diff --git a/src/edata.cpp b/src/edata.cpp
index 8176e6a98..da41400a8 100644
--- a/src/edata.cpp
+++ b/src/edata.cpp
@@ -140,10 +140,10 @@ struct EDSector
 	bool colorSet;
 
 	// colormaptop//bottom cannot be used because ZDoom has no corresponding properties.
-
-	FTransform planexform[2];
+	double xoffs[2], yoffs[2];
+	DAngle angle[2];
 	DWORD portalflags[2];
-	fixed_t overlayalpha[2];
+	double Overlayalpha[2];
 };
 
 static FString EDMap;
@@ -275,7 +275,7 @@ static void parseSector(FScanner &sc)
 	EDSector sec;
 
 	memset(&sec, 0, sizeof(sec));
-	sec.overlayalpha[sector_t::floor] = sec.overlayalpha[sector_t::ceiling] = OPAQUE;
+	sec.Overlayalpha[sector_t::floor] = sec.Overlayalpha[sector_t::ceiling] = 1.;
 	sec.floorterrain = sec.ceilingterrain = -1;
 
 	sc.MustGetStringName("{");
@@ -398,19 +398,19 @@ static void parseSector(FScanner &sc)
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::floor].angle = FLOAT2ANGLE(sc.Float);
+			sec.angle[sector_t::floor] = sc.Float;
 		}
 		else if (sc.Compare("flooroffsetx"))
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::floor].xoffs = FLOAT2FIXED(sc.Float);
+			sec.xoffs[sector_t::floor] = sc.Float;
 		}
 		else if (sc.Compare("flooroffsety"))
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::floor].yoffs = FLOAT2FIXED(sc.Float);
+			sec.yoffs[sector_t::floor] = sc.Float;
 		}
 		else if (sc.Compare("ceilingterrain"))
 		{
@@ -422,19 +422,19 @@ static void parseSector(FScanner &sc)
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::ceiling].angle = FLOAT2ANGLE(sc.Float);
+			sec.angle[sector_t::ceiling] = sc.Float;
 		}
 		else if (sc.Compare("ceilingoffsetx"))
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::ceiling].xoffs = FLOAT2FIXED(sc.Float);
+			sec.xoffs[sector_t::ceiling] = sc.Float;
 		}
 		else if (sc.Compare("ceilingoffsety"))
 		{
 			sc.CheckString("=");
 			sc.MustGetFloat();
-			sec.planexform[sector_t::ceiling].yoffs = FLOAT2FIXED(sc.Float);
+			sec.yoffs[sector_t::ceiling] = sc.Float;
 		}
 		else if (sc.Compare("colormaptop") || sc.Compare("colormapbottom"))
 		{
@@ -464,14 +464,14 @@ static void parseSector(FScanner &sc)
 				sc.MustGetNumber();
 				if (sc.CheckString("%")) sc.Float = sc.Number / 100.f;
 				else sc.Float = sc.Number / 255.f;
-				sec.overlayalpha[sector_t::floor] = FLOAT2FIXED(sc.Float);
+				sec.Overlayalpha[sector_t::floor] = sc.Float;
 			}
 			else if (sc.Compare("ceiling"))
 			{
 				sc.MustGetFloat();
 				if (sc.CheckString("%")) sc.Float = sc.Number / 100.f;
 				else sc.Float = sc.Number / 255.f;
-				sec.overlayalpha[sector_t::floor] = FLOAT2FIXED(sc.Float);
+				sec.Overlayalpha[sector_t::floor] = sc.Float;
 			}
 		}
 		else if (sc.Compare("portalflags"))
@@ -742,10 +742,10 @@ void ProcessEDSector(sector_t *sec, int recordnum)
 	const DWORD pflagmask = PLANEF_DISABLED | PLANEF_NORENDER | PLANEF_NOPASS | PLANEF_BLOCKSOUND | PLANEF_ADDITIVE;
 	for (int i = 0; i < 2; i++)
 	{
-		sec->planes[i].xform.xoffs = esec->planexform[i].xoffs;
-		sec->planes[i].xform.yoffs = esec->planexform[i].yoffs;
-		sec->planes[i].xform.angle = esec->planexform[i].angle;
-		sec->planes[i].alpha = esec->overlayalpha[i];
+		sec->SetXOffset(i, esec->xoffs[i]);
+		sec->SetYOffset(i, esec->yoffs[i]);
+		sec->SetAngle(i, esec->angle[i]);
+		sec->SetAlpha(i, esec->Overlayalpha[i]);
 		sec->planes[i].Flags = (sec->planes[i].Flags & ~pflagmask) | esec->portalflags[i];
 	}
 }
diff --git a/src/m_bbox.cpp b/src/m_bbox.cpp
index 6baba2a56..be6721209 100644
--- a/src/m_bbox.cpp
+++ b/src/m_bbox.cpp
@@ -76,27 +76,27 @@ int FBoundingBox::BoxOnLineSide (const line_t *ld) const
 	int p1;
 	int p2;
 		
