- untested partial refactoring of P_CheckPosition.

(This is just a safety commit before doing some more extensive behind-the-scenes refactoring.)

Notable changes here:

 * use the same logic for determining whether a 3D floor is 'below' or 'above' the actor as all the other functions.
 * removed the broken code which tried to detect whether an actor was touching a steep slope. Better use P_LineOpening to find the correct planes and store the results.
 * improved detection whether the slopes on both sides of a plane are identical, using the same data as for steep slope detection.

src/p_3dfloors.cpp

@@ -776,6 +776,7 @@ void P_LineOpening_XFloors (FLineOpening &open, AActor * thing, const line_t *li
 			int highestfloorterrain = -1;
 			FTextureID lowestceilingpic;
 			sector_t *lowestceilingsec = NULL, *highestfloorsec = NULL;
+			secplane_t *highestfloorplanes[2] = { NULL, NULL };
 			
 			highestfloorpic.SetInvalid();
 			lowestceilingpic.SetInvalid();
@@ -808,6 +809,7 @@ void P_LineOpening_XFloors (FLineOpening &open, AActor * thing, const line_t *li
 						highestfloorpic = *rover->top.texture;
 						highestfloorterrain = rover->model->GetTerrain(rover->top.isceiling);
 						highestfloorsec = j == 0 ? linedef->frontsector : linedef->backsector;
+						highestfloorplanes[j] = rover->top.plane;
 					}
 					if(ff_top > lowestfloor[j] && ff_top <= thing->Z() + thing->MaxStepHeight) lowestfloor[j] = ff_top;
 				}
@@ -826,6 +828,16 @@ void P_LineOpening_XFloors (FLineOpening &open, AActor * thing, const line_t *li
 				open.top = lowestceiling;
 				open.ceilingpic = lowestceilingpic;
 				open.topsec = lowestceilingsec;
+				if (highestfloorplanes[0])
+				{
+					open.frontfloorplane = *highestfloorplanes[0];
+					if (open.frontfloorplane.c < 0) open.frontfloorplane.FlipVert();
+				}
+				if (highestfloorplanes[1])
+				{
+					open.backfloorplane = *highestfloorplanes[1];
+					if (open.backfloorplane.c < 0) open.backfloorplane.FlipVert();
+				}
 			}
 			
 			open.lowfloor = MIN(lowestfloor[0], lowestfloor[1]);

src/p_3dmidtex.cpp

@@ -294,7 +294,9 @@ bool P_LineOpening_3dMidtex(AActor *thing, const line_t *linedef, FLineOpening &
 				open.abovemidtex = true;
 				open.floorpic = linedef->sidedef[0]->GetTexture(side_t::mid);
 				open.floorterrain = TerrainTypes[open.floorpic];
-				
+				open.frontfloorplane.SetAtHeight(tt, sector_t::floor);
+				open.backfloorplane.SetAtHeight(tt, sector_t::floor);
+
 			}
 			// returns true if it touches the midtexture
 			return (abs(thing->Z() - tt) <= thing->MaxStepHeight);

src/p_map.cpp

@@ -276,7 +276,7 @@ static bool PIT_FindFloorCeiling(FMultiBlockLinesIterator &mit, FMultiBlockLines
 
 void P_GetFloorCeilingZ(FCheckPosition &tmf, int flags)
 {
-	sector_t *sec = (!(flags & FFCF_SAMESECTOR) || tmf.thing->Sector == NULL)? P_PointInSector(tmf.x, tmf.y) : tmf.thing->Sector;
+	sector_t *sec = (!(flags & FFCF_SAMESECTOR) || tmf.thing->Sector == NULL)? P_PointInSector(tmf.x, tmf.y) : tmf.sector;
 	F3DFloor *ffc, *fff;
 
 	tmf.ceilingz = sec->NextHighestCeilingAt(tmf.thing, tmf.z + tmf.thing->height, flags, &tmf.ceilingsector, &ffc);
@@ -316,6 +316,10 @@ void P_FindFloorCeiling(AActor *actor, int flags)
 	{
 		flags |= FFCF_3DRESTRICT;
 	}
+	if (flags & FFCF_SAMESECTOR)
+	{
+		tmf.sector = actor->Sector;
+	}
 	P_GetFloorCeilingZ(tmf, flags);
 	assert(tmf.thing->Sector != NULL);
 
