diff --git a/src/m_fixed.c b/src/m_fixed.c
index d45bb70bf..412494e3e 100644
--- a/src/m_fixed.c
+++ b/src/m_fixed.c
@@ -121,6 +121,13 @@ fixed_t FixedHypot(fixed_t x, fixed_t y)
 	return FixedMul(ax, yx1); // |x|*((1 + (x/y)^2)^1/2)
 }
 
+fixed_t FixedEuclidean(fixed_t x2, fixed_t y2, fixed_t x1, fixed_t y1)
+{
+	INT64 dx = x2-x1;
+	INT64 dy = y2-y1;
+	return (fixed_t)llrint(sqrt(dx*dx+dy*dy));
+}
+
 vector2_t *FV2_Load(vector2_t *vec, fixed_t x, fixed_t y)
 {
 	vec->x = x;
diff --git a/src/m_fixed.h b/src/m_fixed.h
index 4609913b7..281802fb6 100644
--- a/src/m_fixed.h
+++ b/src/m_fixed.h
@@ -237,6 +237,17 @@ FUNCMATH fixed_t FixedSqrt(fixed_t x);
 */
 FUNCMATH fixed_t FixedHypot(fixed_t x, fixed_t y);
 
+/**	\brief	The FixedEuclidean function
+
+	\param	x	fixed_t number
+	\param	y	fixed_t number
+
+	\return	sqrt(x*x+y*y)
+
+
+*/
+fixed_t FixedEuclidean(fixed_t x2, fixed_t y2, fixed_t x1, fixed_t y1);
+
 /**	\brief	The FixedFloor function
 
 	\param	x	fixed_t number
diff --git a/src/p_setup.c b/src/p_setup.c
index 93eb75583..8e7b205a8 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -380,30 +380,24 @@ static inline void P_LoadVertexes(lumpnum_t lumpnum)
 	Z_Free(data);
 }
 
-
-//
-// Computes the line length in fracunits, the OpenGL render needs this
-//
-
 /** Computes the length of a seg in fracunits.
-  * This is needed for splats.
   *
   * \param seg Seg to compute length for.
   * \return Length in fracunits.
   */
 fixed_t P_SegLength(seg_t *seg)
 {
-	fixed_t dx, dy;
-
-	// make a vector (start at origin)
-	dx = seg->v2->x - seg->v1->x;
-	dy = seg->v2->y - seg->v1->y;
-
-	return FixedHypot(dx, dy);
+	return FixedEuclidean(seg->v2->x,seg->v2->y,seg->v1->x,seg->v1->y);
 }
 
 #ifdef HWRENDER
-static inline float P_SegLengthf(seg_t *seg)
+/** Computes the length of a seg as a float.
+  * This is needed for OpenGL.
+  *
+  * \param seg Seg to compute length for.
+  * \return Length as a float.
+  */
+static inline float P_SegLengthFloat(seg_t *seg)
 {
 	float dx, dy;
 
@@ -439,11 +433,11 @@ static void P_LoadRawSegs(UINT8 *data, size_t i)
 		li->v1 = &vertexes[SHORT(ml->v1)];
 		li->v2 = &vertexes[SHORT(ml->v2)];
 
-#ifdef HWRENDER // not win32 only 19990829 by Kin
-		// used for the hardware render
-		if (rendermode != render_soft && rendermode != render_none)
+		li->length = P_SegLength(li);
+#ifdef HWRENDER
+		if (rendermode == render_opengl)
 		{
-			li->flength = P_SegLengthf(li);
+			li->flength = P_SegLengthFloat(li);
 			//Hurdler: 04/12/2000: for now, only used in hardware mode
 			li->lightmaps = NULL; // list of static lightmap for this seg
 		}
diff --git a/src/r_bsp.c b/src/r_bsp.c
index 355438272..23a65520a 100644
--- a/src/r_bsp.c
+++ b/src/r_bsp.c
@@ -403,17 +403,17 @@ static void R_AddLine(seg_t *line)
 {
 	INT32 x1, x2;
 	angle_t angle1, angle2, span, tspan;
-	static sector_t tempsec; // ceiling/water hack
+	static sector_t tempsec;
+
+	portalline = false;
 
 	if (line->polyseg && !(line->polyseg->flags & POF_RENDERSIDES))
 		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);
 	curline = line;
-	portalline = false;
-
-	// OPTIMIZE: quickly reject orthogonal back sides.
-	angle1 = R_PointToAngle(line->v1->x, line->v1->y);
-	angle2 = R_PointToAngle(line->v2->x, line->v2->y);
 
