Merge branch 'linkdraw_reliability' into 'master'

MF2_LINKDRAW reliability improvements

Seriously improves the reliability of the linkdraw system (in Software, the only rendering engine which actually does anything with this information), reducing the number of visual errors it produces significantly. Deliberately engineered to only affect objects with MF2_LINKDRAW applied.

Of particular note: Standing in shallow pools of water as Smiles will now reliably associate the bottom half of the tails following mobj with the underwater portion of Smiles' body, and the flicking ends with his un-submerged head.

Test with ```<root>/!LatestSRB2Files/srb2win_branch_linkdraw.exe``` and ```<root>/toaster/smiles.wad```.

See merge request !101

src/r_things.c

@@ -817,7 +817,7 @@ static void R_DrawVisSprite(vissprite_t *vis)
 
 	colfunc = basecolfunc; // hack: this isn't resetting properly somewhere.
 	dc_colormap = vis->colormap;
-	if ((vis->mobj->flags & MF_BOSS) && (vis->mobj->flags2 & MF2_FRET) && (leveltime & 1)) // Bosses "flash"
+	if (!(vis->cut & SC_PRECIP) && (vis->mobj->flags & MF_BOSS) && (vis->mobj->flags2 & MF2_FRET) && (leveltime & 1)) // Bosses "flash"
 	{
 		// translate certain pixels to white
 		colfunc = transcolfunc;
@@ -832,7 +832,7 @@ static void R_DrawVisSprite(vissprite_t *vis)
 	{
 		colfunc = transtransfunc;
 		dc_transmap = vis->transmap;
-		if (vis->mobj->skin && vis->mobj->sprite == SPR_PLAY) // MT_GHOST LOOKS LIKE A PLAYER SO USE THE PLAYER TRANSLATION TABLES. >_>
+		if (!(vis->cut & SC_PRECIP) && vis->mobj->skin && vis->mobj->sprite == SPR_PLAY) // MT_GHOST LOOKS LIKE A PLAYER SO USE THE PLAYER TRANSLATION TABLES. >_>
 		{
 			size_t skinnum = (skin_t*)vis->mobj->skin-skins;
 			dc_translation = R_GetTranslationColormap((INT32)skinnum, vis->mobj->color, GTC_CACHE);
@@ -851,7 +851,7 @@ static void R_DrawVisSprite(vissprite_t *vis)
 		colfunc = transcolfunc;
 
 		// New colormap stuff for skins Tails 06-07-2002
-		if (vis->mobj->skin && vis->mobj->sprite == SPR_PLAY) // This thing is a player!
+		if (!(vis->cut & SC_PRECIP) && vis->mobj->skin && vis->mobj->sprite == SPR_PLAY) // This thing is a player!
 		{
 			size_t skinnum = (skin_t*)vis->mobj->skin-skins;
 			dc_translation = R_GetTranslationColormap((INT32)skinnum, vis->mobj->color, GTC_CACHE);
@@ -881,18 +881,18 @@ static void R_DrawVisSprite(vissprite_t *vis)
 	frac = vis->startfrac;
 	windowtop = windowbottom = sprbotscreen = INT32_MAX;
 