@@ -759,8 +763,9 @@ int P_GetMoveFactor(const AActor *mo, int *frictionp)
 //==========================================================================
 
 static // killough 3/26/98: make static
-bool PIT_CheckLine(line_t *ld, const FBoundingBox &box, FCheckPosition &tm)
+bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::CheckResult &cres, const FBoundingBox &box, FCheckPosition &tm)
 {
+	line_t *ld = cres.line;
 	bool rail = false;
 
 	if (box.Right() <= ld->bbox[BOXLEFT]
@@ -802,7 +807,6 @@ bool PIT_CheckLine(line_t *ld, const FBoundingBox &box, FCheckPosition &tm)
 	bool NotBlocked = ((tm.thing->flags3 & MF3_NOBLOCKMONST)
 		|| ((i_compatflags & COMPATF_NOBLOCKFRIENDS) && (tm.thing->flags & MF_FRIENDLY)));
 
-	fixedvec3 pos = tm.thing->PosRelative(ld);
 	if (!(Projectile) || (ld->flags & (ML_BLOCKEVERYTHING | ML_BLOCKPROJECTILE)))
 	{
 		if (ld->flags & ML_RAILING)
@@ -821,55 +825,33 @@ bool PIT_CheckLine(line_t *ld, const FBoundingBox &box, FCheckPosition &tm)
 			}
 			tm.thing->BlockingLine = ld;
 			// Calculate line side based on the actor's original position, not the new one.
-			CheckForPushSpecial(ld, P_PointOnLineSide(pos.x, pos.y, ld), tm.thing, false);
+			CheckForPushSpecial(ld, P_PointOnLineSide(cres.position.x, cres.position.y, ld), tm.thing, false);
 			return false;
 		}
 	}
 
-	// [RH] Steep sectors count as dropoffs (unless already in one)
+	fixedvec2 ref = FindRefPoint(ld, cres.position);
+	FLineOpening open;
+
+	P_LineOpening(open, tm.thing, ld, ref.x, ref.y, cres.position.x, cres.position.y, cres.portalflags);
+
+	// [RH] Steep sectors count as dropoffs, if the actor touches the boundary between a steep slope and something else
 	if (!(tm.thing->flags & MF_DROPOFF) &&
 		!(tm.thing->flags & (MF_NOGRAVITY | MF_NOCLIP)))
 	{
-		secplane_t frontplane, backplane;
 		// Check 3D floors as well
-		frontplane = P_FindFloorPlane(ld->frontsector, pos.x, pos.y, tm.thing->floorz);
-		backplane = P_FindFloorPlane(ld->backsector, pos.x, pos.y, tm.thing->floorz);
-		if (frontplane.c < STEEPSLOPE || backplane.c < STEEPSLOPE)
+		if ((open.frontfloorplane.c < STEEPSLOPE) != (open.backfloorplane.c < STEEPSLOPE))
 		{
-			const msecnode_t *node = tm.thing->touching_sectorlist;
-			bool allow = false;
-			int count = 0;
-			while (node != NULL)
-			{
-				count++;
-				if (node->m_sector->floorplane.c < STEEPSLOPE)
-				{
-					allow = true;
-					break;
-				}
-				node = node->m_tnext;
-			}
-			if (!allow)
-			{
-				return false;
-			}
+			// on the boundary of a steep slope
+			return false;
 		}
 	}
 
-	fixedvec2 rpos = { tm.x, tm.y };
-	fixedvec2 ref = FindRefPoint(ld, rpos);
-	FLineOpening open;
-
-	P_LineOpening(open, tm.thing, ld, ref.x, ref.y, tm.x, tm.y, 0);
-
-	// the floorplane on both sides is identical with the current one
-	// so don't mess around with the z-position.
-	if (ld->frontsector->floorplane == ld->backsector->floorplane &&
-		ld->frontsector->floorplane == tm.thing->Sector->floorplane &&
-		!ld->frontsector->e->XFloor.ffloors.Size() && !ld->backsector->e->XFloor.ffloors.Size() &&
-		!open.abovemidtex)
+	// If the floor planes on both sides we should recalculate open.bottom at the actual position we are checking
+	// This is to avoid bumpy movement when crossing a linedef with the same slope on both sides.
+	if (open.frontfloorplane == open.backfloorplane)
 	{
-		open.bottom = INT_MIN;
+		open.bottom = open.frontfloorplane.ZatPoint(cres.position.x, cres.position.y);
 	}
 
 	if (rail &&
@@ -1017,8 +999,9 @@ static bool CanAttackHurt(AActor *victim, AActor *shooter)
 //
 //==========================================================================
 
