From db944df467a49e64fbbbad9bdae70f88802d2799 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Sun, 22 May 2016 12:15:14 +0200
Subject: [PATCH] - fixed 3D floor rendering with nearby slopes.

---
 src/r_bsp.cpp | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/r_bsp.cpp b/src/r_bsp.cpp
index f41e99a74..934d2d3e5 100644
--- a/src/r_bsp.cpp
+++ b/src/r_bsp.cpp
@@ -622,6 +622,18 @@ void R_AddLine (seg_t *line)
 		rw_backcz2 = backsector->ceilingplane.ZatPoint(line->v2);
 		rw_backfz2 = backsector->floorplane.ZatPoint(line->v2);
 
+		if (fake3D & FAKE3D_FAKEBACK)
+		{
+			if (rw_frontfz1 >= rw_backfz1 && rw_frontfz2 >= rw_backfz2)
+			{
+				fake3D |= FAKE3D_CLIPBOTFRONT;
+			}
+			if (rw_frontcz1 <= rw_backcz1 && rw_frontcz2 <= rw_backcz2)
+			{
+				fake3D |= FAKE3D_CLIPTOPFRONT;
+			}
+		}
+
 		// Cannot make these walls solid, because it can result in
 		// sprite clipping problems for sprites near the wall
 		if (rw_frontcz1 > rw_backcz1 || rw_frontcz2 > rw_backcz2)
@@ -1334,14 +1346,6 @@ void R_Subsector (subsector_t *sub)
 						fakeFloor->validcount = validcount;
 						R_3D_NewClip();
 					}
-					if (frontsector->CenterFloor() >= backsector->CenterFloor())
-					{
-						fake3D |= FAKE3D_CLIPBOTFRONT;
-					}
-					if (frontsector->CenterCeiling() <= backsector->CenterCeiling())
-					{
-						fake3D |= FAKE3D_CLIPTOPFRONT;
-					}
 					R_AddLine(line); // fake
 				}
 				fakeFloor = NULL;