diff --git a/src/p_local.h b/src/p_local.h
index f99cace17..12f98a4b8 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -347,6 +347,7 @@ public:
 #define PT_ADDLINES 	1
 #define PT_ADDTHINGS	2
 #define PT_COMPATIBLE	4
+#define PT_DELTA		8		// x2,y2 is passed as a delta, not as an endpoint
 
 AActor *P_BlockmapSearch (AActor *mo, int distance, AActor *(*check)(AActor*, int, void *), void *params = NULL);
 AActor *P_RoughMonsterSearch (AActor *mo, int distance);
diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index 24d4337e3..6887425e3 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -1165,10 +1165,9 @@ intercept_t *FPathTraverse::Next()
 
 FPathTraverse::FPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2, int flags)
 {
-	fixed_t 	xt1;
-	fixed_t 	yt1;
-	fixed_t 	xt2;
-	fixed_t 	yt2;
+	fixed_t 	xt1, xt2;
+	fixed_t 	yt1, yt2;
+	long long	_x1, _x2, _y1, _y2;
 	
 	fixed_t 	xstep;
 	fixed_t 	ystep;
@@ -1197,18 +1196,42 @@ FPathTraverse::FPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2, in
 
 	trace.x = x1;
 	trace.y = y1;
-	trace.dx = x2 - x1;
-	trace.dy = y2 - y1;
+	if (flags & PT_DELTA)
+	{
+		trace.dx = x2;
+		trace.dy = y2;
+	}
+	else
+	{
+		trace.dx = x2 - x1;
+		trace.dy = y2 - y1;
+	}
 
+	_x1 = (long long)x1 - bmaporgx;
+	_y1 = (long long)y1 - bmaporgy;
 	x1 -= bmaporgx;
 	y1 -= bmaporgy;
-	xt1 = GetSafeBlockX(x1);
-	yt1 = GetSafeBlockY(y1);
+	xt1 = int(_x1 >> MAPBLOCKSHIFT);
+	yt1 = int(_y1 >> MAPBLOCKSHIFT);
 
-	x2 -= bmaporgx;
-	y2 -= bmaporgy;
-	xt2 = GetSafeBlockX(x2);
-	yt2 = GetSafeBlockY(y2);
+	if (flags & PT_DELTA)
+	{
+		_x2 = _x1 + x2;
+		_y2 = _y1 + y2;
+		xt2 = int(_x2 >> MAPBLOCKSHIFT);
+		yt2 = int(_y2 >> MAPBLOCKSHIFT);
+		x2 = (int)_x2;
+		y2 = (int)_y2;
+	}
+	else
+	{
+		_x2 = (long long)x2 - bmaporgx;
+		_y2 = (long long)y2 - bmaporgy;
+		x2 -= bmaporgx;
+		y2 -= bmaporgy;
+		xt2 = int(_x2 >> MAPBLOCKSHIFT);
+		yt2 = int(_y2 >> MAPBLOCKSHIFT);
+	}
 
 	if (xt2 > xt1)
 	{
@@ -1228,7 +1251,7 @@ FPathTraverse::FPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2, in
 		partialx = FRACUNIT;
 		ystep = 256*FRACUNIT;
 	}	
-	yintercept = (y1>>MAPBTOFRAC) + FixedMul (partialx, ystep);
+	yintercept = int(_y1>>MAPBTOFRAC) + FixedMul (partialx, ystep);
 
 		
 	if (yt2 > yt1)
@@ -1249,7 +1272,7 @@ FPathTraverse::FPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2, in
 		partialy = FRACUNIT;
 		xstep = 256*FRACUNIT;
 	}	
-	xintercept = (x1>>MAPBTOFRAC) + FixedMul (partialy, xstep);
+	xintercept = int(_x1>>MAPBTOFRAC) + FixedMul (partialy, xstep);
 
 	// [RH] Fix for traces that pass only through blockmap corners. In that case,
 	// xintercept and yintercept can both be set ahead of mapx and mapy, so the
diff --git a/src/p_sight.cpp b/src/p_sight.cpp
index a91415486..ef4dfacd0 100644
--- a/src/p_sight.cpp
+++ b/src/p_sight.cpp
@@ -443,6 +443,7 @@ bool SightCheck::P_SightTraverseIntercepts ()
 bool SightCheck::P_SightPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_t y2)
 {
 	fixed_t xt1,yt1,xt2,yt2;
+	long long _x1,_y1,_x2,_y2;
 	fixed_t xstep,ystep;
 	fixed_t partialx, partialy;
 	fixed_t xintercept, yintercept;
@@ -482,15 +483,19 @@ bool SightCheck::P_SightPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_
 	trace.dx = x2 - x1;
 	trace.dy = y2 - y1;
 
