Added automatic procedural level of detail to planets

godot/Scripts/PlanetGeneration/QuadTreeNode.gd

@@ -0,0 +1,184 @@
+extends Node
+class_name QuadTreeNode
+
+var is_root : bool = false:
+	get:
+		return is_root
+	set(value):
+		is_root = value
+
+var is_leaf : bool = true:
+	get:
+		return is_leaf
+	set(value):
+		is_leaf = value
+
+var level : int
+var radius : float = 1.0
+
+var children : Array
+
+var mesh_instance : MeshInstance3D = MeshInstance3D.new()
+
+var material = load("res://PlanetColoring.tres")
+
+@export var normal : Vector3
+@export var center : Vector2
+
+var center_of_mass : Vector3
+
+const THRESHOLDS = [512*512, 128*128, 64*64, 32*32]
+const RESOLUTION = 17
+
+func split(planet_data : PlanetData):
+	remove_child(mesh_instance)
+	mesh_instance = null
+
+	children[0] = QuadTreeNode.new()
+	children[0].center = center + Vector2(radius/2, radius/2)
+
+	children[1] = QuadTreeNode.new()
+	children[1].center = center + Vector2(-radius/2, radius/2)
+
+	children[2] = QuadTreeNode.new()
+	children[2].center = center + Vector2(radius/2, -radius/2)
+
+	children[3] = QuadTreeNode.new()
+	children[3].center = center + Vector2(-radius/2, -radius/2)
+
+	for child in children:
+		call_deferred("add_child", child)
+		child.level = level + 1
+		child.radius = radius/2
+		child.normal = normal
+		child.material = material
+		child.mesh_instance = MeshInstance3D.new()
+		child.regenerate_mesh(planet_data)
+		child.call_deferred("add_child", child.mesh_instance)
+	
+	self.is_leaf = false
+
+func join():
+	for child in children:
+		if (child != null):
+			child.join()
+			child.free()
+			child = null
+	self.is_leaf = true
+	mesh_instance = MeshInstance3D.new()
+	call_deferred("add_child", mesh_instance)
+	
+
+func update_from_camera_pos(planet_data : PlanetData, camera : Camera3D = null):
+	if (camera == null):
+		camera = get_viewport().get_camera_3d()
+	if (camera == null):
+		return
+	var camera_pos = camera.global_position
+	
+	var dist = (camera_pos - center_of_mass).length_squared()
+	
+	if (self.level < (THRESHOLDS.size() - 1) and dist < THRESHOLDS[self.level] and self.is_leaf):
+		split(planet_data)
+	elif (dist > THRESHOLDS[self.level] + 4 and not self.is_leaf):
+		join()
+		regenerate_mesh(planet_data)
+
+	if (children[0] != null):
+		for child in children:
+			child.update_from_camera_pos(planet_data, camera)
+	
+func regenerate_mesh(planet_data):
+	var arrays := []
+	arrays.resize(Mesh.ARRAY_MAX)
+	
+	var vertex_array := PackedVector3Array()
+	var uv_array := PackedVector2Array()
+	var normal_array := PackedVector3Array()
+	
+	var index_array := PackedInt32Array()
+	var num_vertices : int = RESOLUTION * RESOLUTION
+	var num_indices : int = (RESOLUTION-1) * (RESOLUTION-1) * 6
+	
+	vertex_array.resize(num_vertices)
+	normal_array.resize(num_vertices)
+	uv_array.resize(num_vertices)
+	index_array.resize(num_indices)
+	
+	var tri_index : int = 0
+	var a_axis := Vector3(normal.y, normal.z, normal.x)
+	var b_axis : Vector3 = normal.cross(a_axis)
+	for y in range(RESOLUTION):
+		for x in range(RESOLUTION):
+			var i : int = x + y*RESOLUTION
+			
+			# Relative position of the current point inside the tile
+			var percent := Vector2(x,y) / (RESOLUTION-1)
+			
+			# Calculate the point on a cube, normalize it to a sphere, and map it to a point on the planet's surface.
+			var point_on_cube : Vector3 = normal + (center.x + (percent.x - 0.5)*2.0*radius)*a_axis + (center.y + (percent.y - 0.5)*2.0*radius)*b_axis
+			var point_on_sphere = point_on_cube.normalized()
+			var point_on_planet = planet_data.point_on_planet(point_on_sphere)
+			
+			# Update the max and min elevations of the planet's surface.
+			var elevation = point_on_planet.length()
+			if (elevation < planet_data.min_elevation):
+				planet_data.min_elevation = elevation
+			if (elevation > planet_data.max_elevation):
+				planet_data.max_elevation = elevation
+				
+			# Calculate center of mass of current tile.
+			if (percent.x == 0.5 and percent.y == 0.5):
+				center_of_mass = point_on_planet
+
+			vertex_array[i] = point_on_planet
+			if x != RESOLUTION-1 and y != RESOLUTION-1:
+				index_array[tri_index + 2] = i
+				index_array[tri_index + 1] = i+RESOLUTION+1
+				index_array[tri_index] = i+RESOLUTION
+				
+				index_array[tri_index + 5] = i
+				index_array[tri_index + 4] = i+1
+				index_array[tri_index + 3] = i+RESOLUTION+1
+				tri_index += 6
+	
+	for a in range(0, index_array.size(), 3):
+		var b : int = a + 1
+		var c : int = a + 2
+
+		var ab : Vector3 = vertex_array[index_array[b]] - vertex_array[index_array[a]]
+		var bc : Vector3 = vertex_array[index_array[c]] - vertex_array[index_array[b]]
+		var ca : Vector3 = vertex_array[index_array[a]] - vertex_array[index_array[c]]
+		
+		var cross_ab_bc : Vector3 = bc.cross(ab)
+		var cross_bc_ca : Vector3 = ca.cross(bc)
+		var cross_ca_ab : Vector3 = ab.cross(ca)
+
+		normal_array[index_array[a]] += cross_ab_bc + cross_bc_ca + cross_ca_ab
+		normal_array[index_array[b]] += cross_ab_bc + cross_bc_ca + cross_ca_ab
+		normal_array[index_array[c]] += cross_ab_bc + cross_bc_ca + cross_ca_ab
+
+	for i in range(normal_array.size()):
+		normal_array[i] = normal_array[i].normalized()
+
+	arrays[Mesh.ARRAY_VERTEX] = vertex_array
+	arrays[Mesh.ARRAY_NORMAL] = normal_array
+	arrays[Mesh.ARRAY_TEX_UV] = uv_array
+	arrays[Mesh.ARRAY_INDEX] = index_array
+
+	call_deferred("_update_mesh", arrays, planet_data)
+
+func _update_mesh(arrays : Array, planet_data):
+	var _mesh := ArrayMesh.new()
+	_mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)		
+	if (mesh_instance == null):
+		return
+		
+	mesh_instance.mesh = _mesh
+	mesh_instance.material_override = material
+	mesh_instance.material_override.set_shader_parameter("min_elevation", planet_data.min_elevation - 0.2)
+	mesh_instance.material_override.set_shader_parameter("max_elevation", planet_data.max_elevation)
+	mesh_instance.material_override.set_shader_parameter("elevation_color", planet_data.planet_color)
+
+func _init():
+	children.resize(4)