first commit

addons/zylann.hterrain/native/.clang-format

@@ -0,0 +1,127 @@
+# Commented out parameters are those with the same value as base LLVM style
+# We can uncomment them if we want to change their value, or enforce the
+# chosen value in case the base style changes (last sync: Clang 6.0.1).
+---
+### General config, applies to all languages ###
+BasedOnStyle:  LLVM
+AccessModifierOffset: -4
+AlignAfterOpenBracket: DontAlign
+# AlignConsecutiveAssignments: false
+# AlignConsecutiveDeclarations: false
+# AlignEscapedNewlines: Right
+# AlignOperands:   true
+AlignTrailingComments: false
+AllowAllParametersOfDeclarationOnNextLine: false
+# AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortIfStatementsOnASingleLine: true
+# AllowShortLoopsOnASingleLine: false
+# AlwaysBreakAfterDefinitionReturnType: None
+# AlwaysBreakAfterReturnType: None
+# AlwaysBreakBeforeMultilineStrings: false
+# AlwaysBreakTemplateDeclarations: false
+# BinPackArguments: true
+# BinPackParameters: true
+# BraceWrapping:
+#   AfterClass:      false
+#   AfterControlStatement: false
+#   AfterEnum:       false
+#   AfterFunction:   false
+#   AfterNamespace:  false
+#   AfterObjCDeclaration: false
+#   AfterStruct:     false
+#   AfterUnion:      false
+#   AfterExternBlock: false
+#   BeforeCatch:     false
+#   BeforeElse:      false
+#   IndentBraces:    false
+#   SplitEmptyFunction: true
+#   SplitEmptyRecord: true
+#   SplitEmptyNamespace: true
+# BreakBeforeBinaryOperators: None
+# BreakBeforeBraces: Attach
+# BreakBeforeInheritanceComma: false
+BreakBeforeTernaryOperators: false
+# BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: AfterColon
+# BreakStringLiterals: true
+ColumnLimit:     0
+# CommentPragmas:  '^ IWYU pragma:'
+# CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 8
+ContinuationIndentWidth: 8
+Cpp11BracedListStyle: false
+# DerivePointerAlignment: false
+# DisableFormat:   false
+# ExperimentalAutoDetectBinPacking: false
+# FixNamespaceComments: true
+# ForEachMacros:
+#   - foreach
+#   - Q_FOREACH
+#   - BOOST_FOREACH
+# IncludeBlocks:   Preserve
+IncludeCategories:
+  - Regex:           '".*"'
+    Priority:        1
+  - Regex:           '^<.*\.h>'
+    Priority:        2
+  - Regex:           '^<.*'
+    Priority:        3
+# IncludeIsMainRegex: '(Test)?$'
+IndentCaseLabels: true
+# IndentPPDirectives: None
+IndentWidth:     4
+# IndentWrappedFunctionNames: false
+# JavaScriptQuotes: Leave
+# JavaScriptWrapImports: true
+# KeepEmptyLinesAtTheStartOfBlocks: true
+# MacroBlockBegin: ''
+# MacroBlockEnd:   ''
+# MaxEmptyLinesToKeep: 1
+# NamespaceIndentation: None
+# PenaltyBreakAssignment: 2
+# PenaltyBreakBeforeFirstCallParameter: 19
+# PenaltyBreakComment: 300
+# PenaltyBreakFirstLessLess: 120
+# PenaltyBreakString: 1000
+# PenaltyExcessCharacter: 1000000
+# PenaltyReturnTypeOnItsOwnLine: 60
+# PointerAlignment: Right
+# RawStringFormats:
+#   - Delimiter:       pb
+#     Language:        TextProto
+#     BasedOnStyle:    google
+# ReflowComments:  true
+# SortIncludes:    true
+# SortUsingDeclarations: true
+# SpaceAfterCStyleCast: false
+# SpaceAfterTemplateKeyword: true
+# SpaceBeforeAssignmentOperators: true
+# SpaceBeforeParens: ControlStatements
+# SpaceInEmptyParentheses: false
+# SpacesBeforeTrailingComments: 1
+# SpacesInAngles:  false
+# SpacesInContainerLiterals: true
+# SpacesInCStyleCastParentheses: false
+# SpacesInParentheses: false
+# SpacesInSquareBrackets: false
+TabWidth:        4
+UseTab:          Always
+---
+### C++ specific config ###
+Language:        Cpp
+Standard:        Cpp03
+---
+### ObjC specific config ###
+Language:        ObjC
+Standard:        Cpp03
+ObjCBlockIndentWidth: 4
+# ObjCSpaceAfterProperty: false
+# ObjCSpaceBeforeProtocolList: true
+---
+### Java specific config ###
+Language:        Java
+# BreakAfterJavaFieldAnnotations: false
+...

addons/zylann.hterrain/native/.gitignore

@@ -0,0 +1,4 @@
+# Build
+# Ignored locally because there are other folders in which we want to version OBJ files
+*.obj
+