-	if (vis->mobj->skin && ((skin_t *)vis->mobj->skin)->flags & SF_HIRES)
+	if (!(vis->cut & SC_PRECIP) && vis->mobj->skin && ((skin_t *)vis->mobj->skin)->flags & SF_HIRES)
 		this_scale = FixedMul(this_scale, ((skin_t *)vis->mobj->skin)->highresscale);
 	if (this_scale <= 0)
 		this_scale = 1;
 	if (this_scale != FRACUNIT)
 	{
-		if (!vis->isScaled)
+		if (!(vis->cut & SC_ISSCALED))
 		{
 			vis->scale = FixedMul(vis->scale, this_scale);
 			vis->scalestep = FixedMul(vis->scalestep, this_scale);
 			vis->xiscale = FixedDiv(vis->xiscale,this_scale);
-			vis->isScaled = true;
+			vis->cut |= SC_ISSCALED;
 		}
 		dc_texturemid = FixedDiv(dc_texturemid,this_scale);
 	}
@@ -934,7 +934,7 @@ static void R_DrawVisSprite(vissprite_t *vis)
 			sprtopscreen = (centeryfrac - FixedMul(dc_texturemid, spryscale));
 			dc_iscale = (0xffffffffu / (unsigned)spryscale);
 		}
-		if (vis->vflip)
+		if (vis->cut & SC_VFLIP)
 			R_DrawFlippedMaskedColumn(column, patch->height);
 		else
 			R_DrawMaskedColumn(column);
@@ -1013,7 +1013,7 @@ static void R_DrawPrecipitationVisSprite(vissprite_t *vis)
 //
 // R_SplitSprite
 // runs through a sector's lightlist and
-static void R_SplitSprite(vissprite_t *sprite, mobj_t *thing)
+static void R_SplitSprite(vissprite_t *sprite)
 {
 	INT32 i, lightnum, lindex;
 	INT16 cutfrac;
@@ -1049,6 +1049,8 @@ static void R_SplitSprite(vissprite_t *sprite, mobj_t *thing)
 		// adjust the heights.
 		newsprite = M_Memcpy(R_NewVisSprite(), sprite, sizeof (vissprite_t));
 
+		newsprite->cut |= (sprite->cut & SC_FLAGMASK);
+
 		sprite->cut |= SC_BOTTOM;
 		sprite->gz = testheight;
 
@@ -1081,15 +1083,7 @@ static void R_SplitSprite(vissprite_t *sprite, mobj_t *thing)
 
 			newsprite->extra_colormap = sector->lightlist[i].extra_colormap;
 
-/*
+			if (!((newsprite->cut & SC_FULLBRIGHT) && (!newsprite->extra_colormap || !newsprite->extra_colormap->fog)))
-			if (thing->frame & FF_TRANSMASK)
-				;
-			else if (thing->flags2 & MF2_SHADOW)
-				;
-			else
-*/
-			if (!((thing->frame & (FF_FULLBRIGHT|FF_TRANSMASK) || thing->flags2 & MF2_SHADOW)
-				&& (!newsprite->extra_colormap || !newsprite->extra_colormap->fog)))
 			{
 				lindex = FixedMul(sprite->xscale, FixedDiv(640, vid.width))>>(LIGHTSCALESHIFT);
 
@@ -1109,6 +1103,7 @@ static void R_SplitSprite(vissprite_t *sprite, mobj_t *thing)
 //
 static void R_ProjectSprite(mobj_t *thing)
 {
+	mobj_t *oldthing = thing;
 	fixed_t tr_x, tr_y;
 	fixed_t gxt, gyt;
 	fixed_t tx, tz;
@@ -1128,6 +1123,8 @@ static void R_ProjectSprite(mobj_t *thing)
 
 	vissprite_t *vis;
 
+	spritecut_e cut = SC_NONE;
+
 	angle_t ang = 0; // compiler complaints
 	fixed_t iscale;
 	fixed_t scalestep;
@@ -1326,24 +1323,14 @@ static void R_ProjectSprite(mobj_t *thing)
 	if ((thing->flags2 & MF2_LINKDRAW) && thing->tracer) // toast 16/09/16 (SYMMETRY)
 	{
 		fixed_t linkscale;
-#if 0 // support for chains of linkdraw - probably not network safe to modify mobjs during rendering
-		mobj_t *link, *link2;
 
-		for (link = thing->tracer; (link->tracer && (link->flags2 & MF2_LINKDRAW)); link = link->tracer)
+		thing = thing->tracer;
-			link->flags2 &= ~MF2_LINKDRAW; // to prevent infinite loops, otherwise would just be a ;
 
-		for (link2 = thing->tracer; (link2->tracer && (link2 != link)); link2 = link2->tracer)
+		if (thing->sprite == SPR_NULL || thing->flags2 & MF2_DONTDRAW)
-			link->flags2 |= MF2_LINKDRAW; // only needed for correction of the above
+			return;
 