-bool PIT_CheckThing(AActor *thing, FCheckPosition &tm)
+bool PIT_CheckThing(FMultiBlockThingsIterator &it, FMultiBlockThingsIterator::CheckResult &cres, const FBoundingBox &box, FCheckPosition &tm)
 {
+	AActor *thing = cres.thing;
 	fixed_t topz;
 	bool 	solid;
 	int 	damage;
@@ -1440,56 +1423,29 @@ bool P_CheckPosition(AActor *thing, fixed_t x, fixed_t y, FCheckPosition &tm, bo
 
 	tm.x = x;
 	tm.y = y;
+	tm.z = thing->Z();
 
-	newsec = P_PointInSector(x, y);
+	newsec = tm.sector = P_PointInSector(x, y);
 	tm.ceilingline = thing->BlockingLine = NULL;
 
-	// The base floor / ceiling is from the subsector that contains the point.
+	// Retrieve the base floor / ceiling from the target location.
 	// Any contacted lines the step closer together will adjust them.
-	tm.floorz = tm.dropoffz = newsec->LowestFloorAt(x, y, &tm.floorsector);
-	tm.ceilingz = newsec->HighestCeilingAt(x, y, &tm.ceilingsector);
-	tm.floorpic = tm.floorsector->GetTexture(sector_t::floor);
-	tm.floorterrain = tm.floorsector->GetTerrain(sector_t::floor);
-	tm.ceilingpic = tm.ceilingsector->GetTexture(sector_t::ceiling);
-	tm.touchmidtex = false;
-	tm.abovemidtex = false;
-
-	//Added by MC: Fill the tmsector.
-	tm.sector = newsec;
-
-	//Check 3D floors
-	if (!thing->IsNoClip2() && newsec->e->XFloor.ffloors.Size())
+	if (!thing->IsNoClip2())
 	{
-		F3DFloor*  rover;
-		fixed_t    delta1;
-		fixed_t    delta2;
-		int        thingtop = thing->Z() + (thing->height == 0 ? 1 : thing->height);
-
-		for (unsigned i = 0; i<newsec->e->XFloor.ffloors.Size(); i++)
-		{
-			rover = newsec->e->XFloor.ffloors[i];
-			if (!(rover->flags & FF_SOLID) || !(rover->flags & FF_EXISTS)) continue;
-
-			fixed_t ff_bottom = rover->bottom.plane->ZatPoint(x, y);
-			fixed_t ff_top = rover->top.plane->ZatPoint(x, y);
-
-			delta1 = thing->Z() - (ff_bottom + ((ff_top - ff_bottom) / 2));
-			delta2 = thingtop - (ff_bottom + ((ff_top - ff_bottom) / 2));
-
-			if (ff_top > tm.floorz && abs(delta1) < abs(delta2))
-			{
-				tm.floorz = tm.dropoffz = ff_top;
-				tm.floorpic = *rover->top.texture;
-				tm.floorterrain = rover->model->GetTerrain(rover->top.isceiling);
-			}
-			if (ff_bottom < tm.ceilingz && abs(delta1) >= abs(delta2))
-			{
-				tm.ceilingz = ff_bottom;
-				tm.ceilingpic = *rover->bottom.texture;
-			}
-		}
+		P_GetFloorCeilingZ(tm, FFCF_SAMESECTOR);
+	}
+	else
+	{
+		// With noclip2, we must ignore 3D floors and go right to the uppermost ceiling and lowermost floor.
+		tm.floorz = tm.dropoffz = newsec->LowestFloorAt(x, y, &tm.floorsector);
+		tm.ceilingz = newsec->HighestCeilingAt(x, y, &tm.ceilingsector);
+		tm.floorpic = tm.floorsector->GetTexture(sector_t::floor);
+		tm.floorterrain = tm.floorsector->GetTerrain(sector_t::floor);
+		tm.ceilingpic = tm.ceilingsector->GetTexture(sector_t::ceiling);
 	}
 