-	if (ld->dx == 0)
+	if (ld->Delta().X == 0)
 	{ // ST_VERTICAL
 		p1 = m_Box[BOXRIGHT] < ld->v1->fixX();
 		p2 = m_Box[BOXLEFT] < ld->v1->fixX();
-		if (ld->dy < 0)
+		if (ld->Delta().Y < 0)
 		{
 			p1 ^= 1;
 			p2 ^= 1;
 		}
 	}
-	else if (ld->dy == 0)
+	else if (ld->Delta().Y == 0)
 	{ // ST_HORIZONTAL:
 		p1 = m_Box[BOXTOP] > ld->v1->fixY();
 		p2 = m_Box[BOXBOTTOM] > ld->v1->fixY();
-		if (ld->dx < 0)
+		if (ld->Delta().X < 0)
 		{
 			p1 ^= 1;
 			p2 ^= 1;
 		}
 	}
-	else if ((ld->dy ^ ld->dx) >= 0)
+	else if ((ld->Delta().X * ld->Delta().Y) >= 0)
 	{ // ST_POSITIVE:
 		p1 = P_PointOnLineSide (m_Box[BOXLEFT], m_Box[BOXTOP], ld);
 		p2 = P_PointOnLineSide (m_Box[BOXRIGHT], m_Box[BOXBOTTOM], ld);
diff --git a/src/p_3dfloors.cpp b/src/p_3dfloors.cpp
index ffdb7cec7..a029f7ad9 100644
--- a/src/p_3dfloors.cpp
+++ b/src/p_3dfloors.cpp
@@ -135,14 +135,12 @@ static void P_Add3DFloor(sector_t* sec, sector_t* sec2, line_t* master, int flag
 	{
 		ffloor->bottom.plane = &sec2->floorplane;
 		ffloor->bottom.texture = &sec2->planes[sector_t::floor].Texture;
-		ffloor->bottom.texheight = &sec2->planes[sector_t::floor].TexZ;
 		ffloor->bottom.isceiling = sector_t::floor;
 	}
 	else 
 	{
 		ffloor->bottom.plane = &sec2->ceilingplane;
 		ffloor->bottom.texture = &sec2->planes[sector_t::ceiling].Texture;
-		ffloor->bottom.texheight = &sec2->planes[sector_t::ceiling].TexZ;
 		ffloor->bottom.isceiling = sector_t::ceiling;
 	}
 	
