32.Vec2, window *glfw.Window) *FPSControls {
	if instance != nil {
		return instance
	}

	instance = &FPSControls{
		moveSpeed: moveSpeed,
		lookSpeed: lookSpeed,
		position:  position,
		rotation:  rotation,
		window:    window,
	}

	window.SetInputMode(glfw.CursorMode, glfw.CursorDisabled)

	return instance
}

func (c *FPSControls) directions() (mgl32.Vec3, mgl32.Vec3, mgl32.Vec3) {
	rad := mgl32.Vec2{
		mgl32.DegToRad(c.rotation.X()),
		mgl32.DegToRad(c.rotation.Y()),
	}

	sin := mgl32.Vec2{
		float32(math.Sin(float64(rad.X()))),
		float32(math.Sin(float64(rad.Y()))),
	}

	cos := mgl32.Vec2{
		float32(math.Cos(float64(rad.X()))),
		float32(math.Cos(float64(rad.Y()))),
	}

	forward := mgl32.Vec3{
		cos.X() * sin.Y(),
		-sin.X(),
		cos.X() * cos.Y(),
	}

	right := mgl32.Vec3{
		cos.Y(),
		0,
		-sin.Y(),
	}

	up := forward.Cross(right)

	return forward, right, up
}

func (c *FPSControls) View() mgl32.Mat4 {
	return c.view
}

func (c *FPSControls) Position() mgl32.Vec3 {
	return c.position
}

func (c *FPSControls) Rotation() mgl32.Vec2 {
	return c.rotation
}