addons/zylann.hterrain/native/SConstruct

@@ -0,0 +1,119 @@
+#!python
+import os
+
+opts = Variables([], ARGUMENTS)
+
+# Gets the standard flags CC, CCX, etc.
+env = Environment(ENV = os.environ)
+
+# Define our options
+opts.Add(EnumVariable('target', "Compilation target", 'debug', ['debug', 'release']))
+opts.Add(EnumVariable('platform', "Compilation platform", '', ['', 'windows', 'linux', 'osx']))
+opts.Add(BoolVariable('use_llvm', "Use the LLVM / Clang compiler", 'no'))
+opts.Add(EnumVariable('macos_arch', "Target macOS architecture", 'universal', ['universal', 'x86_64', 'arm64']))
+
+# Hardcoded ones
+target_path = "bin/"
+TARGET_NAME = "hterrain_native"
+
+# Local dependency paths
+godot_headers_path = "godot-cpp/godot-headers/"
+cpp_bindings_path = "godot-cpp/"
+cpp_bindings_library = "libgodot-cpp"
+
+# only support 64 at this time
+bits = 64
+
+# Updates the environment with the option variables.
+opts.Update(env)
+
+# Process some arguments
+if env['use_llvm']:
+    env['CC'] = 'clang'
+    env['CXX'] = 'clang++'
+
+if env['platform'] == '':
+    print("No valid target platform selected.")
+    quit()
+
+# For the reference:
+# - CCFLAGS are compilation flags shared between C and C++
+# - CFLAGS are for C-specific compilation flags
+# - CXXFLAGS are for C++-specific compilation flags
+# - CPPFLAGS are for pre-processor flags
+# - CPPDEFINES are for pre-processor defines
+# - LINKFLAGS are for linking flags
+
+# Check our platform specifics
+if env['platform'] == "osx":
+    target_path += 'osx/'
+    cpp_bindings_library += '.osx'
+    if env['target'] == 'debug':
+        env.Append(CCFLAGS = ['-g', '-O2', '-arch', 'x86_64'])
+        env.Append(CXXFLAGS = ['-std=c++17'])
+        env.Append(LINKFLAGS = ['-arch', 'x86_64'])
+    else:
+        env.Append(CCFLAGS = ['-g', '-O3', '-arch', 'x86_64'])
+        env.Append(CXXFLAGS = ['-std=c++17'])
+        env.Append(LINKFLAGS = ['-arch', 'x86_64'])
+
+elif env['platform'] == "linux":
+    target_path += 'linux/'
+    cpp_bindings_library += '.linux'
+    if env['target'] == 'debug':
+        # -g3 means we want plenty of debug info, more than default
+        env.Append(CCFLAGS = ['-fPIC', '-g3', '-Og'])
+        env.Append(CXXFLAGS = ['-std=c++17'])
+    else:
+        env.Append(CCFLAGS = ['-fPIC', '-O3'])
+        env.Append(CXXFLAGS = ['-std=c++17'])
+        env.Append(LINKFLAGS = ['-s'])
+
+elif env['platform'] == "windows":
+    target_path += 'win64/'
+    cpp_bindings_library += '.windows'
+    # This makes sure to keep the session environment variables on windows,
+    # that way you can run scons in a vs 2017 prompt and it will find all the required tools
+    #env.Append(ENV = os.environ)
+
+    env.Append(CPPDEFINES = ['WIN32', '_WIN32', '_WINDOWS', '_CRT_SECURE_NO_WARNINGS'])
+    env.Append(CCFLAGS = ['-W3', '-GR'])
+    if env['target'] == 'debug':
+        env.Append(CPPDEFINES = ['_DEBUG'])
+        env.Append(CCFLAGS = ['-EHsc', '-MDd', '-ZI'])
+        env.Append(LINKFLAGS = ['-DEBUG'])
+    else:
+        env.Append(CPPDEFINES = ['NDEBUG'])
+        env.Append(CCFLAGS = ['-O2', '-EHsc', '-MD'])
+
+if env['target'] == 'debug':
+    cpp_bindings_library += '.debug'
+else:
+    cpp_bindings_library += '.release'
+
+if env['macos_arch'] == 'universal':
+    cpp_bindings_library += '.' + str(bits)
+else:
+    cpp_bindings_library += '.' + env['macos_arch']
+
+# make sure our binding library is properly included
+env.Append(CPPPATH = [
+    '.', 
+    godot_headers_path, 
+    cpp_bindings_path + 'include/',
+    cpp_bindings_path + 'include/core/',
+    cpp_bindings_path + 'include/gen/'
+])
+env.Append(LIBPATH = [cpp_bindings_path + 'bin/'])
+env.Append(LIBS = [cpp_bindings_library])
+
+# Add source files of our library
+env.Append(CPPPATH = ['src/'])
+sources = Glob('src/*.cpp')
+
+library = env.SharedLibrary(target = target_path + TARGET_NAME , source = sources)
+
+Default(library)
+
+# Generates help for the -h scons option.
+Help(opts.GenerateHelpText(env))

addons/zylann.hterrain/native/factory.gd

@@ -0,0 +1,55 @@
+@tool
+
+const NATIVE_PATH = "res://addons/zylann.hterrain/native/"
+
+const HT_ImageUtilsGeneric = preload("./image_utils_generic.gd")
+const HT_QuadTreeLodGeneric = preload("./quad_tree_lod_generic.gd")
+
+# No native code was ported when moving to Godot 4.
+# It may be changed too using GDExtension.
+
+# See https://docs.godotengine.org/en/stable/classes/class_os.html#class-os-method-get-name
+const _supported_os = {
+	# "Windows": true,
+	# "X11": true,
+	# "OSX": true
+}
+# See https://docs.godotengine.org/en/stable/tutorials/export/feature_tags.html
+const _supported_archs = ["x86_64"]
+
+
+static func _supports_current_arch() -> bool:
+	for arch in _supported_archs:
+		# This is misleading, we are querying features of the ENGINE, not the OS
+		if OS.has_feature(arch):
+			return true
+	return false
+
+
+static func is_native_available() -> bool:
+	if not _supports_current_arch():
+		return false
+	var os = OS.get_name()
+	if not _supported_os.has(os):
+		return false
+	# API changes can cause binary incompatibility
+	var v = Engine.get_version_info()
+	return v.major == 4 and v.minor == 0
+
+
+static func get_image_utils():
+	if is_native_available():
+		var HT_ImageUtilsNative = load(NATIVE_PATH + "image_utils.gdns")
+		# TODO Godot doesn't always return `null` when it fails so that `if` doesn't always help...
+		# See https://github.com/Zylann/godot_heightmap_plugin/issues/331
+		if HT_ImageUtilsNative != null:
+			return HT_ImageUtilsNative.new()
+	return HT_ImageUtilsGeneric.new()
+
+
+static func get_quad_tree_lod():
+	if is_native_available():
+		var HT_QuadTreeLod = load(NATIVE_PATH + "quad_tree_lod.gdns")
+		if HT_QuadTreeLod != null:
+			return HT_QuadTreeLod.new()
+	return HT_QuadTreeLodGeneric.new()