@@ -150,7 +148,6 @@ static void P_Add3DFloor(sector_t* sec, sector_t* sec2, line_t* master, int flag
 	{
 		ffloor->top.plane = &sec2->ceilingplane;
 		ffloor->top.texture = &sec2->planes[sector_t::ceiling].Texture;
-		ffloor->top.texheight = &sec2->planes[sector_t::ceiling].TexZ;
 		ffloor->toplightlevel = &sec2->lightlevel;
 		ffloor->top.isceiling = sector_t::ceiling;
 	}
@@ -158,7 +155,6 @@ static void P_Add3DFloor(sector_t* sec, sector_t* sec2, line_t* master, int flag
 	{
 		ffloor->top.plane = &sec->floorplane;
 		ffloor->top.texture = &sec2->planes[sector_t::floor].Texture;
-		ffloor->top.texheight = &sec2->planes[sector_t::floor].TexZ;
 		ffloor->toplightlevel = &sec->lightlevel;
 		ffloor->top.isceiling = sector_t::floor;
 		ffloor->top.model = sec;
diff --git a/src/p_3dfloors.h b/src/p_3dfloors.h
index 02e25f882..5268da0e2 100644
--- a/src/p_3dfloors.h
+++ b/src/p_3dfloors.h
@@ -68,7 +68,6 @@ struct F3DFloor
 	{
 		secplane_t *	plane;
 		const FTextureID *	texture;
-		const fixed_t *		texheight;
 		sector_t *		model;
 		int				isceiling;
 		int				vindex;
diff --git a/src/p_glnodes.cpp b/src/p_glnodes.cpp
index cc80296da..e4993a273 100644
--- a/src/p_glnodes.cpp
+++ b/src/p_glnodes.cpp
@@ -129,10 +129,10 @@ struct gl5_mapnode_t
 
 static int CheckForMissingSegs()
 {
-	float *added_seglen = new float[numsides];
+	double *added_seglen = new double[numsides];
 	int missing = 0;
 
-	memset(added_seglen, 0, sizeof(float)*numsides);
+	memset(added_seglen, 0, sizeof(double)*numsides);
 	for(int i=0;i<numsegs;i++)
 	{
 		seg_t * seg = &segs[i];
@@ -140,20 +140,15 @@ static int CheckForMissingSegs()
 		if (seg->sidedef!=NULL)
 		{
 			// check all the segs and calculate the length they occupy on their sidedef
-			DVector2 vec1(seg->v2->fixX() - seg->v1->fixX(), seg->v2->fixY() - seg->v1->fixY());
-			added_seglen[seg->sidedef - sides] += float(vec1.Length());
+			DVector2 vec1(seg->v2->fX() - seg->v1->fX(), seg->v2->fY() - seg->v1->fY());
+			added_seglen[seg->sidedef - sides] += vec1.Length();
 		}
 	}
 
 	for(int i=0;i<numsides;i++)
 	{
-		side_t * side =&sides[i];
-		line_t * line = side->linedef;
-
-		DVector2 lvec(line->dx, line->dy);
-		float linelen = float(lvec.Length());
-
-		missing += (added_seglen[i] < linelen - FRACUNIT);
+		double linelen = sides[i].linedef->Delta().Length();
+		missing += (added_seglen[i] < linelen - 1.);
 	}
 
 	delete [] added_seglen;
diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index 2e6004a89..39953bf66 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -410,38 +410,37 @@ bool AActor::FixMapthingPos()
 				continue;
 
 			// Get the exact distance to the line
-			fdivline_t dll, dlv;
-			fixed_t linelen = (fixed_t)g_sqrt((double)ldef->dx*ldef->dx + (double)ldef->dy*ldef->dy);
+			divline_t dll, dlv;
+			double linelen = ldef->Delta().Length();
 
 			P_MakeDivline(ldef, &dll);
 
-			dlv.x = _f_X();
-			dlv.y = _f_Y();
-			dlv.dx = FixedDiv(dll.dy, linelen);
-			dlv.dy = -FixedDiv(dll.dx, linelen);
+			dlv.x = X();
+			dlv.y = Y();
+			dlv.dx = dll.dy / linelen;
+			dlv.dy = -dll.dx / linelen;
 
-			fixed_t distance = abs(P_InterceptVector(&dlv, &dll));
+			double distance = fabs(P_InterceptVector(&dlv, &dll));
 
