- Use tests less prone to overflow on very steep slopes when detecting which side of a plane

the camera is on. Mostly, this means testing the distance of the camera to the plane rather
  than computing the plane's Z at the camera and comparing that with the camera's Z.

SVN r4220 (trunk)

src/p_interaction.cpp

@@ -348,7 +348,7 @@ void AActor::Die (AActor *source, AActor *inflictor, int dmgflags)
 				int realgibhealth = realthis->GibHealth();
 				if (realthis->health >= realgibhealth)
 				{
-					realthis->health = realgibhealth -1; // if morphed was gibbed, so must original be (where allowed)
+					realthis->health = realgibhealth -1; // if morphed was gibbed, so must original be (where allowed)l
 				}
 			}
 			realthis->Die(source, inflictor, dmgflags);

src/r_bsp.cpp

@@ -346,7 +346,7 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec,
 	{
 		sector_t *heightsec = viewsector->heightsec;
 		bool underwater = r_fakingunderwater ||
-			(heightsec && viewz <= heightsec->floorplane.ZatPoint (viewx, viewy));
+			(heightsec && heightsec->floorplane.PointOnSide(viewx, viewy, viewz) <= 0);
 		bool doorunderwater = false;
 		int diffTex = (s->MoreFlags & SECF_CLIPFAKEPLANES);
 
@@ -405,9 +405,7 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec,
 			}
 		}
 
-//		fixed_t refflorz = s->floorplane.ZatPoint (viewx, viewy);
 		fixed_t refceilz = s->ceilingplane.ZatPoint (viewx, viewy);
-//		fixed_t orgflorz = sec->floorplane.ZatPoint (viewx, viewy);
 		fixed_t orgceilz = sec->ceilingplane.ZatPoint (viewx, viewy);
 
 #if 1
@@ -482,7 +480,7 @@ sector_t *R_FakeFlat(sector_t *sec, sector_t *tempsec,
 			}
 			FakeSide = FAKED_BelowFloor;
 		}
-		else if (heightsec && viewz >= heightsec->ceilingplane.ZatPoint (viewx, viewy) &&
+		else if (heightsec && heightsec->ceilingplane.PointOnSide(viewx, viewy, viewz) <= 0 &&
 				 orgceilz > refceilz && !(s->MoreFlags & SECF_FAKEFLOORONLY))
 		{	// Above-ceiling hack
 			tempsec->ceilingplane		= s->ceilingplane;
@@ -1084,7 +1082,7 @@ void R_Subsector (subsector_t *sub)
 		basecolormap = frontsector->ColorMap;
 	}
 
-	ceilingplane = frontsector->ceilingplane.ZatPoint (viewx, viewy) > viewz ||
+	ceilingplane = frontsector->ceilingplane.PointOnSide(viewx, viewy, viewz) > 0 ||
 		frontsector->GetTexture(sector_t::ceiling) == skyflatnum ||
 		(frontsector->CeilingSkyBox != NULL && frontsector->CeilingSkyBox->bAlways) ||
 		(frontsector->heightsec && 
@@ -1123,7 +1121,7 @@ void R_Subsector (subsector_t *sub)
 	// killough 3/7/98: Add (x,y) offsets to flats, add deep water check
 	// killough 3/16/98: add floorlightlevel
 	// killough 10/98: add support for skies transferred from sidedefs
-	floorplane = frontsector->floorplane.ZatPoint (viewx, viewy) < viewz || // killough 3/7/98
+	floorplane = frontsector->floorplane.PointOnSide(viewx, viewy, viewz) > 0 || // killough 3/7/98
 		frontsector->GetTexture(sector_t::floor) == skyflatnum ||
 		(frontsector->FloorSkyBox != NULL && frontsector->FloorSkyBox->bAlways) ||
 		(frontsector->heightsec &&

src/r_defs.h

@@ -212,10 +212,16 @@ struct secplane_t
 
 	fixed_t a, b, c, d, ic;
 
+	// Returns < 0 : behind; == 0 : on; > 0 : in front
+	int PointOnSide (fixed_t x, fixed_t y, fixed_t z) const
+	{
+		return TMulScale16(a,x, b,y, c,z) + d;
+	}
+
 	// Returns the value of z at (0,0) This is used by the 3D floor code which does not handle slopes
 	fixed_t Zat0 () const
 	{
-		return ic < 0? d:-d;
+		return ic < 0 ? d : -d;
 	}
 