addons/zylann.hterrain/native/factory.gd.uid

@@ -0,0 +1 @@
+uid://cupyw3v6cqa4n

addons/zylann.hterrain/native/image_utils_generic.gd

@@ -0,0 +1,316 @@
+@tool
+
+# These functions are the same as the ones found in the GDNative library.
+# They are used if the user's platform is not supported.
+
+const HT_Util = preload("../util/util.gd")
+
+var _blur_buffer : Image
+
+
+func get_red_range(im: Image, rect: Rect2) -> Vector2:
+	rect = rect.intersection(Rect2(0, 0, im.get_width(), im.get_height()))
+	var min_x := int(rect.position.x)
+	var min_y := int(rect.position.y)
+	var max_x := min_x + int(rect.size.x)
+	var max_y := min_y + int(rect.size.y)
+
+	var min_height := im.get_pixel(min_x, min_y).r
+	var max_height := min_height
+
+	for y in range(min_y, max_y):
+		for x in range(min_x, max_x):
+			var h = im.get_pixel(x, y).r
+			if h < min_height:
+				min_height = h
+			elif h > max_height:
+				max_height = h
+
+	return Vector2(min_height, max_height)
+
+
+func get_red_sum(im: Image, rect: Rect2) -> float:
+	rect = rect.intersection(Rect2(0, 0, im.get_width(), im.get_height()))
+	var min_x := int(rect.position.x)
+	var min_y := int(rect.position.y)
+	var max_x := min_x + int(rect.size.x)
+	var max_y := min_y + int(rect.size.y)
+
+	var sum := 0.0
+	
+	for y in range(min_y, max_y):
+		for x in range(min_x, max_x):
+			sum += im.get_pixel(x, y).r
+
+	return sum
+
+
+func get_red_sum_weighted(im: Image, brush: Image, pos: Vector2, factor: float) -> float:
+	var min_x = int(pos.x)
+	var min_y = int(pos.y)
+	var max_x = min_x + brush.get_width()
+	var max_y = min_y + brush.get_height()
+	var min_noclamp_x = min_x
+	var min_noclamp_y = min_y
+
+	min_x = clampi(min_x, 0, im.get_width())
+	min_y = clampi(min_y, 0, im.get_height())
+	max_x = clampi(max_x, 0, im.get_width())
+	max_y = clampi(max_y, 0, im.get_height())
+
+	var sum = 0.0
+
+	for y in range(min_y, max_y):
+		var by = y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx = x - min_noclamp_x
+			
+			var shape_value = brush.get_pixel(bx, by).r
+			sum += im.get_pixel(x, y).r * shape_value * factor
+
+	return sum
+
+
+func add_red_brush(im: Image, brush: Image, pos: Vector2, factor: float):
+	var min_x = int(pos.x)
+	var min_y = int(pos.y)
+	var max_x = min_x + brush.get_width()
+	var max_y = min_y + brush.get_height()
+	var min_noclamp_x = min_x
+	var min_noclamp_y = min_y
+
+	min_x = clampi(min_x, 0, im.get_width())
+	min_y = clampi(min_y, 0, im.get_height())
+	max_x = clampi(max_x, 0, im.get_width())
+	max_y = clampi(max_y, 0, im.get_height())
+
+	for y in range(min_y, max_y):
+		var by = y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx = x - min_noclamp_x
+
+			var shape_value = brush.get_pixel(bx, by).r
+			var r = im.get_pixel(x, y).r + shape_value * factor
+			im.set_pixel(x, y, Color(r, r, r))
+
+
+func lerp_channel_brush(im: Image, brush: Image, pos: Vector2, 
+	factor: float, target_value: float, channel: int):
+		
+	var min_x = int(pos.x)
+	var min_y = int(pos.y)
+	var max_x = min_x + brush.get_width()
+	var max_y = min_y + brush.get_height()
+	var min_noclamp_x = min_x
+	var min_noclamp_y = min_y
+
+	min_x = clampi(min_x, 0, im.get_width())
+	min_y = clampi(min_y, 0, im.get_height())
+	max_x = clampi(max_x, 0, im.get_width())
+	max_y = clampi(max_y, 0, im.get_height())
+
+	for y in range(min_y, max_y):
+		var by = y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx = x - min_noclamp_x
+
+			var shape_value = brush.get_pixel(bx, by).r
+			var c = im.get_pixel(x, y)
+			c[channel] = lerp(c[channel], target_value, shape_value * factor)
+			im.set_pixel(x, y, c)
+
+
+func lerp_color_brush(im: Image, brush: Image, pos: Vector2, 
+	factor: float, target_value: Color):
+		
+	var min_x = int(pos.x)
+	var min_y = int(pos.y)
+	var max_x = min_x + brush.get_width()
+	var max_y = min_y + brush.get_height()
+	var min_noclamp_x = min_x
+	var min_noclamp_y = min_y
+
+	min_x = clampi(min_x, 0, im.get_width())
+	min_y = clampi(min_y, 0, im.get_height())
+	max_x = clampi(max_x, 0, im.get_width())
+	max_y = clampi(max_y, 0, im.get_height())
+
+	for y in range(min_y, max_y):
+		var by = y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx = x - min_noclamp_x
+
+			var shape_value = brush.get_pixel(bx, by).r
+			var c = im.get_pixel(x, y).lerp(target_value, factor * shape_value)
+			im.set_pixel(x, y, c)
+
+
+func generate_gaussian_brush(im: Image) -> float:
+	var sum := 0.0
+	var center := Vector2(im.get_width() / 2, im.get_height() / 2)
+	var radius := minf(im.get_width(), im.get_height()) / 2.0
+
+	for y in im.get_height():
+		for x in im.get_width():
+			var d := Vector2(x, y).distance_to(center) / radius
+			var v := clampf(1.0 - d * d * d, 0.0, 1.0)
+			im.set_pixel(x, y, Color(v, v, v))
+			sum += v;
+
+	return sum
+
+
+func blur_red_brush(im: Image, brush: Image, pos: Vector2, factor: float):
+	factor = clampf(factor, 0.0, 1.0)
+	
+	if _blur_buffer == null:
+		_blur_buffer = Image.new()
+	var buffer := _blur_buffer
+	
+	var buffer_width := brush.get_width() + 2
+	var buffer_height := brush.get_height() + 2
+	
+	if buffer_width != buffer.get_width() or buffer_height != buffer.get_height():
+		buffer.create(buffer_width, buffer_height, false, Image.FORMAT_RF)
+	
+	var min_x := int(pos.x) - 1
+	var min_y := int(pos.y) - 1
+	var max_x := min_x + buffer.get_width()
+	var max_y := min_y + buffer.get_height()
+	
+	var im_clamp_w = im.get_width() - 1
+	var im_clamp_h = im.get_height() - 1
+	
+	# Copy pixels to temporary buffer
+	for y in range(min_y, max_y):
+		for x in range(min_x, max_x):
+			var ix := clampi(x, 0, im_clamp_w)
+			var iy := clampi(y, 0, im_clamp_h)
+			var c = im.get_pixel(ix, iy)
+			buffer.set_pixel(x - min_x, y - min_y, c)
+	
+	min_x = int(pos.x)
+	min_y = int(pos.y)
+	max_x = min_x + brush.get_width()
+	max_y = min_y + brush.get_height()
+	var min_noclamp_x := min_x
+	var min_noclamp_y := min_y
+
+	min_x = clampi(min_x, 0, im.get_width())
+	min_y = clampi(min_y, 0, im.get_height())
+	max_x = clampi(max_x, 0, im.get_width())
+	max_y = clampi(max_y, 0, im.get_height())
+	
+	# Apply blur
+	for y in range(min_y, max_y):
+		var by := y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx := x - min_noclamp_x
+
+			var shape_value := brush.get_pixel(bx, by).r * factor
+
+			var p10 = buffer.get_pixel(bx + 1, by    ).r
+			var p01 = buffer.get_pixel(bx,     by + 1).r
+			var p11 = buffer.get_pixel(bx + 1, by + 1).r
+			var p21 = buffer.get_pixel(bx + 2, by + 1).r
+			var p12 = buffer.get_pixel(bx + 1, by + 2).r
+			
+			var m = (p10 + p01 + p11 + p21 + p12) * 0.2
+			var p = lerpf(p11, m, shape_value * factor)
+
+			im.set_pixel(x, y, Color(p, p, p))
+
+
+func paint_indexed_splat(index_map: Image, weight_map: Image, brush: Image, pos: Vector2, \
+	texture_index: int, factor: float):
+	
+	var min_x := pos.x
+	var min_y := pos.y
+	var max_x := min_x + brush.get_width()
+	var max_y := min_y + brush.get_height()
+	var min_noclamp_x := min_x
+	var min_noclamp_y := min_y
+
+	min_x = clampi(min_x, 0, index_map.get_width())
+	min_y = clampi(min_y, 0, index_map.get_height())
+	max_x = clampi(max_x, 0, index_map.get_width())
+	max_y = clampi(max_y, 0, index_map.get_height())
+	
+	var texture_index_f := float(texture_index) / 255.0
+	var all_texture_index_f := Color(texture_index_f, texture_index_f, texture_index_f)
+	var ci := texture_index % 3
+	var cm := Color(-1, -1, -1)
+	cm[ci] = 1
+
+	for y in range(min_y, max_y):
+		var by := y - min_noclamp_y
+
+		for x in range(min_x, max_x):
+			var bx := x - min_noclamp_x
+
+			var shape_value := brush.get_pixel(bx, by).r * factor
+			if shape_value == 0.0:
+				continue
+
+			var i := index_map.get_pixel(x, y)
+			var w := weight_map.get_pixel(x, y)
+			
+			# Decompress third weight to make computations easier
+			w[2] = 1.0 - w[0] - w[1]
+			
+			# The index map tells which textures to blend.
+			# The weight map tells their blending amounts.
+			# This brings the limitation that up to 3 textures can blend at a time in a given pixel.
+			# Painting this in real time can be a challenge.
+			
+			# The approach here is a compromise for simplicity.
+			# Each texture is associated a fixed component of the index map (R, G or B),
+			# so two neighbor pixels having the same component won't be guaranteed to blend.
+			# In other words, texture T will not be able to blend with T + N * k,
+			# where k is an integer, and N is the number of components in the index map (up to 4).
+			# It might still be able to blend due to a special case when an area is uniform,
+			# but not otherwise.
+			
+			# Dynamic component assignment sounds like the alternative, however I wasn't able
+			# to find a painting algorithm that wasn't confusing, at least the current one is
+			# predictable.
+			
+			# Need to use approximation because Color is float but GDScript uses doubles...
+			if abs(i[ci] - texture_index_f) > 0.001:
+				# Pixel does not have our texture index,
+				# transfer its weight to other components first
+				if w[ci] > shape_value:
+					w -= cm * shape_value
+					
+				elif w[ci] >= 0.0:
+					w[ci] = 0.0
+					i[ci] = texture_index_f
+					
+			else:
+				# Pixel has our texture index, increase its weight
+				if w[ci] + shape_value < 1.0:
+					w += cm * shape_value
+					
+				else:
+					# Pixel weight is full, we can set all components to the same index.
+					# Need to nullify other weights because they would otherwise never reach
+					# zero due to normalization
+					w = Color(0, 0, 0)
+					w[ci] = 1.0
+					i = all_texture_index_f
+			
+			# No `saturate` function in Color??
+			w[0] = clampf(w[0], 0.0, 1.0)
+			w[1] = clampf(w[1], 0.0, 1.0)
+			w[2] = clampf(w[2], 0.0, 1.0)
+			
+			# Renormalize
+			w /= w[0] + w[1] + w[2]
+			
+			index_map.set_pixel(x, y, i)
+			weight_map.set_pixel(x, y, w)

