extends MeshInstance3D

var mat: StandardMaterial3D
var ang: float = 0.0
var poslist: PackedVector3Array = PackedVector3Array()

func _ready():
	mat = StandardMaterial3D.new()
	mat.albedo_color = Color(1, 1, 1, 0.25)
	mat.cull_mode = BaseMaterial3D.CULL_DISABLED
	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
	mat.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
	
	mesh = ImmediateMesh.new()
	
	var n = 30
	for i in range(0, n, 1):
		poslist.append(Vector3.ZERO)


func _process(delta):
	# store positon to PackedVector3Array
	for i in range(0, poslist.size(), 1):
		var x1 = -12.0 + 4.0 * sin(deg_to_rad((ang + 10 * i) * 0.75))
		var y1 = 4.0 + 4.0 * sin(deg_to_rad(ang + 10 * i))
		var z1 = 10 - 1.0 * i
		poslist[i] = Vector3(x1, y1, z1)

	# set ImmediateMesh
	mesh.clear_surfaces()
	mesh.surface_begin(Mesh.PRIMITIVE_TRIANGLES, mat)
	# mesh.surface_set_color(Color.WHITE)

	var r = 0.5
	for i in range(0, poslist.size() - 2, 1):
		var p0 = get_rect_pos(poslist[i], poslist[i+1], r)
		var p1 = get_rect_pos(poslist[i+1], poslist[i+2], r)
		mesh.surface_add_vertex(p0[3])
		mesh.surface_add_vertex(p0[0])
		mesh.surface_add_vertex(p1[3])
		mesh.surface_add_vertex(p1[3])
		mesh.surface_add_vertex(p0[0])
		mesh.surface_add_vertex(p1[0])
	
		mesh.surface_add_vertex(p0[0])
		mesh.surface_add_vertex(p0[2])
		mesh.surface_add_vertex(p1[0])
		mesh.surface_add_vertex(p1[0])
		mesh.surface_add_vertex(p0[2])
		mesh.surface_add_vertex(p1[2])
	
		mesh.surface_add_vertex(p0[2])
		mesh.surface_add_vertex(p0[1])
		mesh.surface_add_vertex(p1[2])
		mesh.surface_add_vertex(p1[2])
		mesh.surface_add_vertex(p0[1])
		mesh.surface_add_vertex(p1[1])
	
		mesh.surface_add_vertex(p0[1])
		mesh.surface_add_vertex(p0[3])
		mesh.surface_add_vertex(p1[1])
		mesh.surface_add_vertex(p1[1])
		mesh.surface_add_vertex(p0[3])
		mesh.surface_add_vertex(p1[3])
	
	mesh.surface_end()
	
	ang += 120.0 * delta

func get_rect_pos(v0: Vector3, v1: Vector3, r: float):
	var v = v1 - v0
	var va = v.cross(Vector3.UP).normalized()
	var vb = v.cross(va).normalized()
	var pv0 = v0 + r * vb
	var pv1 = v0 - r * vb
	var pv2 = v0 + r * va
	var pv3 = v0 - r * va
	return [pv0, pv1, pv2, pv3]