 	// Clip to view edges.
 	span = angle1 - angle2;
@@ -592,69 +592,35 @@ INT32 checkcoord[12][4] =
 	{2, 1, 3, 0}
 };
 
-static boolean R_CheckBBox(fixed_t *bspcoord)
+static boolean R_CheckBBox(const fixed_t *bspcoord)
 {
-	INT32 boxpos, sx1, sx2;
-	fixed_t px1, py1, px2, py2;
-	angle_t angle1, angle2, span, tspan;
+	angle_t angle1, angle2;
+	INT32 sx1, sx2, boxpos;
+	const INT32* check;
 	cliprange_t *start;
 
 	// Find the corners of the box that define the edges from current viewpoint.
-	if (viewx <= bspcoord[BOXLEFT])
-		boxpos = 0;
-	else if (viewx < bspcoord[BOXRIGHT])
-		boxpos = 1;
-	else
-		boxpos = 2;
-
-	if (viewy >= bspcoord[BOXTOP])
-		boxpos |= 0;
-	else if (viewy > bspcoord[BOXBOTTOM])
-		boxpos |= 1<<2;
-	else
-		boxpos |= 2<<2;
-
-	if (boxpos == 5)
+	if ((boxpos = (viewx <= bspcoord[BOXLEFT] ? 0 : viewx < bspcoord[BOXRIGHT] ? 1 : 2) + (viewy >= bspcoord[BOXTOP] ? 0 : viewy > bspcoord[BOXBOTTOM] ? 4 : 8)) == 5)
 		return true;
 
-	px1 = bspcoord[checkcoord[boxpos][0]];
-	py1 = bspcoord[checkcoord[boxpos][1]];
-	px2 = bspcoord[checkcoord[boxpos][2]];
-	py2 = bspcoord[checkcoord[boxpos][3]];
+	check = checkcoord[boxpos];
 
-	// check clip list for an open space
-	angle1 = R_PointToAngle2(viewx>>1, viewy>>1, px1>>1, py1>>1) - viewangle;
-	angle2 = R_PointToAngle2(viewx>>1, viewy>>1, px2>>1, py2>>1) - viewangle;
+	// 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;
 
-	span = angle1 - angle2;
-
-	// Sitting on a line?
-	if (span >= ANGLE_180)
-		return true;
-
-	tspan = angle1 + clipangle;
-
-	if (tspan > doubleclipangle)
+	if ((signed)angle1 < (signed)angle2)
 	{
-		tspan -= doubleclipangle;
-
-		// Totally off the left edge?
-		if (tspan >= span)
-			return false;
-
-		angle1 = clipangle;
+		if ((angle1 >= ANGLE_180) && (angle1 < ANGLE_270))
+			angle1 = ANGLE_180-1;
+		else
+			angle2 = -ANGLE_180;
 	}
-	tspan = clipangle - angle2;
-	if (tspan > doubleclipangle)
-	{
-		tspan -= doubleclipangle;
 
-		// Totally off the left edge?
-		if (tspan >= span)
-			return false;
-
-		angle2 = -(signed)clipangle;
-	}
+	if ((signed)angle2 >= (signed)clipangle) return false;
+	if ((signed)angle1 <= -(signed)clipangle) return false;
+	if ((signed)angle1 >= (signed)clipangle) angle1 = clipangle;
+	if ((signed)angle2 <= -(signed)clipangle) angle2 = 0-clipangle;
 