addons/zylann.hterrain/native/image_utils_generic.gd.uid

@@ -0,0 +1 @@
+uid://2f87sp1jmfe1

addons/zylann.hterrain/native/quad_tree_lod_generic.gd

@@ -0,0 +1,188 @@
+@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))
+

addons/zylann.hterrain/native/quad_tree_lod_generic.gd.uid

@@ -0,0 +1 @@
+uid://ci5njrvvrqucr

addons/zylann.hterrain/native/src/gd_library.cpp

@@ -0,0 +1,30 @@
+#include "image_utils.h"
+#include "quad_tree_lod.h"
+
+extern "C" {
+
+void GDN_EXPORT godot_gdnative_init(godot_gdnative_init_options *o) {
+#ifdef _DEBUG
+    printf("godot_gdnative_init hterrain_native\n");
+#endif
+    godot::Godot::gdnative_init(o);
+}
+
+void GDN_EXPORT godot_gdnative_terminate(godot_gdnative_terminate_options *o) {
+#ifdef _DEBUG
+    printf("godot_gdnative_terminate hterrain_native\n");
+#endif
+    godot::Godot::gdnative_terminate(o);
+}
+
+void GDN_EXPORT godot_nativescript_init(void *handle) {
+#ifdef _DEBUG
+    printf("godot_nativescript_init hterrain_native\n");
+#endif
+    godot::Godot::nativescript_init(handle);
+
+    godot::register_tool_class<godot::ImageUtils>();
+    godot::register_tool_class<godot::QuadTreeLod>();
+}
+
+} // extern "C"

