feat(foliage): add recovering grass trails and bush contact

world/jajce/FoliageTrailMap.gd

@@ -0,0 +1,98 @@
+class_name FoliageTrailMap
+extends RefCounted
+## Disposable, camera-local footprint field. No per-blade nodes or physics.
+## RG = weighted bend direction, B = pressure, A = weighted actor foot height.
+
+const RESOLUTION := 128
+const CELL_SIZE := 0.5
+const WORLD_SIZE := RESOLUTION * CELL_SIZE
+const TRAIL_RADIUS := 0.95
+const RECOVERY_SECONDS := 8.0
+const MAX_SEGMENT_LENGTH := 3.0
+
+var texture: ImageTexture
+var world_rect := Vector4.ZERO
+
+var _image: Image
+var _origin := Vector2i.ZERO
+var _cells: Dictionary[Vector2i, Color] = {}
+var _previous_positions: Dictionary[int, Vector3] = {}
+
+
+func _init() -> void:
+	_image = Image.create(RESOLUTION, RESOLUTION, false, Image.FORMAT_RGBAF)
+	_image.fill(Color(0, 0, 0, 0))
+	texture = ImageTexture.create_from_image(_image)
+
+
+func clear() -> void:
+	_cells.clear()
+	_previous_positions.clear()
+	_image.fill(Color(0, 0, 0, 0))
+	texture.update(_image)
+
+
+func advance(delta: float, center: Vector3, positions: Dictionary[int, Vector3]) -> void:
+	var next_origin := _world_cell(Vector2(center.x, center.z)) - Vector2i.ONE * (RESOLUTION / 2)
+	var dirty := not _cells.is_empty() or next_origin != _origin
+	_origin = next_origin
+	world_rect = Vector4(_origin.x * CELL_SIZE, _origin.y * CELL_SIZE, WORLD_SIZE, WORLD_SIZE)
+	_decay_and_clip(maxf(delta, 0.0))
+	for actor_id in positions:
+		var end := positions[actor_id]
+		var start: Vector3 = _previous_positions.get(actor_id, end)
+		# A load, teleport, spawn, or skipped actor must never draw a connecting scar.
+		if start.distance_to(end) > MAX_SEGMENT_LENGTH or delta > 0.5:
+			start = end
+		_stamp_segment(start, end)
+	_previous_positions = positions.duplicate()
+	if not dirty and _cells.is_empty():
+		return
+	_image.fill(Color(0, 0, 0, 0))
+	for cell in _cells:
+		var pixel := cell - _origin
+		_image.set_pixelv(pixel, _cells[cell])
+	texture.update(_image)
+
+
+func _decay_and_clip(delta: float) -> void:
+	for cell in _cells.keys():
+		var value := _cells[cell]
+		var pressure := maxf(0.0, value.b - delta / RECOVERY_SECONDS)
+		if pressure <= 0.001 or not _contains(cell):
+			_cells.erase(cell)
+		else:
+			_cells[cell] = value * (pressure / value.b)
+
+
+func _stamp_segment(start: Vector3, end: Vector3) -> void:
+	var a := Vector2(start.x, start.z)
+	var b := Vector2(end.x, end.z)
+	var line := b - a
+	var length_squared := line.length_squared()
+	var radius := Vector2.ONE * TRAIL_RADIUS
+	var first := _world_cell(a.min(b) - radius).max(_origin)
+	var last := _world_cell(a.max(b) + radius).min(_origin + Vector2i.ONE * (RESOLUTION - 1))
+	for y in range(first.y, last.y + 1):
+		for x in range(first.x, last.x + 1):
+			var cell := Vector2i(x, y)
+			var point := (Vector2(cell) + Vector2.ONE * 0.5) * CELL_SIZE
+			var along := clampf((point - a).dot(line) / maxf(length_squared, 0.0001), 0.0, 1.0)
+			var offset := point - a - line * along
+			var pressure := 1.0 - smoothstep(0.16, TRAIL_RADIUS, offset.length())
+			var existing: Color = _cells.get(cell, Color(0, 0, 0, 0))
+			if pressure <= 0.001 or pressure < existing.b:
+				continue
+			# A swept capsule parts blades to both sides of the travelled line.
+			var away := offset.normalized()
+			var height := lerpf(start.y, end.y, along)
+			_cells[cell] = Color(away.x, away.y, 1.0, height) * pressure
+
+
+func _world_cell(position: Vector2) -> Vector2i:
+	return Vector2i(floori(position.x / CELL_SIZE), floori(position.y / CELL_SIZE))
+
+
+func _contains(cell: Vector2i) -> bool:
+	var pixel := cell - _origin
+	return pixel.x >= 0 and pixel.y >= 0 and pixel.x < RESOLUTION and pixel.y < RESOLUTION