-		if (link->flags2 & MF2_LINKDRAW)
+		tr_x = thing->x - viewx;
-			link->flags2 &= ~MF2_LINKDRAW; // let's try and make sure this doesn't happen again...
+		tr_y = thing->y - viewy;
-
-		tr_x = link->x - viewx;
-		tr_y = link->y - viewy;
-#else
-		tr_x = thing->tracer->x - viewx;
-		tr_y = thing->tracer->y - viewy;
-#endif
 		gxt = FixedMul(tr_x, viewcos);
 		gyt = -FixedMul(tr_y, viewsin);
 		tz = gxt-gyt;
@@ -1356,6 +1343,7 @@ static void R_ProjectSprite(mobj_t *thing)
 			dispoffset *= -1; // if it's physically behind, make sure it's ordered behind (if dispoffset > 0)
 
 		sortscale = linkscale; // now make sure it's linked
+		cut = SC_LINKDRAW;
 	}
 
 	// PORTAL SPRITE CLIPPING
@@ -1374,12 +1362,12 @@ static void R_ProjectSprite(mobj_t *thing)
 		// When vertical flipped, draw sprites from the top down, at least as far as offsets are concerned.
 		// sprite height - sprite topoffset is the proper inverse of the vertical offset, of course.
 		// remember gz and gzt should be seperated by sprite height, not thing height - thing height can be shorter than the sprite itself sometimes!
-		gz = thing->z + thing->height - FixedMul(spritecachedinfo[lump].topoffset, this_scale);
+		gz = oldthing->z + oldthing->height - FixedMul(spritecachedinfo[lump].topoffset, this_scale);
 		gzt = gz + FixedMul(spritecachedinfo[lump].height, this_scale);
 	}
 	else
 	{
-		gzt = thing->z + FixedMul(spritecachedinfo[lump].topoffset, this_scale);
+		gzt = oldthing->z + FixedMul(spritecachedinfo[lump].topoffset, this_scale);
 		gz = gzt - FixedMul(spritecachedinfo[lump].height, this_scale);
 	}
 
@@ -1469,7 +1457,7 @@ static void R_ProjectSprite(mobj_t *thing)
 	vis->sector = thing->subsector->sector;
 	vis->szt = (INT16)((centeryfrac - FixedMul(vis->gzt - viewz, sortscale))>>FRACBITS);
 	vis->sz = (INT16)((centeryfrac - FixedMul(vis->gz - viewz, sortscale))>>FRACBITS);
-	vis->cut = SC_NONE;
+	vis->cut = cut;
 	if (thing->subsector->sector->numlights)
 		vis->extra_colormap = thing->subsector->sector->lightlist[light].extra_colormap;
 	else
@@ -1506,12 +1494,15 @@ static void R_ProjectSprite(mobj_t *thing)
 	// specific translucency
 	if (!cv_translucency.value)
 		; // no translucency
-	else if (thing->flags2 & MF2_SHADOW) // actually only the player should use this (temporary invisibility)
+	else if (oldthing->flags2 & MF2_SHADOW) // actually only the player should use this (temporary invisibility)
 		vis->transmap = transtables + ((tr_trans80-1)<<FF_TRANSSHIFT); // because now the translucency is set through FF_TRANSMASK
-	else if (thing->frame & FF_TRANSMASK)
+	else if (oldthing->frame & FF_TRANSMASK)
-		vis->transmap = transtables + (thing->frame & FF_TRANSMASK) - 0x10000;
+		vis->transmap = transtables + (oldthing->frame & FF_TRANSMASK) - 0x10000;
 
