106 lines
3.2 KiB
GDScript3
106 lines
3.2 KiB
GDScript3
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class_name LineTrail2D
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extends Line2D
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## Leave a trail behind this node.
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@export var tracking: Node2D
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## Minimum distance before adding a new point to the trail line.
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## 0 = always add a new point on each frame.
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@export var min_distance: float = 1.
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## Maximum length of the trail before starting to trim.
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## 0 = no length limit.
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@export var max_length: float = 0.
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## Maximum lifetime of the trail (in seconds) before starting to trim.
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## 0 = no lifetime limit.
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@export var max_lifetime: float = 3.
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# Each index represents the remaining time in seconds before each point is
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# removed from the line, starting to count after the previous point is removed.
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# As an example: [1, 2, 2] means that the first point will be removed in 1
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# second; the second point 2 seconds after the first (so 3 seconds from now);
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# and the third point 2 seconds after the second (so 5 seconds from now).
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var _points_life := PackedFloat32Array()
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func _ready() -> void:
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clear_points()
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func _process(delta: float) -> void:
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global_transform = Transform2D.IDENTITY
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var new_position := tracking.global_position
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# Add new points.
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var maybe_exceeds_max_length := false
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if _points_life.size() == 0:
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_add_point(new_position)
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else:
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var last_point := get_point_position(_points_life.size() - 1)
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var distance_sqr := (new_position - last_point).length_squared()
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if distance_sqr >= min_distance * min_distance:
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_add_point(new_position)
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maybe_exceeds_max_length = true
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# Reduce life and remove expired points.
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var remove_count := 0
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if max_lifetime != 0.:
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_decrease_life(delta)
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remove_count += _count_expired_points(remove_count)
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# Check if line length exceeds max length.
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if maybe_exceeds_max_length and max_length != 0.:
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remove_count += _count_overlength_points(remove_count)
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# Remove expired or overlength points.
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if remove_count > 0:
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_remove_oldest_points(remove_count)
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func _add_point(point_position: Vector2) -> void:
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add_point(point_position)
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var last_point_points_life := 0.
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for time in _points_life:
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last_point_points_life += time
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_points_life.append(max_lifetime - last_point_points_life)
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func _remove_oldest_points(remove_count: int) -> void:
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if remove_count > 0:
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points = points.slice(remove_count)
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_points_life = _points_life.slice(remove_count)
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func _decrease_life(delta: float, start_at := 0) -> void:
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var i := start_at
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while _points_life.size() > i and delta > 0.:
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var sub = minf(delta, _points_life[i])
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_points_life[i] -= sub
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delta -= sub
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i += 1
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func _count_expired_points(start_at := 0) -> int:
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var i := start_at
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while i < _points_life.size() and _points_life[i] <= 0.:
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i += 1
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return i - start_at
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func _count_overlength_points(start_at := 0) -> int:
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var length := 0.
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var all_points := points
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var previous_point := all_points[start_at]
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for i in range(start_at + 1, all_points.size()):
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var point := all_points[i]
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length += (point - previous_point).length()
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previous_point = point
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var overlength_count := 0
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while length > max_length and overlength_count < all_points.size() - 1:
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var removed_point = all_points[overlength_count]
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var next_point = all_points[overlength_count + 1]
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length -= (removed_point - next_point).length()
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overlength_count += 1
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return overlength_count
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