+	tm.touchmidtex = false;
+	tm.abovemidtex = false;
 	validcount++;
 	spechit.Clear();
 
@@ -1507,51 +1463,52 @@ bool P_CheckPosition(AActor *thing, fixed_t x, fixed_t y, FCheckPosition &tm, bo
 	tm.stepthing = NULL;
 	FBoundingBox box(x, y, thing->radius);
 
-	{
-		FBlockThingsIterator it2(box);
-		AActor *th;
-		while ((th = it2.Next()))
-		{
-			if (!PIT_CheckThing(th, tm))
-			{ // [RH] If a thing can be stepped up on, we need to continue checking
-				// other things in the blocks and see if we hit something that is
-				// definitely blocking. Otherwise, we need to check the lines, or we
-				// could end up stuck inside a wall.
-				AActor *BlockingMobj = thing->BlockingMobj;
+	FPortalGroupArray pcheck;
+	FMultiBlockThingsIterator it2(pcheck, x, y, thing->Z(), thing->height, thing->radius);
+	FMultiBlockThingsIterator::CheckResult tcres;
 
-				if (BlockingMobj == NULL || (i_compatflags & COMPATF_NO_PASSMOBJ))
-				{ // Thing slammed into something; don't let it move now.
-					thing->height = realheight;
-					return false;
-				}
-				else if (!BlockingMobj->player && !(thing->flags & (MF_FLOAT | MF_MISSILE | MF_SKULLFLY)) &&
-					BlockingMobj->Top() - thing->Z() <= thing->MaxStepHeight)
-				{
-					if (thingblocker == NULL ||
-						BlockingMobj->Z() > thingblocker->Z())
-					{
-						thingblocker = BlockingMobj;
-					}
-					thing->BlockingMobj = NULL;
-				}
-				else if (thing->player &&
-					thing->Top() - BlockingMobj->Z() <= thing->MaxStepHeight)
-				{
-					if (thingblocker)
-					{ // There is something to step up on. Return this thing as
-						// the blocker so that we don't step up.
-						thing->height = realheight;
-						return false;
-					}
-					// Nothing is blocking us, but this actor potentially could
-					// if there is something else to step on.
-					thing->BlockingMobj = NULL;
-				}
-				else
-				{ // Definitely blocking
+	while ((it2.Next(&tcres)))
+	{
+		if (!PIT_CheckThing(it2, tcres, it2.Box(), tm))
+		{ // [RH] If a thing can be stepped up on, we need to continue checking
+			// other things in the blocks and see if we hit something that is
+			// definitely blocking. Otherwise, we need to check the lines, or we
+			// could end up stuck inside a wall.
+			AActor *BlockingMobj = thing->BlockingMobj;
+
+			// If this blocks through a line portal with a vertical displacement, it will always completely block. There is no way to step up onto such an actor.
+			if (BlockingMobj == NULL || (i_compatflags & COMPATF_NO_PASSMOBJ) || tcres.zdiff != 0)
+			{ // Thing slammed into something; don't let it move now.
+				thing->height = realheight;
+				return false;
+			}
+			else if (!BlockingMobj->player && !(thing->flags & (MF_FLOAT | MF_MISSILE | MF_SKULLFLY)) &&
+				BlockingMobj->Top() - thing->Z() <= thing->MaxStepHeight)
+			{
+				if (thingblocker == NULL ||
+					BlockingMobj->Z() > thingblocker->Z())
+				{
+					thingblocker = BlockingMobj;
+				}
+				thing->BlockingMobj = NULL;
+			}
+			else if (thing->player &&
+				thing->Top() - BlockingMobj->Z() <= thing->MaxStepHeight)
+			{
+				if (thingblocker)
+				{ // There is something to step up on. Return this thing as
+					// the blocker so that we don't step up.
 					thing->height = realheight;
 					return false;
 				}
+				// Nothing is blocking us, but this actor potentially could
+				// if there is something else to step on.
+				thing->BlockingMobj = NULL;
+			}
+			else
+			{ // Definitely blocking
+				thing->height = realheight;
+				return false;
 			}
 		}
 	}
@@ -1574,7 +1531,8 @@ bool P_CheckPosition(AActor *thing, fixed_t x, fixed_t y, FCheckPosition &tm, bo
 	if (actorsonly || (thing->flags & MF_NOCLIP))
 		return (thing->BlockingMobj = thingblocker) == NULL;
 
