diff --git a/src/p_setup.c b/src/p_setup.c
index eedda1b08..2533ae9f9 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3009,7 +3009,7 @@ static inline void P_LoadSubsectors(UINT8 *data)
 	for (i = 0; i < numsubsectors; i++, ss++, ms++)
 	{
 		ss->numlines = SHORT(ms->numsegs);
-		ss->firstline = SHORT(ms->firstseg);
+		ss->firstline = (UINT16)SHORT(ms->firstseg);
 		P_InitializeSubsector(ss);
 	}
 }
diff --git a/src/r_bsp.c b/src/r_bsp.c
index bf238a435..c9c169a51 100644
--- a/src/r_bsp.c
+++ b/src/r_bsp.c
@@ -399,8 +399,8 @@ static void R_AddLine(seg_t *line)
 		return;
 
 	// big room fix
-	angle1 = R_PointToAngleEx(viewx, viewy, line->v1->x, line->v1->y);
-	angle2 = R_PointToAngleEx(viewx, viewy, line->v2->x, line->v2->y);
+	angle1 = R_PointToAngle64(line->v1->x, line->v1->y);
+	angle2 = R_PointToAngle64(line->v2->x, line->v2->y);
 	curline = line;
 
 	// Clip to view edges.
@@ -620,8 +620,8 @@ static boolean R_CheckBBox(const fixed_t *bspcoord)
 	check = checkcoord[boxpos];
 
 	// big room fix
-	angle1 = R_PointToAngleEx(viewx, viewy, bspcoord[check[0]], bspcoord[check[1]]) - viewangle;
-	angle2 = R_PointToAngleEx(viewx, viewy, bspcoord[check[2]], bspcoord[check[3]]) - viewangle;
+	angle1 = R_PointToAngle64(bspcoord[check[0]], bspcoord[check[1]]) - viewangle;
+	angle2 = R_PointToAngle64(bspcoord[check[2]], bspcoord[check[3]]) - viewangle;
 
 	if ((signed)angle1 < (signed)angle2)
 	{
diff --git a/src/r_defs.h b/src/r_defs.h
index dbede806e..3746643c6 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -587,7 +587,7 @@ typedef struct subsector_s
 {
 	sector_t *sector;
 	INT16 numlines;
-	UINT16 firstline;
+	UINT32 firstline;
 	struct polyobj_s *polyList; // haleyjd 02/19/06: list of polyobjects
 	size_t validcount;
 } subsector_t;
diff --git a/src/r_main.c b/src/r_main.c
index cd5e255ed..3763092fc 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -266,13 +266,13 @@ INT32 R_PointOnSide(fixed_t x, fixed_t y, node_t *node)
 	if (!node->dy)
 		return y <= node->y ? node->dx < 0 : node->dx > 0;
 
-	x -= node->x;
-	y -= node->y;
+	fixed_t dx = (x >> 1) - (node->x >> 1);
+	fixed_t dy = (y >> 1) - (node->y >> 1);
 
 	// Try to quickly decide by looking at sign bits.
-	if ((node->dy ^ node->dx ^ x ^ y) < 0)
-		return (node->dy ^ x) < 0;  // (left is negative)
-	return FixedMul(y, node->dx>>FRACBITS) >= FixedMul(node->dy>>FRACBITS, x);
+	if ((node->dy ^ node->dx ^ dx ^ dy) < 0)
+		return (node->dy ^ dx) < 0;  // (left is negative)
+	return FixedMul(dy, node->dx>>FRACBITS) >= FixedMul(node->dy>>FRACBITS, dx);
 }
 
 // killough 5/2/98: reformatted
@@ -289,13 +289,13 @@ INT32 R_PointOnSegSide(fixed_t x, fixed_t y, seg_t *line)
 	if (!ldy)
 		return y <= ly ? ldx < 0 : ldx > 0;
 
-	x -= lx;
-	y -= ly;
+	fixed_t dx = (x >> 1) - (lx >> 1);
+	fixed_t dy = (y >> 1) - (ly >> 1);
 
 	// Try to quickly decide by looking at sign bits.
-	if ((ldy ^ ldx ^ x ^ y) < 0)
-		return (ldy ^ x) < 0;          // (left is negative)
-	return FixedMul(y, ldx>>FRACBITS) >= FixedMul(ldy>>FRACBITS, x);
+	if ((ldy ^ ldx ^ dx ^ dy) < 0)
+		return (ldy ^ dx) < 0;          // (left is negative)
+	return FixedMul(dy, ldx>>FRACBITS) >= FixedMul(ldy>>FRACBITS, dx);
 }
 
 //