Selects all polygons which face straight up and are at or below 0 in the Y axis.

selectGroundPolys.py

#!/usr/bin/env python
 
import lx
import lxifc
import lxu.command

class SelectGround(lxifc.Visitor):
	def __init__(self, poly, mesh):
		self.poly = poly
		self.mesh = mesh

		self.sel_svc = lx.service.Selection()
		self.sel_type_polygon = self.sel_svc.LookupType(lx.symbol.sSELTYP_POLYGON)
		self.trans = lx.object.PolygonPacketTranslation(self.sel_svc.Allocate(lx.symbol.sSELTYP_POLYGON))

	def vis_Evaluate(self):
		if self.poly.Normal()[1] > 0.999 and self.poly.RepresentativePosition()[1] <= 0.01:
			sel_pkt = self.trans.Packet(self.poly.ID(), self.mesh)
			self.sel_svc.Select(self.sel_type_polygon, sel_pkt)

class SelectGround_Cmd(lxu.command.BasicCommand):

	def __init__(self):
		lxu.command.BasicCommand.__init__(self)

	def cmd_UserName(self):
 		return 'Select Ground Polys'

	def basic_ButtonName(self):
		return 'Select Ground Polys'

 	def cmd_Desc(self):
 		return 'Select all polyons at or below ground level which face upwards'

 	def cmd_Tooltip(self):
 		return 'Select all polyons at or below ground level which face upwards'

 	def cmd_Help(self):
 		return 'https://farfarer.com'
 
	def cmd_Flags(self):
		return lx.symbol.fCMD_UNDO | lx.symbol.fCMD_SELECT

	def basic_Enable(self, msg):
		return True

	def cmd_Interact(self):
		pass

	def basic_Execute(self, msg, flags):
		layer_svc = lx.service.Layer()
		layer_scan = lx.object.LayerScan(layer_svc.ScanAllocate(lx.symbol.f_LAYERSCAN_ACTIVE))
		if not layer_scan.test():
			return

		layer_count = layer_scan.Count()
		if layer_count == 0:
			return

		sel_svc = lx.service.Selection()

		# If you don't want to drop the current polygon selection first, remove the following line.
		sel_svc.Drop(sel_svc.LookupType(lx.symbol.sSELTYP_POLYGON))

		sel_svc.StartBatch()

		for layer_idx in xrange(layer_count):
			mesh = lx.object.Mesh(layer_scan.MeshBase(layer_idx))
			if not mesh.test():
				continue

			polygon_count = mesh.PolygonCount()
			if polygon_count == 0:
				continue

			polygon = mesh.PolygonAccessor()
			if not polygon.test():
				continue

			selectGround = SelectGround(polygon, mesh)
			polygon.Enumerate(lx.symbol.iMARK_ANY, selectGround, 0)

		layer_scan.Apply()

		sel_svc.EndBatch()

lx.bless(SelectGround_Cmd, 'ffr.selectGroundPolys')