addons/zylann.hterrain/native/src/image_utils.cpp

@@ -0,0 +1,364 @@
+#include "image_utils.h"
+#include "int_range_2d.h"
+#include "math_funcs.h"
+
+namespace godot {
+
+template <typename F>
+inline void generic_brush_op(Image &image, Image &brush, Vector2 p_pos, float factor, F op) {
+	IntRange2D range = IntRange2D::from_min_max(p_pos, brush.get_size());
+	int min_x_noclamp = range.min_x;
+	int min_y_noclamp = range.min_y;
+	range.clip(Vector2i(image.get_size()));
+
+	image.lock();
+	brush.lock();
+
+	for (int y = range.min_y; y < range.max_y; ++y) {
+		int by = y - min_y_noclamp;
+
+		for (int x = range.min_x; x < range.max_x; ++x) {
+			int bx = x - min_x_noclamp;
+
+			float b = brush.get_pixel(bx, by).r * factor;
+			op(image, x, y, b);
+		}
+	}
+
+	image.unlock();
+	brush.unlock();
+}
+
+ImageUtils::ImageUtils() {
+#ifdef _DEBUG
+	Godot::print("Constructing ImageUtils");
+#endif
+}
+
+ImageUtils::~ImageUtils() {
+#ifdef _DEBUG
+	// TODO Cannot print shit here, see https://github.com/godotengine/godot/issues/37417
+	// Means only the console will print this
+	//Godot::print("Destructing ImageUtils");
+	printf("Destructing ImageUtils\n");
+#endif
+}
+
+void ImageUtils::_init() {
+}
+
+Vector2 ImageUtils::get_red_range(Ref<Image> image_ref, Rect2 rect) const {
+	ERR_FAIL_COND_V(image_ref.is_null(), Vector2());
+	Image &image = **image_ref;
+
+	IntRange2D range(rect);
+	range.clip(Vector2i(image.get_size()));
+
+	image.lock();
+
+	float min_value = image.get_pixel(range.min_x, range.min_y).r;
+	float max_value = min_value;
+
+	for (int y = range.min_y; y < range.max_y; ++y) {
+		for (int x = range.min_x; x < range.max_x; ++x) {
+			float v = image.get_pixel(x, y).r;
+
+			if (v > max_value) {
+				max_value = v;
+			} else if (v < min_value) {
+				min_value = v;
+			}
+		}
+	}
+
+	image.unlock();
+
+	return Vector2(min_value, max_value);
+}
+
+float ImageUtils::get_red_sum(Ref<Image> image_ref, Rect2 rect) const {
+	ERR_FAIL_COND_V(image_ref.is_null(), 0.f);
+	Image &image = **image_ref;
+
+	IntRange2D range(rect);
+	range.clip(Vector2i(image.get_size()));
+
+	image.lock();
+
+	float sum = 0.f;
+
+	for (int y = range.min_y; y < range.max_y; ++y) {
+		for (int x = range.min_x; x < range.max_x; ++x) {
+			sum += image.get_pixel(x, y).r;
+		}
+	}
+
+	image.unlock();
+
+	return sum;
+}
+
+float ImageUtils::get_red_sum_weighted(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor) const {
+	ERR_FAIL_COND_V(image_ref.is_null(), 0.f);
+	ERR_FAIL_COND_V(brush_ref.is_null(), 0.f);
+	Image &image = **image_ref;
+	Image &brush = **brush_ref;
+
+	float sum = 0.f;
+	generic_brush_op(image, brush, p_pos, factor, [&sum](Image &image, int x, int y, float b) {
+		sum += image.get_pixel(x, y).r * b;
+	});
+
+	return sum;
+}
+
+void ImageUtils::add_red_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor) const {
+	ERR_FAIL_COND(image_ref.is_null());
+	ERR_FAIL_COND(brush_ref.is_null());
+	Image &image = **image_ref;
+	Image &brush = **brush_ref;
+
+	generic_brush_op(image, brush, p_pos, factor, [](Image &image, int x, int y, float b) {
+		float r = image.get_pixel(x, y).r + b;
+		image.set_pixel(x, y, Color(r, r, r));
+	});
+}
+
+void ImageUtils::lerp_channel_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor, float target_value, int channel) const {
+	ERR_FAIL_COND(image_ref.is_null());
+	ERR_FAIL_COND(brush_ref.is_null());
+	Image &image = **image_ref;
+	Image &brush = **brush_ref;
+
+	generic_brush_op(image, brush, p_pos, factor, [target_value, channel](Image &image, int x, int y, float b) {
+		Color c = image.get_pixel(x, y);
+		c[channel] = Math::lerp(c[channel], target_value, b);
+		image.set_pixel(x, y, c);
+	});
+}
+
+void ImageUtils::lerp_color_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor, Color target_value) const {
+	ERR_FAIL_COND(image_ref.is_null());
+	ERR_FAIL_COND(brush_ref.is_null());
+	Image &image = **image_ref;
+	Image &brush = **brush_ref;
+
+	generic_brush_op(image, brush, p_pos, factor, [target_value](Image &image, int x, int y, float b) {
+		const Color c = image.get_pixel(x, y).linear_interpolate(target_value, b);
+		image.set_pixel(x, y, c);
+	});
+}
+
+// TODO Smooth (each pixel being box-filtered, contrary to the existing smooth)
+
+float ImageUtils::generate_gaussian_brush(Ref<Image> image_ref) const {
+	ERR_FAIL_COND_V(image_ref.is_null(), 0.f);
+	Image &image = **image_ref;
+
+	int w = static_cast<int>(image.get_width());
+	int h = static_cast<int>(image.get_height());
+	Vector2 center(w / 2, h / 2);
+	float radius = Math::min(w, h) / 2;
+
+	ERR_FAIL_COND_V(radius <= 0.1f, 0.f);
+
+	float sum = 0.f;
+	image.lock();
+
+	for (int y = 0; y < h; ++y) {
+		for (int x = 0; x < w; ++x) {
+			float d = Vector2(x, y).distance_to(center) / radius;
+			float v = Math::clamp(1.f - d * d * d, 0.f, 1.f);
+			image.set_pixel(x, y, Color(v, v, v));
+			sum += v;
+		}
+	}
+
+	image.unlock();
+	return sum;
+}
+
+void ImageUtils::blur_red_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor) {
+	ERR_FAIL_COND(image_ref.is_null());
+	ERR_FAIL_COND(brush_ref.is_null());
+	Image &image = **image_ref;
+	Image &brush = **brush_ref;
+
+	factor = Math::clamp(factor, 0.f, 1.f);
+
+	// Relative to the image
+	IntRange2D buffer_range = IntRange2D::from_pos_size(p_pos, brush.get_size());
+	buffer_range.pad(1);
+
+	const int image_width = static_cast<int>(image.get_width());
+	const int image_height = static_cast<int>(image.get_height());
+
+	const int buffer_width = static_cast<int>(buffer_range.get_width());
+	const int buffer_height = static_cast<int>(buffer_range.get_height());
+	_blur_buffer.resize(buffer_width * buffer_height);
+
+	image.lock();
+
+	// Cache pixels, because they will be queried more than once and written to later
+	int buffer_i = 0;
+	for (int y = buffer_range.min_y; y < buffer_range.max_y; ++y) {
+		for (int x = buffer_range.min_x; x < buffer_range.max_x; ++x) {
+			const int ix = Math::clamp(x, 0, image_width - 1);
+			const int iy = Math::clamp(y, 0, image_height - 1);
+			_blur_buffer[buffer_i] = image.get_pixel(ix, iy).r;
+			++buffer_i;
+		}
+	}
+
+	IntRange2D range = IntRange2D::from_min_max(p_pos, brush.get_size());
+	const int min_x_noclamp = range.min_x;
+	const int min_y_noclamp = range.min_y;
+	range.clip(Vector2i(image.get_size()));
+
+	const int buffer_offset_left = -1;
+	const int buffer_offset_right = 1;
+	const int buffer_offset_top = -buffer_width;
+	const int buffer_offset_bottom = buffer_width;
+
+	brush.lock();
+
+	// Apply blur
+	for (int y = range.min_y; y < range.max_y; ++y) {
+		const int brush_y = y - min_y_noclamp;
+
+		for (int x = range.min_x; x < range.max_x; ++x) {
+			const int brush_x = x - min_x_noclamp;
+
+			const float brush_value = brush.get_pixel(brush_x, brush_y).r * factor;
+
+			buffer_i = (brush_x + 1) + (brush_y + 1) * buffer_width;
+
+			const float p10 = _blur_buffer[buffer_i + buffer_offset_top];
+			const float p01 = _blur_buffer[buffer_i + buffer_offset_left];
+			const float p11 = _blur_buffer[buffer_i];
+			const float p21 = _blur_buffer[buffer_i + buffer_offset_right];
+			const float p12 = _blur_buffer[buffer_i + buffer_offset_bottom];
+
+			// Average
+			float m = (p10 + p01 + p11 + p21 + p12) * 0.2f;
+			float p = Math::lerp(p11, m, brush_value);
+
+			image.set_pixel(x, y, Color(p, p, p));
+		}
+	}
+
+	image.unlock();
+	brush.unlock();
+}
+
+void ImageUtils::paint_indexed_splat(Ref<Image> index_map_ref, Ref<Image> weight_map_ref,
+		Ref<Image> brush_ref, Vector2 p_pos, int texture_index, float factor) {
+
+	ERR_FAIL_COND(index_map_ref.is_null());
+	ERR_FAIL_COND(weight_map_ref.is_null());
+	ERR_FAIL_COND(brush_ref.is_null());
+	Image &index_map = **index_map_ref;
+	Image &weight_map = **weight_map_ref;
+	Image &brush = **brush_ref;
+
+	ERR_FAIL_COND(index_map.get_size() != weight_map.get_size());
+
+	factor = Math::clamp(factor, 0.f, 1.f);
+
+	IntRange2D range = IntRange2D::from_min_max(p_pos, brush.get_size());
+	const int min_x_noclamp = range.min_x;
+	const int min_y_noclamp = range.min_y;
+	range.clip(Vector2i(index_map.get_size()));
+
+	const float texture_index_f = float(texture_index) / 255.f;
+	const Color all_texture_index_f(texture_index_f, texture_index_f, texture_index_f);
+	const int ci = texture_index % 3;
+	Color cm(-1, -1, -1);
+	cm[ci] = 1;
+
+	brush.lock();
+	index_map.lock();
+	weight_map.lock();
+
+	for (int y = range.min_y; y < range.max_y; ++y) {
+		const int brush_y = y - min_y_noclamp;
+
+		for (int x = range.min_x; x < range.max_x; ++x) {
+			const int brush_x = x - min_x_noclamp;
+
+			const float brush_value = brush.get_pixel(brush_x, brush_y).r * factor;
+
+			if (brush_value == 0.f) {
+				continue;
+			}
+
+			Color i = index_map.get_pixel(x, y);
+			Color w = weight_map.get_pixel(x, y);
+
+			// Decompress third weight to make computations easier
+			w[2] = 1.f - w[0] - w[1];
+
+			if (std::abs(i[ci] - texture_index_f) > 0.001f) {
+				// Pixel does not have our texture index,
+				// transfer its weight to other components first
+				if (w[ci] > brush_value) {
+					w[0] -= cm[0] * brush_value;
+					w[1] -= cm[1] * brush_value;
+					w[2] -= cm[2] * brush_value;
+
+				} else if (w[ci] >= 0.f) {
+					w[ci] = 0.f;
+					i[ci] = texture_index_f;
+				}
+
+			} else {
+				// Pixel has our texture index, increase its weight
+				if (w[ci] + brush_value < 1.f) {
+					w[0] += cm[0] * brush_value;
+					w[1] += cm[1] * brush_value;
+					w[2] += cm[2] * brush_value;
+
+				} else {
+					// Pixel weight is full, we can set all components to the same index.
+					// Need to nullify other weights because they would otherwise never reach
+					// zero due to normalization
+					w = Color(0, 0, 0);
+					w[ci] = 1.0;
+					i = all_texture_index_f;
+				}
+			}
+
+			// No `saturate` function in Color??
+			w[0] = Math::clamp(w[0], 0.f, 1.f);
+			w[1] = Math::clamp(w[1], 0.f, 1.f);
+			w[2] = Math::clamp(w[2], 0.f, 1.f);
+
+			// Renormalize
+			const float sum = w[0] + w[1] + w[2];
+			w[0] /= sum;
+			w[1] /= sum;
+			w[2] /= sum;
+
+			index_map.set_pixel(x, y, i);
+			weight_map.set_pixel(x, y, w);
+		}
+	}
+
+	brush.lock();
+	index_map.unlock();
+	weight_map.unlock();
+}
+
+void ImageUtils::_register_methods() {
+	register_method("get_red_range", &ImageUtils::get_red_range);
+	register_method("get_red_sum", &ImageUtils::get_red_sum);
+	register_method("get_red_sum_weighted", &ImageUtils::get_red_sum_weighted);
+	register_method("add_red_brush", &ImageUtils::add_red_brush);
+	register_method("lerp_channel_brush", &ImageUtils::lerp_channel_brush);
+	register_method("lerp_color_brush", &ImageUtils::lerp_color_brush);
+	register_method("generate_gaussian_brush", &ImageUtils::generate_gaussian_brush);
+	register_method("blur_red_brush", &ImageUtils::blur_red_brush);
+	register_method("paint_indexed_splat", &ImageUtils::paint_indexed_splat);
+}
+
+} // namespace godot

