spaceship/vfx/NeonPiece.gd

class_name NeonPiece
extends Node2D

# One movable piece of neon art, rasterised ONCE and thereafter animated
# only through node properties.
#
# Godot re-runs _draw() solely when a redraw is requested; changing
# position/rotation/scale/modulate/visible reuses the cached geometry
# instead. Since every NeonDraw call expands into four antialiased
# polylines, redrawing a shape each frame just to move or fade it is the
# expensive way to do the cheapest kind of animation. Ship.gd and
# Asteroid.gd already work this way - this is the same idea packaged so a
# building can be assembled out of independently movable parts.
#
# Geometry is defined in local space around the piece's own origin, so the
# owner can move, spin, scale and fade it without touching the shape.

var polygons: Array = []
# Open runs of points, as distinct from `polygons`, which close. An accretion
# disc is arcs, not rings, so it needs the open form to be a piece at all.
var paths: Array = []
var lines: Array = []
var glow_color: Color = Color.WHITE
var core_color: Color = NeonDraw.DEFAULT_CORE
var pulse: float = 1.0


static func create(parent: Node, at: Vector2, colour: Color, alpha: float = 1.0) -> NeonPiece:
	var piece: NeonPiece = NeonPiece.new()
	piece.position = at
	piece.glow_color = colour
	piece.modulate.a = alpha
	parent.add_child(piece)
	return piece


func add_polygon(points: PackedVector2Array, piece_pulse: float = 1.0) -> void:
	polygons.append({"points": points, "pulse": piece_pulse})


func add_path(points: PackedVector2Array, piece_pulse: float = 1.0,
		width: float = 1.0) -> void:
	paths.append({"points": points, "pulse": piece_pulse, "width": width})


func add_line(from: Vector2, to: Vector2, width: float, piece_pulse: float = 1.0) -> void:
	lines.append({"from": from, "to": to, "width": width, "pulse": piece_pulse})


func _draw() -> void:
	for poly in polygons:
		NeonDraw.draw_glowing_polygon(self, poly.points, glow_color, poly.pulse * pulse, core_color)
	for path in paths:
		NeonDraw.draw_glowing_path(self, path.points, glow_color,
			path.pulse * pulse, path.width, core_color)
	for line in lines:
		NeonDraw.draw_glowing_line(self, line.from, line.to, glow_color,
			line.pulse * pulse, line.width, core_color)