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

	currentMove  mgl32.Vec3
	currentLook  mgl32.Vec2
	lastMousePos mgl32.Vec2

	view mgl32.Mat4

	lastTime float64
}

var instance *FPSControls

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

	deltaTime := time - c.lastTime
	c.lastTime = time

	forward, right, up := c.directions()

	globalUp := mgl32.Vec3{0, 1, 0}
	move := right.Mul(c.currentMove.X()).Add(globalUp.Mul(c.currentMove.Y())).Add(forward.Mul(c.currentMove.Z()))
	c.position = c.position.Add(move.Mul(float32(deltaTime) * c.moveSpeed))

	c.rotation = c.rotation.Add(c.currentLook.Mul(float32(deltaTime) * c.lookSpeed))
	c.currentLook = mgl32.Vec2{}
	c.view = mgl32.LookAtV(c.position, c.position.Add(forward), up)

}

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.SetKeyCallback(func(window *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
		var val float32

		switch action {
		case glfw.Repeat:
			return
		case glfw.Press:
			val = 1
		case glfw.Release:
			val = 0
		}

		switch key {
		case glfw.KeyW:
			instance.currentMove[2] = val
		case glfw.KeyS:
			instance.currentMove[2] = -val
		case glfw.KeyA:
			instance.currentMove[0] = val
		case glfw.KeyD:
			instance.currentMove[0] = -val
		case glfw.KeySpace:
			instance.currentMove[1] = val
		case glfw.KeyLeftShift:
			instance.currentMove[1] = -val
		}
	})

	window.SetCursorPosCallback(func(window *glfw.Window, y float64, x float64) {
		pos := mgl32.Vec2{float32(x), float32(y)}
		instance.currentLook = instance.lastMousePos.Sub(pos)
		instance.currentLook[0] *= -1
		instance.lastMousePos = pos
	})

	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
}