Subdivided Plane Set as Lod Levels in Godot 4.0

generate_plane.gd

@tool
extends MeshInstance3D

@export var generate := false:
	set(v):
		gen_mesh()

@export_range(0, 10) var subdivisions := 5
@export var size := 8.0

func gen_mesh():
	print("gen mesh")
	
	var new_mesh := ArrayMesh.new()
	var verts := PackedVector3Array()
	var indices := []
	
	var index_counter := 0
	
	var lod := subdivisions
	
	while lod >= 0:
		var subs = pow(2.0, float(lod))
		var sub_indices := PackedInt32Array()
		for y in subs:
			for x in subs:
				
				var current_pos := Vector3()
				
				verts.append(Vector3(float(x) / subs * size, 0.0, float(y) / subs * size))
				verts.append(Vector3(float(x) / subs * size + float(size) / subs, 0.0, float(y) / subs * size))
				verts.append(Vector3(float(x) / subs * size, 0.0, float(y) / subs * size + float(size) / subs))
				verts.append(Vector3(float(x) / subs * size, 0.0, float(y) / subs * size + float(size) / subs))
				verts.append(Vector3(float(x) / subs * size + float(size) / subs, 0.0, float(y) / subs * size))
				verts.append(Vector3(float(x) / subs * size + float(size) / subs, 0.0, float(y) / subs * size + float(size) / subs))
				
				sub_indices.append(index_counter)
				sub_indices.append(index_counter + 1)
				sub_indices.append(index_counter + 2)
				sub_indices.append(index_counter + 3)
				sub_indices.append(index_counter + 4)
				sub_indices.append(index_counter + 5)
				index_counter += 6;
		
		indices.append(sub_indices)
		lod -= 1
	
	var vertices := PackedVector3Array(verts)
	
	var arrays = []
	arrays.resize(Mesh.ARRAY_MAX)
	arrays[Mesh.ARRAY_VERTEX] = verts
	arrays[Mesh.ARRAY_INDEX] = indices[0]
	var blend_shapes = []
	
	var lods = {}
	for i in subdivisions:
		lods[(float(i) + 1.0)] = indices[i + 1]
	
	new_mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays, blend_shapes, lods)
	mesh = new_mesh