From 95c346497371395b401be2c9e4e37c8eaa3c8c60 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Wed, 3 Aug 2016 12:17:22 +0200
Subject: [PATCH] - properly handle 3D floors with inverted planes in the list
 sorter.

---
 src/p_3dfloors.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/p_3dfloors.cpp b/src/p_3dfloors.cpp
index 5e2117b9b..d27ebe4d1 100644
--- a/src/p_3dfloors.cpp
+++ b/src/p_3dfloors.cpp
@@ -514,6 +514,17 @@ void P_Recalculate3DFloors(sector_t * sector)
 						clipped_bottom = pick_bottom;
 					}
 				}
+				else if (pick_bottom > height)	// do not allow inverted planes
+				{
+					F3DFloor * dyn = new F3DFloor;
+					*dyn = *pick;
+					pick->flags |= FF_CLIPPED;
+					pick->flags &= ~FF_EXISTS;
+					dyn->flags |= FF_DYNAMIC;
+					dyn->bottom.copyPlane(&pick->top);
+					ffloors.Push(pick);
+					ffloors.Push(dyn);
+				}
 				else
 				{
 					clipped = pick;