#232: stop rebuilding the gas vents every frame

GasVentField called queue_redraw() every frame and its _draw rebuilt six
vents of seven glowing polygons each - 168 antialiased polylines
re-tessellated per frame, since every NeonDraw call expands into four.

Measured first: 40 rasterisations over 30 frames, costing 6.6ms against a
32.4ms floor. For scale, the black hole's cached disc costs 0.1ms.

Both halves are pieces now. The sources never move, never recolour and never
fade, so they are rasterised once. The rising bubbles genuinely change size
and opacity, but size is scale and opacity is modulate - neither needs the
geometry rebuilding. 40 rasterisations over 30 frames became 0.

Two things worth recording.

The static extraction alone measured NOTHING - 7.1ms against 6.6ms, inside
the noise. softpipe is a CPU rasteriser: it prices FILL, and cached geometry
fills the same pixels. It cannot see a tessellation saving at all. After the
full change the frame time read NEGATIVE with the floor drifting 28 to 39ms
between runs, so no millisecond figure is claimed here. The rasterisation
count is the reproducible result; what it is worth on a phone is unmeasured.

And scaling a NeonPiece scales its STROKE with it. The bubbles were first
built as unit circles scaled up by their radius, which multiplied NeonDraw's
widths by five to fourteen - a hundred pixels of glow around a fourteen
pixel bubble. They rendered as bright blobs, the rasterisation count said
40 -> 0, and only the screenshot disagreed. Built at the largest radius and
scaled DOWN now, so the stroke only ever thins. The trap is noted at the
call site: scale is safe for moving and shrinking a piece and quietly wrong
for growing one.

NeonPiece.add_polygon gained a width, which it needed to keep the vents'
authored stroke rather than silently fattening them.

179/179.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019AJMdB7iuHuLFZM1aBu3GD

surface/GasVentField.gd

@@ -9,7 +9,23 @@ const RESOURCE_PICKUP_VFX = preload("res://vfx/ResourcePickupVFX.gd")
 