-			if (distance < _f_radius())
+			if (distance < radius)
 			{
-				DPrintf("%s at (%d,%d) lies on %s line %td, distance = %f\n",
-					this->GetClass()->TypeName.GetChars(), _f_X() >> FRACBITS, _f_Y() >> FRACBITS,
-					ldef->dx == 0 ? "vertical" : ldef->dy == 0 ? "horizontal" : "diagonal",
+				DPrintf("%s at (%f,%f) lies on %s line %td, distance = %f\n",
+					this->GetClass()->TypeName.GetChars(), X(), Y(),
+					ldef->Delta().X == 0 ? "vertical" : ldef->Delta().Y == 0 ? "horizontal" : "diagonal",
 					ldef - lines, FIXED2DBL(distance));
-				angle_t finean = R_PointToAngle2(0, 0, ldef->dx, ldef->dy);
+				DAngle ang = ldef->Delta().Angle();
 				if (ldef->backsector != NULL && ldef->backsector == secstart)
 				{
-					finean += ANGLE_90;
+					ang += 90.;
 				}
 				else
 				{
-					finean -= ANGLE_90;
+					ang -= 90.;
 				}
-				finean >>= ANGLETOFINESHIFT;
 
 				// Get the distance we have to move the object away from the wall
-				distance = _f_radius() - distance;
-				SetXY(_f_X() + FixedMul(distance, finecosine[finean]), _f_Y() + FixedMul(distance, finesine[finean]));
+				distance = radius - distance;
+				SetXY(Pos().XY() + ang.ToVector(distance));
 				ClearInterpolation();
 				success = true;
 			}
@@ -1936,27 +1935,32 @@ int P_VanillaPointOnLineSide(fixed_t x, fixed_t y, const line_t* line)
 	fixed_t	dy;
 	fixed_t	left;
 	fixed_t	right;
+	DVector2 delta = line->Delta();
 
-	if (!line->dx)
+	if (delta.X == 0)
 	{
 		if (x <= line->v1->fixX())
-			return line->dy > 0;
+			return delta.Y > 0;
 
-		return line->dy < 0;
+		return delta.Y < 0;
 	}
-	if (!line->dy)
+	if (delta.Y == 0)
 	{
 		if (y <= line->v1->fixY())
-			return line->dx < 0;
+			return delta.X < 0;
 
-		return line->dx > 0;
+		return delta.X > 0;
 	}
 
+	// Note: This cannot really be converted to floating point 
+	// without breaking the intended use of this function
+	// (i.e. to emulate the horrible imprecision of the entire methpd)
+
 	dx = (x - line->v1->fixX());
 	dy = (y - line->v1->fixY());
 
-	left = FixedMul ( line->dy>>FRACBITS , dx );
-	right = FixedMul ( dy , line->dx>>FRACBITS );
+	left = FixedMul ( int(delta.Y * 256) , dx );
+	right = FixedMul ( dy , int(delta.X * 256) );
 
 	if (right < left)
 		return 0;		// front side
diff --git a/src/p_maputl.h b/src/p_maputl.h
index 56e5a7615..2a68898c1 100644
--- a/src/p_maputl.h
+++ b/src/p_maputl.h
@@ -53,12 +53,12 @@ inline int P_PointOnLineSide (fixed_t x, fixed_t y, const line_t *line)
 
 	return i_compatflags2 & COMPATF2_POINTONLINE
 		? P_VanillaPointOnLineSide(x, y, line)
-		: DMulScale32 (y-line->v1->fixY(), line->dx, line->v1->fixX()-x, line->dy) > 0;
+		: DMulScale32 (y-line->v1->fixY(), line->fixDx(), line->v1->fixX()-x, line->fixDy()) > 0;
 }
 