addons/zylann.hterrain/native/src/image_utils.h

@@ -0,0 +1,38 @@
+#ifndef IMAGE_UTILS_H
+#define IMAGE_UTILS_H
+
+#include <core/Godot.hpp>
+#include <gen/Image.hpp>
+#include <gen/Reference.hpp>
+#include <vector>
+
+namespace godot {
+
+class ImageUtils : public Reference {
+    GODOT_CLASS(ImageUtils, Reference)
+public:
+    static void _register_methods();
+
+    ImageUtils();
+    ~ImageUtils();
+
+    void _init();
+
+    Vector2 get_red_range(Ref<Image> image_ref, Rect2 rect) const;
+    float get_red_sum(Ref<Image> image_ref, Rect2 rect) const;
+    float get_red_sum_weighted(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor) const;
+    void add_red_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor) const;
+    void lerp_channel_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor, float target_value, int channel) const;
+    void lerp_color_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor, Color target_value) const;
+    float generate_gaussian_brush(Ref<Image> image_ref) const;
+    void blur_red_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor);
+    void paint_indexed_splat(Ref<Image> index_map_ref, Ref<Image> weight_map_ref, Ref<Image> brush_ref, Vector2 p_pos, int texture_index, float factor);
+    //void erode_red_brush(Ref<Image> image_ref, Ref<Image> brush_ref, Vector2 p_pos, float factor);
+
+private:
+    std::vector<float> _blur_buffer;
+};
+
+} // namespace godot
+
+#endif // IMAGE_UTILS_H

addons/zylann.hterrain/native/src/int_range_2d.h

@@ -0,0 +1,59 @@
+#ifndef INT_RANGE_2D_H
+#define INT_RANGE_2D_H
+
+#include "math_funcs.h"
+#include "vector2i.h"
+#include <core/Rect2.hpp>
+
+struct IntRange2D {
+    int min_x;
+    int min_y;
+    int max_x;
+    int max_y;
+
+    static inline IntRange2D from_min_max(godot::Vector2 min_pos, godot::Vector2 max_pos) {
+        return IntRange2D(godot::Rect2(min_pos, max_pos));
+    }
+
+    static inline IntRange2D from_pos_size(godot::Vector2 min_pos, godot::Vector2 size) {
+        return IntRange2D(godot::Rect2(min_pos, size));
+    }
+
+    IntRange2D(godot::Rect2 rect) {
+        min_x = static_cast<int>(rect.position.x);
+        min_y = static_cast<int>(rect.position.y);
+        max_x = static_cast<int>(rect.position.x + rect.size.x);
+        max_y = static_cast<int>(rect.position.y + rect.size.y);
+    }
+
+    inline bool is_inside(Vector2i size) const {
+        return min_x >= size.x &&
+               min_y >= size.y &&
+               max_x <= size.x &&
+               max_y <= size.y;
+    }
+
+    inline void clip(Vector2i size) {
+        min_x = Math::clamp(min_x, 0, size.x);
+        min_y = Math::clamp(min_y, 0, size.y);
+        max_x = Math::clamp(max_x, 0, size.x);
+        max_y = Math::clamp(max_y, 0, size.y);
+    }
+
+    inline void pad(int p) {
+        min_x -= p;
+        min_y -= p;
+        max_x += p;
+        max_y += p;
+    }
+
+    inline int get_width() const {
+        return max_x - min_x;
+    }
+
+    inline int get_height() const {
+        return max_y - min_y;
+    }
+};
+
+#endif // INT_RANGE_2D_H

