fix river water direction2

core/biome_generator/biome_generator.gd

@@ -8,6 +8,19 @@ const CHUNK_GENERATION_STEPS_PER_FRAME: int = 2
 const CHUNK_CLEANUP_STEPS_PER_FRAME: int = 4
 const LAMPPOST_WIRE_STEPS_PER_FRAME: int = 1
 const RAILWAY_SCENE_DIRECTORY: String = "res://tgcc/chunk/railway/scene"
+const RIVER_SIDE_ORDER: Array[String] = ["north", "est", "south", "west"]
+const RIVER_DIRECTIONS: Dictionary = {
+	"north": Vector2(0.0, -1.0),
+	"est": Vector2(1.0, 0.0),
+	"south": Vector2(0.0, 1.0),
+	"west": Vector2(-1.0, 0.0),
+}
+const RIVER_NEIGHBOUR_OFFSETS: Dictionary = {
+	"north": Vector2i(0, -1),
+	"est": Vector2i(1, 0),
+	"south": Vector2i(0, 1),
+	"west": Vector2i(-1, 0),
+}
 
 @export_group("Rails")
 @export var rail_path: Path3D 
@@ -616,11 +629,15 @@ func _add_compatible_biome(grid_pos: Vector2i) -> void:
 		var have_lamppost = false
 		if info_new != null and "have_lamppost" in info_new:
 			have_lamppost = info_new.have_lamppost
+
+		var river_flow_direction = _calculate_river_flow_direction(grid_pos, choise.data["river_connections"])
+		_apply_river_flow_direction(new_chunk, river_flow_direction)
 			
 		board[grid_pos] = {
 			"type": "bioma", 
 			"exit": choise.data["connections"], 
 			"river_exit": choise.data["river_connections"],
+			"river_flow_direction": river_flow_direction,
 			"heights": choise.data["heights"], 
 			"node": new_chunk, 
 			"info": info_new,
@@ -647,12 +664,109 @@ func _add_compatible_biome(grid_pos: Vector2i) -> void:
 			"type": "biome", 
 			"exit": {"north":false, "est":false, "south":false, "west":false}, 
 			"river_exit": {"north":false, "est":false, "south":false, "west":false},
+			"river_flow_direction": Vector2.ZERO,
 			"heights": safe_heights, 
 			"node": backup,
 			"info": info_backup,
 			"have_lamppost": false
 		}
 
+func _calculate_river_flow_direction(grid_pos: Vector2i, river_connections: Dictionary) -> Vector2:
+	var connected_sides: Array[String] = []
+	for side in RIVER_SIDE_ORDER:
+		if river_connections.has(side) and river_connections[side]:
+			connected_sides.append(side)
+
+	if connected_sides.is_empty():
+		return Vector2.ZERO
+
+	var neighbour_flow = _get_connected_neighbour_river_flow(grid_pos, connected_sides)
+	if not neighbour_flow.is_zero_approx():
+		var continued_flow = _continue_river_flow_from_neighbour(grid_pos, connected_sides, neighbour_flow)
+		if not continued_flow.is_zero_approx():
+			return continued_flow.normalized()
+
+	var default_flow = _get_default_river_flow(connected_sides)
+	if default_flow.is_zero_approx():
+		return Vector2.ZERO
+	return default_flow.normalized()
+
+func _get_connected_neighbour_river_flow(grid_pos: Vector2i, connected_sides: Array[String]) -> Vector2:
+	for side in connected_sides:
+		var neighbour_pos: Vector2i = grid_pos + RIVER_NEIGHBOUR_OFFSETS[side]
+		if not board.has(neighbour_pos):
+			continue
+		var neighbour = board[neighbour_pos]
+		if not neighbour.has("river_flow_direction"):
+			continue
+		var neighbour_flow: Vector2 = neighbour["river_flow_direction"]
+		if not neighbour_flow.is_zero_approx():
+			return neighbour_flow.normalized()
+	return Vector2.ZERO
+
+func _continue_river_flow_from_neighbour(grid_pos: Vector2i, connected_sides: Array[String], neighbour_flow: Vector2) -> Vector2:
+	for side in connected_sides:
+		var neighbour_pos: Vector2i = grid_pos + RIVER_NEIGHBOUR_OFFSETS[side]
+		if not board.has(neighbour_pos):
+			continue
+		var neighbour = board[neighbour_pos]
+		if not neighbour.has("river_flow_direction"):
+			continue
+		var side_direction: Vector2 = RIVER_DIRECTIONS[side]
+		var neighbour_direction: Vector2 = neighbour["river_flow_direction"]
+		if neighbour_direction.is_zero_approx():
+			continue
+		neighbour_direction = neighbour_direction.normalized()
+		var other_sides = connected_sides.duplicate()
+		other_sides.erase(side)
+		if other_sides.is_empty():
+			return neighbour_direction
+
+		var other_direction = _get_average_river_side_direction(other_sides)
+		if neighbour_direction.dot(-side_direction) > 0.25:
+			return other_direction - side_direction
+		if neighbour_direction.dot(side_direction) > 0.25:
+			return side_direction - other_direction
+
+	var default_flow = _get_default_river_flow(connected_sides)
+	if default_flow.dot(neighbour_flow) < 0.0:
+		return -default_flow
+	return default_flow
+
+func _get_default_river_flow(connected_sides: Array[String]) -> Vector2:
+	if connected_sides.size() == 1:
+		return RIVER_DIRECTIONS[connected_sides[0]]
+
+	if connected_sides.has("north") and connected_sides.has("south"):
+		return Vector2(0.0, 1.0)
+	if connected_sides.has("est") and connected_sides.has("west"):
+		return Vector2(1.0, 0.0)
+
+	var start_direction: Vector2 = RIVER_DIRECTIONS[connected_sides[0]]
+	var end_direction = _get_average_river_side_direction(connected_sides.slice(1))
+	return end_direction - start_direction
+
+func _get_average_river_side_direction(sides: Array[String]) -> Vector2:
+	var direction := Vector2.ZERO
+	for side in sides:
+		direction += RIVER_DIRECTIONS[side]
+	if direction.is_zero_approx():
+		return Vector2.ZERO
+	return direction / float(sides.size())
+
+func _apply_river_flow_direction(root: Node, flow_direction: Vector2) -> void:
+	if flow_direction.is_zero_approx():
+		return
+	_set_river_flow_direction_recursive(root, flow_direction.normalized())
+
+func _set_river_flow_direction_recursive(node: Node, flow_direction: Vector2) -> void:
+	if node is MeshInstance3D and node.name.begins_with("Water_F"):
+		var mesh_instance := node as MeshInstance3D
+		mesh_instance.set_instance_shader_parameter("river_flow_direction", flow_direction)
+
+	for child in node.get_children():
+		_set_river_flow_direction_recursive(child, flow_direction)
+
 func _needed_connection(near_pos: Vector2i, side_needed: String) -> int:
 	if not board.has(near_pos): 
 		_register_cell_with_ray(near_pos)