 inline int P_PointOnLineSidePrecise (fixed_t x, fixed_t y, const line_t *line)
 {
-	return DMulScale32 (y-line->v1->fixY(), line->dx, line->v1->fixX()-x, line->dy) > 0;
+	return DMulScale32 (y-line->v1->fixY(), line->fixDx(), line->v1->fixX()-x, line->fixDy()) > 0;
 }
 
 inline int P_PointOnLineSide(double x, double y, const line_t *line)
@@ -125,8 +125,8 @@ inline void P_MakeDivline (const line_t *li, fdivline_t *dl)
 {
 	dl->x = li->v1->fixX();
 	dl->y = li->v1->fixY();
-	dl->dx = li->dx;
-	dl->dy = li->dy;
+	dl->dx = li->fixDx();
+	dl->dy = li->fixDy();
 }
 
 inline void P_MakeDivline(const line_t *li, divline_t *dl)
diff --git a/src/p_sectors.cpp b/src/p_sectors.cpp
index 678828657..4533fb138 100644
--- a/src/p_sectors.cpp
+++ b/src/p_sectors.cpp
@@ -877,7 +877,7 @@ void sector_t::CheckPortalPlane(int plane)
 	AActor *portal = SkyBoxes[plane];
 	if (!portal || portal->special1 != SKYBOX_LINKEDPORTAL) return;
 
-	double planeh = FIXED2DBL(planes[plane].TexZ);
+	double planeh = GetPlaneTexZF(plane);
 	int obstructed = PLANEF_OBSTRUCTED * (plane == sector_t::floor ?
 		planeh > portal->specialf1 : planeh < portal->specialf1);
 	planes[plane].Flags = (planes[plane].Flags  & ~PLANEF_OBSTRUCTED) | obstructed;
@@ -1225,21 +1225,22 @@ int side_t::GetLightLevel (bool foggy, int baselight, bool is3dlight, int *pfake
 	{
 		if (!(Flags & WALLF_NOFAKECONTRAST) && r_fakecontrast != 0)
 		{
+			DVector2 delta = linedef->Delta();
 			int rel;
 			if (((level.flags2 & LEVEL2_SMOOTHLIGHTING) || (Flags & WALLF_SMOOTHLIGHTING) || r_fakecontrast == 2) &&
-				linedef->dx != 0)
+				delta.X != 0)
 			{
 				rel = xs_RoundToInt // OMG LEE KILLOUGH LIVES! :/
 					(
 						level.WallHorizLight
-						+ fabs(atan(double(linedef->dy) / linedef->dx) / 1.57079)
+						+ fabs(atan(delta.Y / delta.X) / 1.57079)
 						* (level.WallVertLight - level.WallHorizLight)
 					);
 			}
 			else
 			{
-				rel = linedef->dx == 0 ? level.WallVertLight : 
-					  linedef->dy == 0 ? level.WallHorizLight : 0;
+				rel = delta.X == 0 ? level.WallVertLight : 
+					  delta.Y == 0 ? level.WallHorizLight : 0;
 			}
 			if (pfakecontrast != NULL)
 			{
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index a2f4468ff..e751957d3 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -1903,8 +1903,7 @@ void P_AdjustLine (line_t *ld)
 	v1 = ld->v1;
 	v2 = ld->v2;
 
-	ld->dx = v2->fixX() - v1->fixX();
-	ld->dy = v2->fixY() - v1->fixY();
+	ld->setDelta(v2->fX() - v1->fX(), v2->fY() - v1->fY());
 	
 	if (v1->fixX() < v2->fixX())
 	{
@@ -2423,15 +2422,15 @@ static void P_LoopSidedefs (bool firstloop)
 			if (sidetemp[right].b.next != NO_SIDE)
 			{
 				int bestright = right;	// Shut up, GCC
-				angle_t bestang = ANGLE_MAX;
+				DAngle bestang = 360.;
 				line_t *leftline, *rightline;
-				angle_t ang1, ang2, ang;
+				DAngle ang1, ang2, ang;
 