 @export var fleet_path: NodePath = NodePath("../Fleet")
 @onready var fleet: Node2D = get_node(fleet_path)
+const SOURCE_COLOUR: Color = Color(0.85, 0.52, 1.0)
+const CORE_COLOUR: Color = Color(0.15, 0.03, 0.22)
+# Offsets from a vent's centre, and each bubble's radius.
+const SOURCE_BUBBLES: Array = [
+	[Vector2(-20.0, 8.0), 20.0],
+	[Vector2(18.0, 14.0), 27.0],
+	[Vector2(17.0, -22.0), 15.0],
+]
+
+const BUBBLES_PER_VENT: int = 4
+const BUBBLE_MIN_RADIUS: float = 5.0
+const BUBBLE_MAX_RADIUS: float = 14.0
+const EMISSION_COLOUR: Color = Color(0.92, 0.68, 1.0)
+
 var vents: Array[Vector2] = []
+# One row of rising-bubble pieces per vent.
+var bubbles: Array = []
 var progress: float = 0.0
 var emission_phase: float = 0.0
 func _ready() -> void:
@@ -24,10 +40,73 @@ func _ready() -> void:
 	var rng := RandomNumberGenerator.new()
 	rng.seed = hash(GameState.planet_id if GameState.planet_id != "" else GameState.planet_name)
 	for i in range(6): vents.append(Vector2(rng.randf_range(-800,800), rng.randf_range(-650,650)))
-	queue_redraw()
+	_build_sources()
+	_build_bubbles()
+	_place_bubbles()
+
+
+# The sources never move, never change colour and never fade - they were
+# simply being re-tessellated every frame alongside the bubbles rising out of
+# them, because one _draw() covered both. Eighteen glowing polygons a frame,
+# each of which NeonDraw expands into four antialiased polylines. Rasterised
+# once into a piece each now, per the rule issues #6 and #10 set.
+func _build_sources() -> void:
+	for vent in vents:
+		var piece: NeonPiece = NeonPiece.create(self, vent, SOURCE_COLOUR)
+		piece.core_color = CORE_COLOUR
+		piece.z_index = -1
+		for bubble in SOURCE_BUBBLES:
+			var ring := PackedVector2Array()
+			for i in range(12):
+				var angle: float = TAU * float(i) / 12.0
+				ring.append(Vector2(bubble[0]) + Vector2(cos(angle), sin(angle)) * float(bubble[1]))
+			piece.add_polygon(ring, 0.9, 0.6)
+
+
+# One piece per rising bubble, built as a UNIT circle and thereafter only
+# moved, scaled and faded. The bubble genuinely changes size and opacity as
+# it climbs, which is why this used to redraw - but size is scale and opacity
+# is modulate, and neither needs the geometry rebuilding.
+func _build_bubbles() -> void:
+	for vent in vents:
+		var row: Array = []
+		for i in range(BUBBLES_PER_VENT):
+			var piece: NeonPiece = NeonPiece.create(self, vent, EMISSION_COLOUR)
+			piece.core_color = CORE_COLOUR
+			piece.z_index = -1
+			# Built at the LARGEST size a bubble reaches and scaled DOWN,
+			# never up. Scaling a piece scales its stroke with it, and a unit
+			# circle blown up to radius 14 took NeonDraw's widths with it -
+			# a hundred pixels of glow around a fourteen pixel bubble, which
+			# rendered as a bright blob rather than a bubble. Downward, the
+			# stroke only ever thins, which is what a smaller bubble wants.
+			var ring := PackedVector2Array()
+			for point in range(10):
+				var angle: float = TAU * float(point) / 10.0
+				ring.append(Vector2(cos(angle), sin(angle)) * BUBBLE_MAX_RADIUS)
+			piece.add_polygon(ring, 0.75, 0.45)
+			row.append(piece)
+		bubbles.append(row)
+
+
+# Where one bubble sits, how big it is and how faded, for a point in its
+# climb. Unchanged arithmetic - only the thing it is applied to changed.
+func _place_bubbles() -> void:
+	for v in range(vents.size()):
+		for i in range(BUBBLES_PER_VENT):
+			var travel: float = fmod(emission_phase + float(i) * 0.25, 1.0)
+			var piece: NeonPiece = bubbles[v][i]
+			piece.position = vents[v] + Vector2(
+				sin((travel + float(i)) * TAU) * 11.0,
+				-48.0 - travel * 92.0)
+			var radius: float = lerpf(BUBBLE_MIN_RADIUS, BUBBLE_MAX_RADIUS, travel)
+			var k: float = radius / BUBBLE_MAX_RADIUS
+			piece.scale = Vector2(k, k)
+			piece.modulate.a = 1.0 - travel * 0.72
 func _process(delta: float) -> void:
 	emission_phase = fmod(emission_phase + delta * 0.55, 1.0)
-	queue_redraw()
+	# Node properties only. Nothing is rasterised after the first frame.
+	_place_bubbles()
 	for vent in vents:
 		if fleet.get_centroid().distance_to(vent) < 90.0:
 			progress += delta
@@ -42,43 +121,3 @@ func _process(delta: float) -> void:
 					to_global(vent), GameState.RESOURCE_GAS, taken)
 			return
 	progress = 0.0
-func _draw() -> void:
-	for vent in vents:
-		_draw_gas_source(vent)
-		_draw_emission(vent)
-
-
-func _draw_gas_source(centre: Vector2) -> void:
-	var colour := Color(0.85, 0.52, 1.0)
-	var core := Color(0.15, 0.03, 0.22)
-	var bubbles: Array = [
-		[centre + Vector2(-20.0, 8.0), 20.0],
-		[centre + Vector2(18.0, 14.0), 27.0],
-		[centre + Vector2(17.0, -22.0), 15.0],
-	]
-	for bubble in bubbles:
-		var ring := PackedVector2Array()
-		for i in range(12):
-			var angle: float = TAU * float(i) / 12.0
-			ring.append(bubble[0] + Vector2(cos(angle), sin(angle)) * float(bubble[1]))
-		NeonDraw.draw_glowing_polygon(self, ring, colour, 0.9, core, 0.6)
-
-
-func _draw_emission(centre: Vector2) -> void:
-	# Small bubbles continuously rise out of every source. This remains
-	# animated even when the fleet is not collecting, so the vent reads as
-	# an active gas generator rather than a static decoration.
-	var core := Color(0.15, 0.03, 0.22)
-	for i in range(4):
-		var travel: float = fmod(emission_phase + float(i) * 0.25, 1.0)
-		var bubble_centre := centre + Vector2(
-			sin((travel + float(i)) * TAU) * 11.0,
-			-48.0 - travel * 92.0
-		)
-		var radius: float = lerpf(5.0, 14.0, travel)
-		var colour := Color(0.92, 0.68, 1.0, 1.0 - travel * 0.72)
-		var ring := PackedVector2Array()
-		for point in range(10):
-			var angle: float = TAU * float(point) / 10.0
-			ring.append(bubble_centre + Vector2(cos(angle), sin(angle)) * radius)
-		NeonDraw.draw_glowing_polygon(self, ring, colour, 0.75, core, 0.45)

vfx/NeonPiece.gd

@@ -34,8 +34,9 @@ static func create(parent: Node, at: Vector2, colour: Color, alpha: float = 1.0)
 	return piece
 
 
-func add_polygon(points: PackedVector2Array, piece_pulse: float = 1.0) -> void:
+func add_polygon(points: PackedVector2Array, piece_pulse: float = 1.0,
-	polygons.append({"points": points, "pulse": piece_pulse})
+		width: float = 1.0) -> void:
+	polygons.append({"points": points, "pulse": piece_pulse, "width": width})
 
 
 func add_path(points: PackedVector2Array, piece_pulse: float = 1.0,
@@ -49,7 +50,8 @@ func add_line(from: Vector2, to: Vector2, width: float, piece_pulse: float = 1.0
 
 func _draw() -> void:
 	for poly in polygons:
-		NeonDraw.draw_glowing_polygon(self, poly.points, glow_color, poly.pulse * pulse, core_color)
+		NeonDraw.draw_glowing_polygon(self, poly.points, glow_color,
+			poly.pulse * pulse, core_color, float(poly.get("width", 1.0)))
 	for path in paths:
 		NeonDraw.draw_glowing_path(self, path.points, glow_color,
 			path.pulse * pulse, path.width, core_color)