-	if (((thing->frame & FF_FULLBRIGHT) || (thing->flags2 & MF2_SHADOW))
+	if ((oldthing->frame & FF_FULLBRIGHT) || (oldthing->flags2 & MF2_SHADOW))
+		vis->cut |= SC_FULLBRIGHT;
+
+	if (vis->cut & SC_FULLBRIGHT
 		&& (!vis->extra_colormap || !vis->extra_colormap->fog))
 	{
 		// full bright: goggles
@@ -1528,14 +1519,11 @@ static void R_ProjectSprite(mobj_t *thing)
 		vis->colormap = spritelights[lindex];
 	}
 
-	vis->precip = false;
+	if (vflip)
-
+		vis->cut |= SC_VFLIP;
-	vis->vflip = vflip;
-
-	vis->isScaled = false;
 
 	if (thing->subsector->sector->numlights)
-		R_SplitSprite(vis, thing);
+		R_SplitSprite(vis);
 
 	// Debug
 	++objectsdrawn;
@@ -1559,7 +1547,7 @@ static void R_ProjectPrecipitationSprite(precipmobj_t *thing)
 	fixed_t iscale;
 
 	//SoM: 3/17/2000
-	fixed_t gz ,gzt;
+	fixed_t gz, gzt;
 
 	// transform the origin point
 	tr_x = thing->x - viewx;
@@ -1695,16 +1683,14 @@ static void R_ProjectPrecipitationSprite(precipmobj_t *thing)
 	else
 		vis->transmap = NULL;
 
+	vis->mobj = (mobj_t *)thing;
 	vis->mobjflags = 0;
-	vis->cut = SC_NONE;
+	vis->cut = SC_PRECIP;
 	vis->extra_colormap = thing->subsector->sector->extra_colormap;
 	vis->heightsec = thing->subsector->sector->heightsec;
 
 	// Fullbright
 	vis->colormap = colormaps;
-	vis->precip = true;
-	vis->vflip = false;
-	vis->isScaled = false;
 }
 
 // R_AddSprites
@@ -1797,7 +1783,7 @@ static vissprite_t vsprsortedhead;
 
 void R_SortVisSprites(void)
 {
-	UINT32       i;
+	UINT32       i, linkedvissprites = 0;
 	vissprite_t *ds, *dsprev, *dsnext, *dsfirst;
 	vissprite_t *best = NULL;
 	vissprite_t  unsorted;
@@ -1821,22 +1807,91 @@ void R_SortVisSprites(void)
 
 		ds->next = dsnext;
 		ds->prev = dsprev;
+		ds->linkdraw = NULL;
 	}
 
 	// Fix first and last. ds still points to the last one after the loop
 	dsfirst->prev = &unsorted;
 	unsorted.next = dsfirst;
 	if (ds)
+	{
 		ds->next = &unsorted;
+		ds->linkdraw = NULL;
+	}
 	unsorted.prev = ds;
 