 				leftline = sides[i].linedef;
-				ang1 = R_PointToAngle2 (0, 0, leftline->dx, leftline->dy);
+				ang1 = leftline->Delta().Angle();
 				if (!sidetemp[i].b.lineside)
 				{
-					ang1 += ANGLE_180;
+					ang1 += 180;
 				}
 
 				while (right != NO_SIDE)
@@ -2441,13 +2440,13 @@ static void P_LoopSidedefs (bool firstloop)
 						rightline = sides[right].linedef;
 						if (rightline->frontsector != rightline->backsector)
 						{
-							ang2 = R_PointToAngle2 (0, 0, rightline->dx, rightline->dy);
+							ang2 = rightline->Delta().Angle();
 							if (sidetemp[right].b.lineside)
 							{
-								ang2 += ANGLE_180;
+								ang2 += 180;
 							}
 
-							ang = ang2 - ang1;
+							ang = (ang2 - ang1).Normalized360();
 
 							if (ang != 0 && ang <= bestang)
 							{
diff --git a/src/p_slopes.cpp b/src/p_slopes.cpp
index 1da018281..49c9c5a35 100644
--- a/src/p_slopes.cpp
+++ b/src/p_slopes.cpp
@@ -79,14 +79,14 @@ static void P_SlopeLineToPoint (int lineid, fixed_t x, fixed_t y, fixed_t z, boo
 
 		DVector3 p, v1, v2, cross;
 
-		p[0] = FIXED2DBL (line->v1->fixX());
-		p[1] = FIXED2DBL (line->v1->fixY());
-		p[2] = FIXED2DBL (plane->ZatPoint (line->v1->fixX(), line->v1->fixY()));
-		v1[0] = FIXED2DBL (line->dx);
-		v1[1] = FIXED2DBL (line->dy);
-		v1[2] = FIXED2DBL (plane->ZatPoint (line->v2->fixX(), line->v2->fixY())) - p[2];
-		v2[0] = FIXED2DBL (x - line->v1->fixX());
-		v2[1] = FIXED2DBL (y - line->v1->fixY());
+		p[0] = line->v1->fX();
+		p[1] = line->v1->fY();
+		p[2] = plane->ZatPointF (line->v1);
+		v1[0] = line->Delta().X;
+		v1[1] = line->Delta().Y;
+		v1[2] = plane->ZatPointF (line->v2) - p[2];
+		v2[0] = FIXED2DBL (x) - p[0];
+		v2[1] = FIXED2DBL (y) - p[1];
 		v2[2] = FIXED2DBL (z) - p[2];
 
 		cross = v1 ^ v2;
@@ -487,8 +487,8 @@ static void P_AlignPlane (sector_t *sec, line_t *line, int which)
 			vert = (*probe++)->v2;
 		else
 			vert = (*probe)->v1;
-		dist = fabs((double(line->v1->fixY()) - vert->fixY()) * line->dx -
-					(double(line->v1->fixX()) - vert->fixX()) * line->dy);
+		dist = fabs((double(line->v1->fixY()) - vert->fixY()) * line->fixDx() -
+					(double(line->v1->fixX()) - vert->fixX()) * line->fixDy());
 
 		if (dist > bestdist)
 		{
@@ -508,14 +508,14 @@ static void P_AlignPlane (sector_t *sec, line_t *line, int which)
 	srcheight = (which == 0) ? sec->GetPlaneTexZ(sector_t::floor) : sec->GetPlaneTexZ(sector_t::ceiling);
 	destheight = (which == 0) ? refsec->GetPlaneTexZ(sector_t::floor) : refsec->GetPlaneTexZ(sector_t::ceiling);
 