-	FBlockLinesIterator it(box);
+	FMultiBlockLinesIterator it(pcheck, thing);
+	FMultiBlockLinesIterator::CheckResult lcres;
 	line_t *ld;
 
 	fixed_t thingdropoffz = tm.floorz;
@@ -1583,9 +1541,9 @@ bool P_CheckPosition(AActor *thing, fixed_t x, fixed_t y, FCheckPosition &tm, bo
 
 	bool good = true;
 
-	while ((ld = it.Next()))
+	while (it.Next(&lcres))
 	{
-		good &= PIT_CheckLine(ld, box, tm);
+		good &= PIT_CheckLine(it, lcres, it.Box(), tm);
 	}
 	if (!good)
 	{

src/p_maputl.cpp

@@ -229,6 +229,8 @@ void P_LineOpening (FLineOpening &open, AActor *actor, const line_t *linedef,
 			open.floorterrain = back->GetTerrain(sector_t::floor);
 			open.lowfloor = ff;
 		}
+		open.frontfloorplane = front->floorplane;
+		open.backfloorplane = back->floorplane;
 	}
 	else
 	{ // Dummy stuff to have some sort of opening for the 3D checks to modify
@@ -240,6 +242,8 @@ void P_LineOpening (FLineOpening &open, AActor *actor, const line_t *linedef,
 		open.floorterrain = -1;
 		open.bottom = FIXED_MIN;
 		open.lowfloor = FIXED_MAX;
+		open.frontfloorplane.SetAtHeight(FIXED_MIN, sector_t::floor);
+		open.backfloorplane.SetAtHeight(FIXED_MIN, sector_t::floor);
 	}
 
 	// Check 3D floors
@@ -798,6 +802,7 @@ bool FMultiBlockLinesIterator::Next(FMultiBlockLinesIterator::CheckResult *item)
 		item->position.x = offset.x;
 		item->position.y = offset.y;
 		item->position.z = checkpoint.z;
+		item->zdiff = 0;
 		item->portalflags = portalflags;
 		return true;
 	}
@@ -1085,6 +1090,7 @@ bool FMultiBlockThingsIterator::Next(FMultiBlockThingsIterator::CheckResult *ite
 	{
 		item->thing = thing;
 		item->position = checkpoint + Displacements(basegroup, thing->Sector->PortalGroup);
+		item->zdiff = 0;
 		item->portalflags = portalflags;
 		return true;
 	}

src/p_maputl.h

@@ -99,6 +99,8 @@ struct FLineOpening
 	sector_t		*topsec;
 	FTextureID		ceilingpic;
 	FTextureID		floorpic;
+	secplane_t		frontfloorplane;
+	secplane_t		backfloorplane;
 	int				floorterrain;
 	bool			touchmidtex;
 	bool			abovemidtex;
@@ -221,6 +223,7 @@ public:
 	{
 		line_t *line;
 		fixedvec3 position;
+		fixed_t zdiff;
 		int portalflags;
 	};
 
@@ -306,6 +309,7 @@ public:
 	{
 		AActor *thing;
 		fixedvec3 position;
+		fixed_t zdiff;
 		int portalflags;
 	};
 

src/r_defs.h

@@ -345,6 +345,21 @@ struct secplane_t
 		return -TMulScale16 (a, v->x, b, v->y, z, c);
 	}
 
+	void SetAtHeight(fixed_t height, int ceiling)
+	{
+		a = b = 0;
+		if (ceiling)
+		{
+			c = ic = -FRACUNIT;
+			d = height;
+		}
+		else
+		{
+			c = ic = FRACUNIT;
+			d = -height;
+		}
+	}
+
 	bool CopyPlaneIfValid (secplane_t *dest, const secplane_t *opp) const;
 
 };