 	// Returns the value of z at (x,y)

src/r_plane.cpp

@@ -1697,7 +1697,7 @@ void R_DrawTiltedPlane (visplane_t *pl, fixed_t alpha, bool additive, bool maske
 		plane_sz[0] = -plane_sz[0];
 	}
 
-	planelightfloat = (r_TiltVisibility * lxscale * lyscale) / (float)(abs(pl->height.ZatPoint (viewx, viewy) - viewz));
+	planelightfloat = (r_TiltVisibility * lxscale * lyscale) / (fabs(pl->height.ZatPoint(FIXED2DBL(viewx), FIXED2DBL(viewy)) - FIXED2DBL(viewz))) / 65536.0;
 
 	if (pl->height.c > 0)
 		planelightfloat = -planelightfloat;

src/r_segs.cpp

@@ -2242,10 +2242,10 @@ void R_NewWall (bool needlights)
 	// killough 3/7/98: add deep water check
 	if (frontsector->GetHeightSec() == NULL)
 	{
-		if (frontsector->floorplane.ZatPoint (viewx, viewy) >= viewz)       // above view plane
+		if (frontsector->floorplane.PointOnSide(viewx, viewy, viewz) <= 0)	// above view plane
 			markfloor = false;
-		if (frontsector->ceilingplane.ZatPoint (viewx, viewy) <= viewz &&
-			frontsector->GetTexture(sector_t::ceiling) != skyflatnum)   // below view plane
+		if (frontsector->ceilingplane.PointOnSide(viewx, viewy, viewz) <= 0 &&
+			frontsector->GetTexture(sector_t::ceiling) != skyflatnum)		// below view plane
 			markceiling = false;
 	}
 
@@ -2394,13 +2394,13 @@ void R_StoreWallRange (int start, int stop)
 		ds_p->silhouette = 0;
 
 		if (rw_frontfz1 > rw_backfz1 || rw_frontfz2 > rw_backfz2 ||
-			backsector->floorplane.ZatPoint (viewx, viewy) > viewz)
+			backsector->floorplane.PointOnSide(viewx, viewy, viewz) < 0)
 		{
 			ds_p->silhouette = SIL_BOTTOM;
 		}
 
 		if (rw_frontcz1 < rw_backcz1 || rw_frontcz2 < rw_backcz2 ||
-			backsector->ceilingplane.ZatPoint (viewx, viewy) < viewz)
+			backsector->ceilingplane.PointOnSide(viewx, viewy, viewz) < 0)
 		{
 			ds_p->silhouette |= SIL_TOP;
 		}

src/r_utility.cpp

@@ -849,15 +849,17 @@ void R_SetupFrame (AActor *actor)
 	TArray<lightlist_t> &lightlist = viewsector->e->XFloor.lightlist;
 	if (lightlist.Size() > 0)
 	{
-		for(unsigned int i=0;i<lightlist.Size();i++)
+		for(unsigned int i = 0; i < lightlist.Size(); i++)
 		{
-			fixed_t lightbottom;
-			if (i<lightlist.Size()-1) 
-				lightbottom = lightlist[i+1].plane.ZatPoint(viewx, viewy);
-			else 
-				lightbottom = viewsector->floorplane.ZatPoint(viewx, viewy);
-
-			if (lightbottom < viewz)
+			secplane_t *plane;
+			int viewside;
+			plane = (i < lightlist.Size()-1) ? &lightlist[i+1].plane : &viewsector->floorplane;
+			viewside = plane->PointOnSide(viewx, viewy, viewz);
+			// Reverse the direction of the test if the plane was downward facing.
+			// We want to know if the view is above it, whatever its orientation may be.
+			if (plane->c < 0)
+				viewside = -viewside;
+			if (viewside > 0)
 			{
 				// 3d floor 'fog' is rendered as a blending value
 				PalEntry blendv = lightlist[i].blend;
@@ -874,9 +876,9 @@ void R_SetupFrame (AActor *actor)
 		const sector_t *s = viewsector->GetHeightSec();
 		if (s != NULL)
 		{
-			newblend = viewz < s->floorplane.ZatPoint (viewx, viewy)
+			newblend = s->floorplane.PointOnSide(viewx, viewy, viewz) < 0
 				? s->bottommap
-				: viewz > s->ceilingplane.ZatPoint (viewx, viewy)
+				: s->ceilingplane.PointOnSide(viewx, viewy, viewz) < 0
 				? s->topmap
 				: s->midmap;
 			if (APART(newblend) == 0 && newblend >= numfakecmaps)