-	p[0] = FIXED2DBL (line->v1->fixX());
-	p[1] = FIXED2DBL(line->v1->fixY());
+	p[0] = line->v1->fX();
+	p[1] = line->v1->fY();
 	p[2] = FIXED2DBL(destheight);
-	v1[0] = FIXED2DBL(line->dx);
-	v1[1] = FIXED2DBL(line->dy);
+	v1[0] = line->Delta().X;
+	v1[1] = line->Delta().Y;
 	v1[2] = 0;
-	v2[0] = FIXED2DBL(refvert->fixX() - line->v1->fixX());
-	v2[1] = FIXED2DBL(refvert->fixY() - line->v1->fixY());
+	v2[0] = refvert->fX() - line->v1->fX();
+	v2[1] = refvert->fY() - line->v1->fY();
 	v2[2] = FIXED2DBL(srcheight - destheight);
 
 	cross = (v1 ^ v2).Unit();
diff --git a/src/po_man.cpp b/src/po_man.cpp
index 7fbef05f2..5d397c724 100644
--- a/src/po_man.cpp
+++ b/src/po_man.cpp
@@ -943,8 +943,9 @@ void FPolyObj::UpdateBBox ()
 		}
 
 		// Update the line's slopetype
-		line->dx = line->v2->fixX() - line->v1->fixX();
-		line->dy = line->v2->fixY() - line->v1->fixY();
+		line->setDelta(
+			line->v2->fixX() - line->v1->fixX(),
+			line->v2->fixY() - line->v1->fixY());
 	}
 	CalcCenter();
 }
diff --git a/src/portal.cpp b/src/portal.cpp
index 3b31284f1..a4d46c5f0 100644
--- a/src/portal.cpp
+++ b/src/portal.cpp
@@ -251,10 +251,10 @@ static void SetRotation(FLinePortal *port)
 	{
 	line_t *dst = port->mDestination;
 	line_t *line = port->mOrigin;
-	double angle = g_atan2(dst->dy, dst->dx) - g_atan2(line->dy, line->dx) + M_PI;
-	port->mSinRot = FLOAT2FIXED(g_sin(angle));
-	port->mCosRot = FLOAT2FIXED(g_cos(angle));
-	port->mAngleDiff = ToDegrees(angle);
+	DAngle angle = dst->Delta().Angle() - line->Delta().Angle() + 180.;
+	port->mSinRot = FLOAT2FIXED(angle.Sin());
+	port->mCosRot = FLOAT2FIXED(angle.Cos());
+	port->mAngleDiff = angle;
 	}
 }
 
@@ -513,7 +513,7 @@ inline int P_PointOnLineSideExplicit (fixed_t x, fixed_t y, fixed_t x1, fixed_t
 
 inline int P_GetLineSide(fixed_t x, fixed_t y, const line_t *line)
 {
-	return DMulScale32(y - line->v1->fixY(), line->dx, line->v1->fixX() - x, line->dy);
+	return DMulScale32(y - line->v1->fixY(), line->fixDx(), line->v1->fixX() - x, line->fixDy());
 }
 
 bool P_ClipLineToPortal(line_t* line, line_t* portal, fixed_t viewx, fixed_t viewy, bool partial, bool samebehind)
@@ -652,7 +652,7 @@ void P_TranslatePortalZ(line_t* src, fixed_t& z)
 
 fixed_t P_PointLineDistance(line_t* line, fixed_t x, fixed_t y)
 {
-	angle_t angle = R_PointToAngle2(0, 0, line->dx, line->dy);
+	angle_t angle = R_PointToAngle2(0, 0, line->fixDx(), line->fixDy());
 	angle += ANGLE_180;
 
 	fixed_t dx = line->v1->fixX() - x;
diff --git a/src/r_defs.h b/src/r_defs.h
index 84a938747..95b4ce92c 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -449,6 +449,11 @@ public:
 		return FixedMul (ic, -d - DMulScale16 (a, v->fixX(), b, v->fixY()));
 	}
 