addons/zylann.hterrain/native/src/math_funcs.h

@@ -0,0 +1,28 @@
+#ifndef MATH_FUNCS_H
+#define MATH_FUNCS_H
+
+namespace Math {
+
+inline float lerp(float minv, float maxv, float t) {
+    return minv + t * (maxv - minv);
+}
+
+template <typename T>
+inline T clamp(T x, T minv, T maxv) {
+    if (x < minv) {
+        return minv;
+    }
+    if (x > maxv) {
+        return maxv;
+    }
+    return x;
+}
+
+template <typename T>
+inline T min(T a, T b) {
+    return a < b ? a : b;
+}
+
+} // namespace Math
+
+#endif // MATH_FUNCS_H

addons/zylann.hterrain/native/src/quad_tree_lod.cpp

@@ -0,0 +1,242 @@
+#include "quad_tree_lod.h"
+
+namespace godot {
+
+void QuadTreeLod::set_callbacks(Ref<FuncRef> make_cb, Ref<FuncRef> recycle_cb, Ref<FuncRef> vbounds_cb) {
+	_make_func = make_cb;
+	_recycle_func = recycle_cb;
+	_vertical_bounds_func = vbounds_cb;
+}
+
+int QuadTreeLod::get_lod_count() {
+	// TODO make this a count, not max
+	return _max_depth + 1;
+}
+
+int QuadTreeLod::get_lod_factor(int lod) {
+	return 1 << lod;
+}
+
+int QuadTreeLod::compute_lod_count(int base_size, int full_size) {
+	int po = 0;
+	while (full_size > base_size) {
+		full_size = full_size >> 1;
+		po += 1;
+	}
+	return po;
+}
+
+// The higher, the longer LODs will spread and higher the quality.
+// The lower, the shorter LODs will spread and lower the quality.
+void QuadTreeLod::set_split_scale(real_t p_split_scale) {
+	real_t MIN = 2.0f;
+	real_t MAX = 5.0f;
+
+	// Split scale must be greater than a threshold,
+	// otherwise lods will decimate too fast and it will look messy
+	if (p_split_scale < MIN)
+		p_split_scale = MIN;
+	if (p_split_scale > MAX)
+		p_split_scale = MAX;
+
+	_split_scale = p_split_scale;
+}
+
+real_t QuadTreeLod::get_split_scale() {
+	return _split_scale;
+}
+
+void QuadTreeLod::clear() {
+	_join_all_recursively(ROOT, _max_depth);
+	_max_depth = 0;
+	_base_size = 0;
+}
+
+void QuadTreeLod::create_from_sizes(int base_size, int full_size) {
+	clear();
+	_base_size = base_size;
+	_max_depth = compute_lod_count(base_size, full_size);
+
+	// Total qty of nodes is (N^L - 1) / (N - 1). -1 for root, where N=num children, L=levels including the root
+	int node_count = ((static_cast<int>(pow(4, _max_depth+1)) - 1) / (4 - 1)) - 1;
+	_node_pool.resize(node_count); // e.g. ((4^6 -1) / 3 ) - 1 = 1364 excluding root
+
+	_free_indices.resize((node_count / 4)); // 1364 / 4 = 341
+	for (int i = 0; i < _free_indices.size(); i++) // i = 0 to 340, *4 = 0 to 1360
+		_free_indices[i] = 4 * i; // _node_pool[4*0 + i0] is first child, [4*340 + i3] is last
+}
+
+void QuadTreeLod::update(Vector3 view_pos) {
+	_update(ROOT, _max_depth, view_pos);
+
+	// This makes sure we keep seeing the lowest LOD,
+	// if the tree is cleared while we are far away
+	Quad *root = _get_root();
+	if (!root->has_children() && root->is_null())
+		root->set_data(_make_chunk(_max_depth, 0, 0));
+}
+
+void QuadTreeLod::debug_draw_tree(CanvasItem *ci) {
+	if (ci != nullptr)
+		_debug_draw_tree_recursive(ci, ROOT, _max_depth, 0);
+}
+
+// Intention is to only clear references to children
+void QuadTreeLod::_clear_children(unsigned int index) {
+	Quad *quad = _get_node(index);
+	if (quad->has_children()) {
+		_recycle_children(quad->first_child);
+		quad->first_child = NO_CHILDREN;
+	}
+}
+
+// Returns the index of the first_child. Allocates from _free_indices.
+unsigned int QuadTreeLod::_allocate_children() {
+	if (_free_indices.size() == 0) {
+		return NO_CHILDREN;
+	}
+
+	unsigned int i0 = _free_indices[_free_indices.size() - 1];
+	_free_indices.pop_back();
+	return i0;
+}
+
+// Pass the first_child index, not the parent index. Stores back in _free_indices.
+void QuadTreeLod::_recycle_children(unsigned int i0) {
+	// Debug check, there is no use case in recycling a node which is not a first child
+	CRASH_COND(i0 % 4 != 0);
+
+	for (int i = 0; i < 4; ++i) {
+		_node_pool[i0 + i].init();
+	}
+
+	_free_indices.push_back(i0);
+}
+
+Variant QuadTreeLod::_make_chunk(int lod, int origin_x, int origin_y) {
+	if (_make_func.is_valid()) {
+		return _make_func->call_func(origin_x, origin_y, lod);
+	} else {
+		return Variant();
+	}
+}
+
+void QuadTreeLod::_recycle_chunk(unsigned int quad_index, int lod) {
+	Quad *quad = _get_node(quad_index);
+	if (_recycle_func.is_valid()) {
+		_recycle_func->call_func(quad->get_data(), quad->origin_x, quad->origin_y, lod);
+	}
+}
+
+void QuadTreeLod::_join_all_recursively(unsigned int quad_index, int lod) {
+	Quad *quad = _get_node(quad_index);
+
+	if (quad->has_children()) {
+		for (int i = 0; i < 4; i++) {
+			_join_all_recursively(quad->first_child + i, lod - 1);
+		}
+		_clear_children(quad_index);
+
+	} else if (quad->is_valid()) {
+		_recycle_chunk(quad_index, lod);
+		quad->clear_data();
+	}
+}
+
+void QuadTreeLod::_update(unsigned int quad_index, int lod, Vector3 view_pos) {
+	// This function should be called regularly over frames.
+	Quad *quad = _get_node(quad_index);
+	int lod_factor = get_lod_factor(lod);
+	int chunk_size = _base_size * lod_factor;
+	Vector3 world_center = static_cast<real_t>(chunk_size) * (Vector3(static_cast<real_t>(quad->origin_x), 0.f, static_cast<real_t>(quad->origin_y)) + Vector3(0.5f, 0.f, 0.5f));
+
+	if (_vertical_bounds_func.is_valid()) {
+		Variant result = _vertical_bounds_func->call_func(quad->origin_x, quad->origin_y, lod);
+		ERR_FAIL_COND(result.get_type() != Variant::VECTOR2);
+		Vector2 vbounds = static_cast<Vector2>(result);
+		world_center.y = (vbounds.x + vbounds.y) / 2.0f;
+	}
+
+	int split_distance = _base_size * lod_factor * static_cast<int>(_split_scale);
+
+	if (!quad->has_children()) {
+		if (lod > 0 && world_center.distance_to(view_pos) < split_distance) {
+			// Split
+			unsigned int new_idx = _allocate_children();
+			ERR_FAIL_COND(new_idx == NO_CHILDREN);
+			quad->first_child = new_idx;
+
+			for (int i = 0; i < 4; i++) {
+				Quad *child = _get_node(quad->first_child + i);
+				child->origin_x = quad->origin_x * 2 + (i & 1);
+				child->origin_y = quad->origin_y * 2 + ((i & 2) >> 1);
+				child->set_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->is_valid()) {
+				_recycle_chunk(quad_index, lod);
+				quad->clear_data();
+			}
+		}
+	} else {
+		bool no_split_child = true;
+
+		for (int i = 0; i < 4; i++) {
+			_update(quad->first_child + i, lod - 1, view_pos);
+
+			if (_get_node(quad->first_child + i)->has_children())
+				no_split_child = false;
+		}
+
+		if (no_split_child && world_center.distance_to(view_pos) > split_distance) {
+			// Join
+			for (int i = 0; i < 4; i++) {
+				_recycle_chunk(quad->first_child + i, lod - 1);
+			}
+			_clear_children(quad_index);
+			quad->set_data(_make_chunk(lod, quad->origin_x, quad->origin_y));
+		}
+	}
+} // _update
+
+void QuadTreeLod::_debug_draw_tree_recursive(CanvasItem *ci, unsigned int quad_index, int lod_index, int child_index) {
+	Quad *quad = _get_node(quad_index);
+
+	if (quad->has_children()) {
+		int ch_index = quad->first_child;
+		for (int i = 0; i < 4; i++) {
+			_debug_draw_tree_recursive(ci, ch_index + i, lod_index - 1, i);
+		}
+
+	} else {
+		real_t size = static_cast<real_t>(get_lod_factor(lod_index));
+		int checker = 0;
+		if (child_index == 1 || child_index == 2)
+			checker = 1;
+
+		int chunk_indicator = 0;
+		if (quad->is_valid())
+			chunk_indicator = 1;
+
+		Rect2 rect2(Vector2(static_cast<real_t>(quad->origin_x), static_cast<real_t>(quad->origin_y)) * size,
+				Vector2(size, size));
+		Color color(1.0f - static_cast<real_t>(lod_index) * 0.2f, 0.2f * static_cast<real_t>(checker), static_cast<real_t>(chunk_indicator), 1.0f);
+		ci->draw_rect(rect2, color);
+	}
+}
+
+void QuadTreeLod::_register_methods() {
+	register_method("set_callbacks", &QuadTreeLod::set_callbacks);
+	register_method("get_lod_count", &QuadTreeLod::get_lod_count);
+	register_method("get_lod_factor", &QuadTreeLod::get_lod_factor);
+	register_method("compute_lod_count", &QuadTreeLod::compute_lod_count);
+	register_method("set_split_scale", &QuadTreeLod::set_split_scale);
+	register_method("get_split_scale", &QuadTreeLod::get_split_scale);
+	register_method("clear", &QuadTreeLod::clear);
+	register_method("create_from_sizes", &QuadTreeLod::create_from_sizes);
+	register_method("update", &QuadTreeLod::update);
+	register_method("debug_draw_tree", &QuadTreeLod::debug_draw_tree);
+}
+
+} // namespace godot