 	// Find the first clippost that touches the source post (adjacent pixels are touching).
 	angle1 = (angle1+ANGLE_90)>>ANGLETOFINESHIFT;
@@ -663,9 +629,7 @@ static boolean R_CheckBBox(fixed_t *bspcoord)
 	sx2 = viewangletox[angle2];
 
 	// Does not cross a pixel.
-	if (sx1 == sx2)
-		return false;
-	sx2--;
+	if (sx1 >= sx2) return false;
 
 	start = solidsegs;
 	while (start->last < sx2)
diff --git a/src/r_defs.h b/src/r_defs.h
index b936c7e7d..1cb4e0815 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -573,6 +573,7 @@ typedef struct seg_s
 	sector_t *frontsector;
 	sector_t *backsector;
 
+	fixed_t length;	// precalculated seg length
 #ifdef HWRENDER
 	// new pointers so that AdjustSegs doesn't mess with v1/v2
 	void *pv1; // polyvertex_t
diff --git a/src/r_main.c b/src/r_main.c
index 23eff452c..cd17f642b 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -355,6 +355,29 @@ fixed_t R_PointToDist(fixed_t x, fixed_t y)
 	return R_PointToDist2(viewx, viewy, x, y);
 }
 
+angle_t R_PointToAngleEx(INT32 x2, INT32 y2, INT32 x1, INT32 y1)
+{
+	INT64 dx = x1-x2;
+	INT64 dy = y1-y2;
+	if (dx < INT32_MIN || dx > INT32_MAX || dy < INT32_MIN || dy > INT32_MAX)
+	{
+		x1 = (int)(dx / 2 + x2);
+		y1 = (int)(dy / 2 + y2);
+	}
+	return (y1 -= y2, (x1 -= x2) || y1) ?
+	x1 >= 0 ?
+	y1 >= 0 ?
+		(x1 > y1) ? tantoangle[SlopeDivEx(y1,x1)] :                            // octant 0
+		ANGLE_90-tantoangle[SlopeDivEx(x1,y1)] :                               // octant 1
+		x1 > (y1 = -y1) ? 0-tantoangle[SlopeDivEx(y1,x1)] :                    // octant 8
+		ANGLE_270+tantoangle[SlopeDivEx(x1,y1)] :                              // octant 7
+		y1 >= 0 ? (x1 = -x1) > y1 ? ANGLE_180-tantoangle[SlopeDivEx(y1,x1)] :  // octant 3
+		ANGLE_90 + tantoangle[SlopeDivEx(x1,y1)] :                             // octant 2
+		(x1 = -x1) > (y1 = -y1) ? ANGLE_180+tantoangle[SlopeDivEx(y1,x1)] :    // octant 4
+		ANGLE_270-tantoangle[SlopeDivEx(x1,y1)] :                              // octant 5
+		0;
+}
+
 //
 // R_ScaleFromGlobalAngle
 // Returns the texture mapping scale for the current line (horizontal span)
diff --git a/src/r_main.h b/src/r_main.h
index 81fa13dea..6ae5aa221 100644
--- a/src/r_main.h
+++ b/src/r_main.h
@@ -58,6 +58,7 @@ INT32 R_PointOnSide(fixed_t x, fixed_t y, node_t *node);
 INT32 R_PointOnSegSide(fixed_t x, fixed_t y, seg_t *line);
 angle_t R_PointToAngle(fixed_t x, fixed_t y);
 angle_t R_PointToAngle2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
+angle_t R_PointToAngleEx(INT32 x2, INT32 y2, INT32 x1, INT32 y1);
 fixed_t R_PointToDist(fixed_t x, fixed_t y);
 fixed_t R_PointToDist2(fixed_t px2, fixed_t py2, fixed_t px1, fixed_t py1);
 
diff --git a/src/r_segs.c b/src/r_segs.c
index 2122cba17..66ec71db8 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -1674,6 +1674,23 @@ static void R_RenderSegLoop (void)
 	}
 }
 