+	double ZatPointF(const vertex_t *v) const
+	{
+		return FIXED2DBL(FixedMul(ic, -d - DMulScale16(a, v->fixX(), b, v->fixY())));
+	}
+
 	fixed_t ZatPoint (const AActor *ac) const
 	{
 		return FixedMul (ic, -d - DMulScale16 (a, ac->_f_X(), b, ac->_f_Y()));
@@ -772,6 +777,11 @@ struct sector_t
 		planes[pos].xform.xoffs = o;
 	}
 
+	void SetXOffset(int pos, double o)
+	{
+		planes[pos].xform.xoffs = FLOAT2FIXED(o);
+	}
+
 	void AddXOffset(int pos, fixed_t o)
 	{
 		planes[pos].xform.xoffs += o;
@@ -797,6 +807,11 @@ struct sector_t
 		planes[pos].xform.yoffs = o;
 	}
 
+	void SetYOffset(int pos, double o)
+	{
+		planes[pos].xform.yoffs = FLOAT2FIXED(o);
+	}
+
 	void AddYOffset(int pos, fixed_t o)
 	{
 		planes[pos].xform.yoffs += o;
@@ -866,6 +881,11 @@ struct sector_t
 		planes[pos].xform.angle = o;
 	}
 
+	void SetAngle(int pos, DAngle o)
+	{
+		planes[pos].xform.angle = o.BAMs();
+	}
+
 	angle_t GetAngle(int pos, bool addbase = true) const
 	{
 		if (!addbase)
@@ -976,12 +996,22 @@ struct sector_t
 		if (dirtify) SetAllVerticesDirty();
 	}
 
+	void SetPlaneTexZ(int pos, double val)
+	{
+		planes[pos].TexZ = FLOAT2FIXED(val);
+	}
+
 	void ChangePlaneTexZ(int pos, fixed_t val)
 	{
 		planes[pos].TexZ += val;
 		SetAllVerticesDirty();
 	}
 
+	void ChangePlaneTexZ(int pos, double val)
+	{
+		planes[pos].TexZ += FLOAT2FIXED(val);
+	}
+
 	static inline short ClampLight(int level)
 	{
 		return (short)clamp(level, SHRT_MIN, SHRT_MAX);
@@ -1423,7 +1453,9 @@ FArchive &operator<< (FArchive &arc, side_t::part &p);
 struct line_t
 {
 	vertex_t	*v1, *v2;	// vertices, from v1 to v2
+private:
 	fixed_t 	dx, dy;		// precalculated v2 - v1 for side checking
+public:
 	DWORD		flags;
 	DWORD		activation;	// activation type
 	int			special;
@@ -1452,6 +1484,28 @@ struct line_t
 		return{ FIXED2DBL(dx), FIXED2DBL(dy) };
 	}
 
+	fixed_t fixDx() const
+	{
+		return dx;
+	}
+
+	fixed_t fixDy() const
+	{
+		return dy;
+	}
+
+	void setDelta(fixed_t x, fixed_t y)
+	{
+		dx = x;
+		dy = y;
+	}
+
+	void setDelta(double x, double y)
+	{
+		dx = FLOAT2FIXED(x);
+		dy = FLOAT2FIXED(y);
+	}
+
 	FLinePortal *getPortal() const
 	{
 		return portalindex >= linePortals.Size() ? (FLinePortal*)NULL : &linePortals[portalindex];
diff --git a/src/r_main.cpp b/src/r_main.cpp
index 56945f406..599eb738e 100644
--- a/src/r_main.cpp
+++ b/src/r_main.cpp
@@ -702,11 +702,11 @@ void R_EnterPortal (PortalDrawseg* pds, int depth)
 		vertex_t *v1 = pds->src->v1;
 
 		// Reflect the current view behind the mirror.
-		if (pds->src->dx == 0)
+		if (pds->src->Delta().X == 0)
 		{ // vertical mirror
 			viewx = v1->fixX() - startx + v1->fixX();
 		}
-		else if (pds->src->dy == 0)
+		else if (pds->src->Delta().Y == 0)
 		{ // horizontal mirror
 			viewy = v1->fixY() - starty + v1->fixY();
 		}