+	_x1 = (long long)x1 - bmaporgx;
+	_y1 = (long long)y1 - bmaporgy;
 	x1 -= bmaporgx;
 	y1 -= bmaporgy;
-	xt1 = GetSafeBlockX(x1);
-	yt1 = GetSafeBlockY(y1);
+	xt1 = int(_x1 >> MAPBLOCKSHIFT);
+	yt1 = int(_y1 >> MAPBLOCKSHIFT);
 
+	_x2 = (long long)x2 - bmaporgx;
+	_y2 = (long long)y2 - bmaporgy;
 	x2 -= bmaporgx;
 	y2 -= bmaporgy;
-	xt2 = GetSafeBlockX(x2);
-	yt2 = GetSafeBlockY(y2);
+	xt2 = int(_x2 >> MAPBLOCKSHIFT);
+	yt2 = int(_y2 >> MAPBLOCKSHIFT);
 
 // points should never be out of bounds, but check once instead of
 // each block
@@ -516,7 +521,7 @@ bool SightCheck::P_SightPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_
 		partialx = FRACUNIT;
 		ystep = 256*FRACUNIT;
 	}
-	yintercept = (y1>>MAPBTOFRAC) + FixedMul (partialx, ystep);
+	yintercept = int(_y1>>MAPBTOFRAC) + FixedMul (partialx, ystep);
 
 
 	if (yt2 > yt1)
@@ -537,7 +542,7 @@ bool SightCheck::P_SightPathTraverse (fixed_t x1, fixed_t y1, fixed_t x2, fixed_
 		partialy = FRACUNIT;
 		xstep = 256*FRACUNIT;
 	}
-	xintercept = (x1>>MAPBTOFRAC) + FixedMul (partialy, xstep);
+	xintercept = int(_x1>>MAPBTOFRAC) + FixedMul (partialy, xstep);
 
 	// [RH] Fix for traces that pass only through blockmap corners. In that case,
 	// xintercept and yintercept can both be set ahead of mapx and mapy, so the
diff --git a/src/p_trace.cpp b/src/p_trace.cpp
index 59dbe08f9..93c347d9f 100644
--- a/src/p_trace.cpp
+++ b/src/p_trace.cpp
@@ -175,19 +175,19 @@ bool Trace (fixed_t x, fixed_t y, fixed_t z, sector_t *sector,
 #endif
 
 	// check for overflows and clip if necessary
-	SQWORD xd= (SQWORD)x + ( ( SQWORD(vx) * SQWORD(maxDist) )>>16);
+	SQWORD xd = (SQWORD)x + ( ( SQWORD(vx) * SQWORD(maxDist) )>>16);
 
 	if (xd>SQWORD(32767)*FRACUNIT)
 	{
-		maxDist = inf.MaxDist=FixedDiv(FIXED_MAX-x,vx);
+		maxDist = inf.MaxDist = FixedDiv(FIXED_MAX - x, vx);
 	}
 	else if (xd<-SQWORD(32767)*FRACUNIT)
 	{
-		maxDist = inf.MaxDist=FixedDiv(FIXED_MIN-x,vx);
+		maxDist = inf.MaxDist = FixedDiv(FIXED_MIN - x, vx);
 	}
 
 
-	SQWORD yd= (SQWORD)y + ( ( SQWORD(vy) * SQWORD(maxDist) )>>16);
+	SQWORD yd = (SQWORD)y + ( ( SQWORD(vy) * SQWORD(maxDist) )>>16);
 
 	if (yd>SQWORD(32767)*FRACUNIT)
 	{
@@ -246,7 +246,7 @@ bool Trace (fixed_t x, fixed_t y, fixed_t z, sector_t *sector,
 
 bool FTraceInfo::TraceTraverse (int ptflags)
 {
-	FPathTraverse it(StartX, StartY, StartX + FixedMul (Vx, MaxDist), StartY + FixedMul (Vy, MaxDist), ptflags);
+	FPathTraverse it(StartX, StartY, FixedMul (Vx, MaxDist), FixedMul (Vy, MaxDist), ptflags | PT_DELTA);
 	intercept_t *in;
 
 	while ((in = it.Next()))