+// Uses precalculated seg->length
+static INT64 R_CalcSegDist(seg_t* seg, INT64 x2, INT64 y2)
+{
+	if (!seg->linedef->dy)
+		return abs(y2 - seg->v1->y);
+	else if (!seg->linedef->dx)
+		return abs(x2 - seg->v1->x);
+	else
+	{
+		INT64 dx = (seg->v2->x)-(seg->v1->x);
+		INT64 dy = (seg->v2->y)-(seg->v1->y);
+		INT64 vdx = x2-(seg->v1->x);
+		INT64 vdy = y2-(seg->v1->y);
+		return ((dy*vdx)-(dx*vdy))/(seg->length);
+	}
+}
+
 //
 // R_StoreWallRange
 // A wall segment will be drawn
@@ -1684,6 +1701,7 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 	fixed_t       hyp;
 	fixed_t       sineval;
 	angle_t       distangle, offsetangle;
+	boolean longboi;
 #ifndef ESLOPE
 	fixed_t       vtop;
 #endif
@@ -1729,10 +1747,15 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 		offsetangle = ANGLE_90;
 
 	distangle = ANGLE_90 - offsetangle;
-	hyp = R_PointToDist (curline->v1->x, curline->v1->y);
 	sineval = FINESINE(distangle>>ANGLETOFINESHIFT);
-	rw_distance = FixedMul (hyp, sineval);
 
+	hyp = R_PointToDist(curline->v1->x, curline->v1->y);
+	rw_distance = FixedMul(hyp, sineval);
+	longboi = (hyp >= INT32_MAX);
+
+	// big room fix
+	if (longboi)
+		rw_distance = (fixed_t)R_CalcSegDist(curline,viewx,viewy);
 
 	ds_p->x1 = rw_x = start;
 	ds_p->x2 = stop;
@@ -2589,8 +2612,18 @@ void R_StoreWallRange(INT32 start, INT32 stop)
 		if (offsetangle > ANGLE_90)
 			offsetangle = ANGLE_90;
 
-		sineval = FINESINE(offsetangle >>ANGLETOFINESHIFT);
-		rw_offset = FixedMul (hyp, sineval);
+		sineval = FINESINE(offsetangle>>ANGLETOFINESHIFT);
+		rw_offset = FixedMul(hyp, sineval);
+
+		// big room fix
+		if (longboi)
+		{
+			INT64 dx = (curline->v2->x)-(curline->v1->x);
+			INT64 dy = (curline->v2->y)-(curline->v1->y);
+			INT64 vdx = viewx-(curline->v1->x);
+			INT64 vdy = viewy-(curline->v1->y);
+			rw_offset = ((dx*vdx-dy*vdy))/(curline->length);
+		}
 
 		if (rw_normalangle-rw_angle1 < ANGLE_180)
 			rw_offset = -rw_offset;
diff --git a/src/tables.c b/src/tables.c
index d4e0e5df6..7d5137075 100644
--- a/src/tables.c
+++ b/src/tables.c
@@ -37,6 +37,15 @@ unsigned SlopeDiv(unsigned num, unsigned den)
 	return ans <= SLOPERANGE ? ans : SLOPERANGE;
 }
 
+UINT64 SlopeDivEx(unsigned int num, unsigned int den)
+{
+	UINT64 ans;
+	if (den < 512)
+		return SLOPERANGE;
+	ans = ((UINT64)num<<3)/(den>>8);
+	return ans <= SLOPERANGE ? ans : SLOPERANGE;
+}
+
 fixed_t AngleFixed(angle_t af)
 {
 	angle_t wa = ANGLE_180;
diff --git a/src/tables.h b/src/tables.h
index 1ea49a62f..e82b147df 100644
--- a/src/tables.h
+++ b/src/tables.h
@@ -83,6 +83,8 @@ extern angle_t tantoangle[SLOPERANGE+1];
 
 // Utility function, called by R_PointToAngle.
 FUNCMATH unsigned SlopeDiv(unsigned num, unsigned den);
+// Only called by R_PointToAngleEx
+UINT64 SlopeDivEx(unsigned int num, unsigned int den);
 
 // 360 - angle_t(ANGLE_45) = ANGLE_315
 FUNCMATH FUNCINLINE static ATTRINLINE angle_t InvAngle(angle_t a)