first commit

addons/zylann.hterrain/native/quad_tree_lod_generic.gd

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+@tool
+# Independent quad tree designed to handle LOD
+
+class HT_QTLQuad:
+	# Optional array of 4 HT_QTLQuad
+	var children = null
+	
+	# TODO Use Vector2i
+	var origin_x : int = 0
+	var origin_y : int = 0
+	
+	var data = null
+
+	func _init():
+		pass
+	
+	func clear():
+		clear_children()
+		data = null
+	
+	func clear_children():
+		children = null
+	
+	func has_children() -> bool:
+		return children != null
+
+
+var _tree := HT_QTLQuad.new()
+var _max_depth : int = 0
+var _base_size : int = 16
+var _split_scale : float = 2.0
+
+var _make_func : Callable
+var _recycle_func : Callable
+var _vertical_bounds_func : Callable
+
+
+func set_callbacks(make_cb: Callable, recycle_cb: Callable, vbounds_cb: Callable):
+	_make_func = make_cb
+	_recycle_func = recycle_cb
+	_vertical_bounds_func = vbounds_cb
+
+
+func clear():
+	_join_all_recursively(_tree, _max_depth)
+	_max_depth = 0
+	_base_size = 0
+
+
+static func compute_lod_count(base_size: int, full_size: int) -> int:
+	var po : int = 0
+	while full_size > base_size:
+		full_size = full_size >> 1
+		po += 1
+	return po
+
+
+func create_from_sizes(base_size: int, full_size: int):
+	clear()
+	_base_size = base_size
+	_max_depth = compute_lod_count(base_size, full_size)
+
+
+func get_lod_count() -> int:
+	# TODO _max_depth is a maximum, not a count. Would be better for it to be a count (+1)
+	return _max_depth + 1
+
+
+# The higher, the longer LODs will spread and higher the quality.
+# The lower, the shorter LODs will spread and lower the quality.
+func set_split_scale(p_split_scale: float):
+	var MIN := 2.0
+	var MAX := 5.0
+
+	# Split scale must be greater than a threshold,
+	# otherwise lods will decimate too fast and it will look messy
+	_split_scale = clampf(p_split_scale, MIN, MAX)
+
+
+func get_split_scale() -> float:
+	return _split_scale
+
+
+func update(view_pos: Vector3):
+	_update(_tree, _max_depth, view_pos)
+	
+	# This makes sure we keep seeing the lowest LOD,
+	# if the tree is cleared while we are far away
+	if not _tree.has_children() and _tree.data == null:
+		_tree.data = _make_chunk(_max_depth, 0, 0)
+
+
+func get_lod_factor(lod: int) -> int:
+	return 1 << lod
+
+
+func _update(quad: HT_QTLQuad, lod: int, view_pos: Vector3):
+	# This function should be called regularly over frames.
+	
+	var lod_factor : int = get_lod_factor(lod)
+	var chunk_size : int = _base_size * lod_factor
+	var world_center := \
+		chunk_size * (Vector3(quad.origin_x, 0, quad.origin_y) + Vector3(0.5, 0, 0.5))
+	
+	if _vertical_bounds_func.is_valid():
+		var vbounds : Vector2 = _vertical_bounds_func.call(quad.origin_x, quad.origin_y, lod)
+		world_center.y = (vbounds.x + vbounds.y) / 2.0
+	
+	var split_distance := _base_size * lod_factor * _split_scale
+	
+	if not quad.has_children():
+		if lod > 0 and world_center.distance_to(view_pos) < split_distance:
+			# Split
+			quad.children = [null, null, null, null]
+
+			for i in 4:
+				var child := HT_QTLQuad.new()
+				child.origin_x = quad.origin_x * 2 + (i & 1)
+				child.origin_y = quad.origin_y * 2 + ((i & 2) >> 1)
+				quad.children[i] = child
+				child.data = _make_chunk(lod - 1, child.origin_x, child.origin_y)
+				# If the quad needs to split more, we'll ask more recycling...
+
+			if quad.data != null:
+				_recycle_chunk(quad.data, quad.origin_x, quad.origin_y, lod)
+				quad.data = null
+	
+	else:
+		var no_split_child := true
+		
+		for child in quad.children:
+			_update(child, lod - 1, view_pos)
+			if child.has_children():
+				no_split_child = false
+		
+		if no_split_child and world_center.distance_to(view_pos) > split_distance:
+			# Join
+			for i in 4:
+				var child : HT_QTLQuad = quad.children[i]
+				_recycle_chunk(child.data, child.origin_x, child.origin_y, lod - 1)
+			quad.clear_children()
+			quad.data = _make_chunk(lod, quad.origin_x, quad.origin_y)
+
+
+func _join_all_recursively(quad: HT_QTLQuad, lod: int):
+	if quad.has_children():
+		for i in 4:
+			_join_all_recursively(quad.children[i], lod - 1)
+
+		quad.clear_children()
+
+	elif quad.data != null:
+		_recycle_chunk(quad.data, quad.origin_x, quad.origin_y, lod)
+		quad.data = null
+
+
+func _make_chunk(lod: int, origin_x: int, origin_y: int):
+	var chunk = null
+	if _make_func.is_valid():
+		chunk = _make_func.call(origin_x, origin_y, lod)
+	return chunk
+
+
+func _recycle_chunk(chunk, origin_x: int, origin_y: int, lod: int):
+	if _recycle_func.is_valid():
+		_recycle_func.call(chunk, origin_x, origin_y, lod)
+
+
+func debug_draw_tree(ci: CanvasItem):
+	var quad := _tree
+	_debug_draw_tree_recursive(ci, quad, _max_depth, 0)
+
+
+func _debug_draw_tree_recursive(ci: CanvasItem, quad: HT_QTLQuad, lod_index: int, child_index: int):
+	if quad.has_children():
+		for i in 4:
+			_debug_draw_tree_recursive(ci, quad.children[i], lod_index - 1, i)
+	else:
+		var size : int = get_lod_factor(lod_index)
+		var checker : int = 0
+		if child_index == 1 or child_index == 2:
+			checker = 1
+		var chunk_indicator : int = 0
+		if quad.data != null:
+			chunk_indicator = 1
+		var r := Rect2(Vector2(quad.origin_x, quad.origin_y) * size, Vector2(size, size))
+		ci.draw_rect(r, Color(1.0 - lod_index * 0.2, 0.2 * checker, chunk_indicator, 1))
+