diff --git a/source/build/src/clip.cpp b/source/build/src/clip.cpp
index bd46d90f1..fdc6763b7 100644
--- a/source/build/src/clip.cpp
+++ b/source/build/src/clip.cpp
@@ -59,6 +59,15 @@ static inline void get_floorspr_points(DCoreActor *spr, int32_t px, int32_t py,
 
 }
 
+inline int32_t spriteGetZOfSlope(const spritetypebase* tspr, int dax, int day, int heinum)
+{
+	if (heinum == 0) return tspr->int_pos().Z;
+
+	int const j = DMulScale(bsin(tspr->int_ang() + 1024), day - tspr->int_pos().Y, -bsin(tspr->int_ang() + 512), dax - tspr->int_pos().X, 4);
+	return tspr->int_pos().Z + MulScale(heinum, j, 18);
+}
+
+
 //
 // clipinsideboxline
 //
diff --git a/source/core/gamefuncs.h b/source/core/gamefuncs.h
index 90dea7d03..9a6482472 100644
--- a/source/core/gamefuncs.h
+++ b/source/core/gamefuncs.h
@@ -461,12 +461,12 @@ inline int tspriteGetSlope(const tspritetype* spr)
 	return !(spr->clipdist & TSPR_SLOPESPRITE) ? 0 : uint8_t(spr->xoffset) + (int8_t(spr->yoffset) << 8);
 }
 
-inline int32_t spriteGetZOfSlope(const spritetypebase* tspr, int dax, int day, int heinum)
+inline double spriteGetZOfSlopef(const spritetypebase* tspr, const DVector2& pos, int heinum)
 {
-	if (heinum == 0) return tspr->int_pos().Z;
-
-	int const j = DMulScale(bsin(tspr->int_ang() + 1024), day - tspr->int_pos().Y, -bsin(tspr->int_ang() + 512), dax - tspr->int_pos().X, 4);
-	return tspr->int_pos().Z + MulScale(heinum, j, 18);
+	if (heinum == 0) return tspr->pos.Z;
+	auto ang = tspr->angle;
+	double factor =  -ang.Sin() * (pos.X - tspr->pos.Y) - ang.Cos() * (pos.X - tspr->pos.X);
+	return tspr->pos.Z + heinum * factor * (1./4096.);
 }
 
 inline int inside(int x, int y, const sectortype* sect)
diff --git a/source/core/rendering/scene/hw_drawinfo.cpp b/source/core/rendering/scene/hw_drawinfo.cpp
index bbd284c6e..c3c91faaf 100644
--- a/source/core/rendering/scene/hw_drawinfo.cpp
+++ b/source/core/rendering/scene/hw_drawinfo.cpp
@@ -146,7 +146,6 @@ void HWDrawInfo::StartScene(FRenderViewpoint& parentvp, HWViewpointUniforms* uni
 		VPUniforms.mClipLine.X = -10000000.0f;
 		VPUniforms.mShadowmapFilter = gl_shadowmap_filter;
 	}
-	vec2_t view = { int(Viewpoint.Pos.X * 16), int(Viewpoint.Pos.Y * -16) };
 
 	ClearBuffers();
 
diff --git a/source/core/rendering/scene/hw_flats.cpp b/source/core/rendering/scene/hw_flats.cpp
index 37e39a5ea..f2d78561d 100644
--- a/source/core/rendering/scene/hw_flats.cpp
+++ b/source/core/rendering/scene/hw_flats.cpp
@@ -133,18 +133,16 @@ void HWFlat::MakeVertices(HWDrawInfo* di)
 		float y = !(Sprite->cstat & CSTAT_SPRITE_YFLIP) ? 0.f : 1.f;
 		if (Sprite->clipdist & TSPR_SLOPESPRITE)
 		{
-			int posx = int(di->Viewpoint.Pos.X * 16.f);
-			int posy = int(di->Viewpoint.Pos.Y * -16.f);
-			int posz = int(di->Viewpoint.Pos.Z * -256.f);
+			DVector3 posi = { di->Viewpoint.Pos.X, -di->Viewpoint.Pos.Y, -di->Viewpoint.Pos.Z };
 
 			// Make adjustments for poorly aligned slope sprites on floors or ceilings
 			constexpr float ONPLANE_THRESHOLD = 3.f;
-			if (spriteGetZOfSlope(Sprite, posx, posy, tspriteGetSlope(Sprite)) < posz)
+			if (spriteGetZOfSlopef(Sprite, posi.XY(), tspriteGetSlope(Sprite)) < posi.Z)
 			{
 				float maxofs = -FLT_MAX, minofs = FLT_MAX;
 				for (int i = 0; i < 4; i++)
 				{
-					float vz = -getceilzofslopeptrf(Sprite->sectp, pos[i].X, pos[i].Y);
+					float vz = -getceilzofslopeptrf(Sprite->sectp, posi);
 					float sz = z - ofsz[i];
 					int diff = vz - sz;
 					if (diff > maxofs) maxofs = diff;
@@ -157,7 +155,7 @@ void HWFlat::MakeVertices(HWDrawInfo* di)
 				float maxofs = -FLT_MAX, minofs = FLT_MAX;
 				for (int i = 0; i < 4; i++)
 				{
-					float vz = -getflorzofslopeptrf(Sprite->sectp, pos[i].X, pos[i].Y);
+					float vz = -getflorzofslopeptrf(Sprite->sectp, posi);
 					float sz = z - ofsz[i];
 					int diff = vz - sz;
 					if (diff > maxofs) maxofs = diff;
@@ -435,8 +433,9 @@ void HWFlat::ProcessFlatSprite(HWDrawInfo* di, tspritetype* sprite, sectortype*
 	// Weird Build logic that really makes no sense.
 	if ((sprite->cstat & CSTAT_SPRITE_ONE_SIDE) != 0)
 	{
-		double myz = !(sprite->clipdist & TSPR_SLOPESPRITE) ? z :
-			spriteGetZOfSlope(sprite, int(di->Viewpoint.Pos.X * 16), int(di->Viewpoint.Pos.Y * -16), tspriteGetSlope(sprite)) * -(1. / 256.);
+		DVector2 pos = { di->Viewpoint.Pos.X, -di->Viewpoint.Pos.Y };
+
+		double myz = !(sprite->clipdist & TSPR_SLOPESPRITE) ? z : -spriteGetZOfSlopef(sprite, pos, tspriteGetSlope(sprite));
 		if ((di->Viewpoint.Pos.Z < myz) == ((sprite->cstat & CSTAT_SPRITE_YFLIP) == 0))
 			return;
 	}
diff --git a/source/core/rendering/scene/hw_portal.h b/source/core/rendering/scene/hw_portal.h
index 16aff022d..d0899d6b5 100644
--- a/source/core/rendering/scene/hw_portal.h
+++ b/source/core/rendering/scene/hw_portal.h
@@ -231,14 +231,7 @@ public:
 struct HWLinePortal : public HWScenePortalBase
 {
 protected:
-	// this must be the same as at the start of line_t, so that we can pass in this structure directly to P_ClipLineToPortal.
 	walltype* line;
-	/*
-	vec2_t	*v1, *v2;	// vertices, from v1 to v2
-	DVector2	delta;		// precalculated v2 - v1 for side checking
-
-	angle_t		angv1, angv2;	// for quick comparisons with a line or subsector
-	*/
 
 	HWLinePortal(FPortalSceneState *state, walltype *line) : HWScenePortalBase(state)
 	{