addons/zylann.hterrain/native/src/quad_tree_lod.h

@@ -0,0 +1,121 @@
+#ifndef QUAD_TREE_LOD_H
+#define QUAD_TREE_LOD_H
+
+#include <CanvasItem.hpp>
+#include <FuncRef.hpp>
+#include <Godot.hpp>
+
+#include <vector>
+
+namespace godot {
+
+class QuadTreeLod : public Reference {
+	GODOT_CLASS(QuadTreeLod, Reference)
+public:
+	static void _register_methods();
+
+	QuadTreeLod() {}
+	~QuadTreeLod() {}
+	
+	void _init() {}
+
+	void set_callbacks(Ref<FuncRef> make_cb, Ref<FuncRef> recycle_cb, Ref<FuncRef> vbounds_cb);
+	int get_lod_count();
+	int get_lod_factor(int lod);
+	int compute_lod_count(int base_size, int full_size);
+	void set_split_scale(real_t p_split_scale);
+	real_t get_split_scale();
+	void clear();
+	void create_from_sizes(int base_size, int full_size);
+	void update(Vector3 view_pos);
+	void debug_draw_tree(CanvasItem *ci);
+
+private:
+	static const unsigned int NO_CHILDREN = -1;
+	static const unsigned int ROOT = -1;
+
+	class Quad {
+	public:
+		unsigned int first_child = NO_CHILDREN;
+		int origin_x = 0;
+		int origin_y = 0;
+
+		Quad() {
+			init();
+		}
+
+		~Quad() {
+		}
+
+		inline void init() {
+			first_child = NO_CHILDREN;
+			origin_x = 0;
+			origin_y = 0;
+			clear_data();
+		}
+
+		inline void clear_data() {
+			_data = Variant();
+		}
+
+		inline bool has_children() {
+			return first_child != NO_CHILDREN;
+		}
+
+		inline bool is_null() {
+			return _data.get_type() == Variant::NIL;
+		}
+
+		inline bool is_valid() {
+			return _data.get_type() != Variant::NIL;
+		}
+
+		inline Variant get_data() {
+			return _data;
+		}
+
+		inline void set_data(Variant p_data) {
+			_data = p_data;
+		}
+
+	private:
+		Variant _data; // Type is HTerrainChunk.gd : Object
+	};
+
+	Quad _root;
+	std::vector<Quad> _node_pool;
+	std::vector<unsigned int> _free_indices;
+
+	int _max_depth = 0;
+	int _base_size = 16;
+	real_t _split_scale = 2.0f;
+
+	Ref<FuncRef> _make_func;
+	Ref<FuncRef> _recycle_func;
+	Ref<FuncRef> _vertical_bounds_func;
+
+	inline Quad *_get_root() {
+		return &_root;
+	}
+
+	inline Quad *_get_node(unsigned int index) {
+		if (index == ROOT) {
+			return &_root;
+		} else {
+			return &_node_pool[index];
+		}
+	}
+
+	void _clear_children(unsigned int index);
+	unsigned int _allocate_children();
+	void _recycle_children(unsigned int i0);
+	Variant _make_chunk(int lod, int origin_x, int origin_y);
+	void _recycle_chunk(unsigned int quad_index, int lod);
+	void _join_all_recursively(unsigned int quad_index, int lod);
+	void _update(unsigned int quad_index, int lod, Vector3 view_pos);
+	void _debug_draw_tree_recursive(CanvasItem *ci, unsigned int quad_index, int lod_index, int child_index);
+}; // class QuadTreeLod
+
+} // namespace godot
+
+#endif // QUAD_TREE_LOD_H

addons/zylann.hterrain/native/src/vector2i.h

@@ -0,0 +1,19 @@
+#ifndef VECTOR2I_H
+#define VECTOR2I_H
+
+#include <core/Vector2.hpp>
+
+struct Vector2i {
+    int x;
+    int y;
+
+    Vector2i(godot::Vector2 v) :
+            x(static_cast<int>(v.x)),
+            y(static_cast<int>(v.y)) {}
+
+    bool any_zero() const {
+        return x == 0 || y == 0;
+    }
+};
+
+#endif // VECTOR2I_H