curve.gd

extends Node2D
tool


# Declare member variables here. Examples:
# var a = 2
# var b = "text"

onready var marker = $line
var curve = Curve2D.new()

# Called when the node enters the scene tree for the first time.
func _ready():	
	create_path(curve)

func create_path(crv:Curve2D):
	crv.clear_points()
	var next_point = Vector2.ZERO
	crv.add_point(next_point)
	next_point = self.add_straight(crv, next_point, 50)
	next_point = self.add_loop(crv, next_point, 50)
	next_point = self.add_straight(crv, next_point, 50)
	next_point = self.add_loop(crv, next_point, 100)
	next_point = self.add_straight(crv, next_point, 50)

func add_straight(crv:Curve2D, next_point:Vector2, length):
	next_point = next_point + Vector2.RIGHT * length
	crv.add_point(next_point)
	return next_point

func add_loop(crv:Curve2D, next_point:Vector2, s):
	var c = 0.551915024494 * s  # ~MAGIC~ -> https://spencermortensen.com/articles/bezier-circle/
	crv.add_point(next_point + Vector2(2*s, 0), Vector2.ZERO, Vector2(c, 0))
	crv.add_point(next_point + Vector2(3*s, -s), Vector2(0, c), Vector2(0, -c))
	crv.add_point(next_point + Vector2(2*s, -2*s), Vector2(c, 0), Vector2(-c, 0))
	crv.add_point(next_point + Vector2(s, -s), Vector2(0, -c), Vector2(0, c))
	crv.add_point(next_point + Vector2(2*s, 0), Vector2(-c, 0))
	crv.add_point(next_point + Vector2(4*s, 0))
	return next_point + Vector2(4*s, 0)

var t = 0.0
func _process(delta):
	t += delta * 0.1
	if t > 1:
		t = 0.0	
	position = -curve.interpolate_baked(t * curve.get_baked_length(), true)
	

func _draw():
	var points:PoolVector2Array = curve.tessellate ()

	var p1 = points[0]
	for idx in range(1, len(points)):
		var p2 = points[idx]
		draw_line(p1, p2, Color.aliceblue, 4, true)
		p1 = p2