+	// bundle linkdraw
+	for (ds = unsorted.prev; ds != &unsorted; ds = ds->prev)
+	{
+		if (!(ds->cut & SC_LINKDRAW))
+			continue;
+
+		// reuse dsfirst...
+		for (dsfirst = unsorted.prev; dsfirst != &unsorted; dsfirst = dsfirst->prev)
+		{
+			// don't connect if it's also a link
+			if (dsfirst->cut & SC_LINKDRAW)
+				continue;
+
+			// don't connect if it's not the tracer
+			if (dsfirst->mobj != ds->mobj)
+				continue;
+
+			// don't connect if the tracer's top is cut off, but lower than the link's top
+			if ((dsfirst->cut & SC_TOP)
+			&& dsfirst->szt > ds->szt)
+				continue;
+
+			// don't connect if the tracer's bottom is cut off, but higher than the link's bottom
+			if ((dsfirst->cut & SC_BOTTOM)
+			&& dsfirst->sz < ds->sz)
+				continue;
+
+			break;
+		}
+
+		// remove from chain
+		ds->next->prev = ds->prev;
+		ds->prev->next = ds->next;
+		linkedvissprites++;
+
+		if (dsfirst != &unsorted)
+		{
+			if (!(ds->cut & SC_FULLBRIGHT))
+				ds->colormap = dsfirst->colormap;
+			ds->extra_colormap = dsfirst->extra_colormap;
+
+			// reusing dsnext...
+			dsnext = dsfirst->linkdraw;
+
+			if (!dsnext || ds->dispoffset < dsnext->dispoffset)
+			{
+				ds->next = dsnext;
+				dsfirst->linkdraw = ds;
+			}
+			else
+			{
+				for (; dsnext->next != NULL; dsnext = dsnext->next)
+					if (ds->dispoffset < dsnext->next->dispoffset)
+						break;
+				ds->next = dsnext->next;
+				dsnext->next = ds;
+			}
+		}
+	}
+
 	// pull the vissprites out by scale
 	vsprsortedhead.next = vsprsortedhead.prev = &vsprsortedhead;
-	for (i = 0; i < visspritecount; i++)
+	for (i = 0; i < visspritecount-linkedvissprites; i++)
 	{
 		bestscale = bestdispoffset = INT32_MAX;
 		for (ds = unsorted.next; ds != &unsorted; ds = ds->next)
 		{
+#ifdef PARANOIA
+			if (ds->cut & SC_LINKDRAW)
+				I_Error("R_SortVisSprites: no link or discardal made for linkdraw!");
+#endif
+
 			if (ds->sortscale < bestscale)
 			{
 				bestscale = ds->sortscale;
@@ -2090,20 +2145,6 @@ static void R_CreateDrawNodes(void)
 			}
 			else if (r2->seg)
 			{
-#if 0 //#ifdef POLYOBJECTS_PLANES
-				if (r2->seg->curline->polyseg && rover->mobj && P_MobjInsidePolyobj(r2->seg->curline->polyseg, rover->mobj)) {
-					// Determine if we need to sort in front of the polyobj, based on the planes. This fixes the issue where
-					// polyobject planes render above the object standing on them. (A bit hacky... but it works.) -Red
-					mobj_t *mo = rover->mobj;
-					sector_t *po = r2->seg->curline->backsector;
-
-					if (po->ceilingheight < viewz && mo->z+mo->height > po->ceilingheight)
-						continue;
-
-					if (po->floorheight > viewz && mo->z < po->floorheight)
-						continue;
-				}
-#endif
 				if (rover->x1 > r2->seg->x2 || rover->x2 < r2->seg->x1)
 					continue;
 
@@ -2230,7 +2271,7 @@ static void R_DrawPrecipitationSprite(vissprite_t *spr)
 void R_ClipSprites(void)
 {
 	vissprite_t *spr;
-	for (;clippedvissprites < visspritecount; clippedvissprites++)
+	for (; clippedvissprites < visspritecount; clippedvissprites++)
 	{
 		drawseg_t *ds;
 		INT32		x;
@@ -2451,10 +2492,24 @@ void R_DrawMasked(void)
 			next = r2->prev;
 
 			// Tails 08-18-2002
-			if (r2->sprite->precip == true)
+			if (r2->sprite->cut & SC_PRECIP)
 				R_DrawPrecipitationSprite(r2->sprite);
-			else
+			else if (!r2->sprite->linkdraw)
 				R_DrawSprite(r2->sprite);
+			else // unbundle linkdraw
+			{
+				vissprite_t *ds = r2->sprite->linkdraw;
+
+				for (;
+				(ds != NULL && r2->sprite->dispoffset > ds->dispoffset);
+				ds = ds->next)
+					R_DrawSprite(ds);
+
+				R_DrawSprite(r2->sprite);
+
+				for (; ds != NULL; ds = ds->next)
+					R_DrawSprite(ds);
+			}
 
 			R_DoneWithNode(r2);
 			r2 = next;

src/r_things.h

@@ -127,9 +127,19 @@ typedef struct
 // -----------
 typedef enum
 {
+	// actual cuts
 	SC_NONE = 0,
 	SC_TOP = 1,
-	SC_BOTTOM = 2
+	SC_BOTTOM = 1<<1,
+	// other flags
+	SC_PRECIP = 1<<2,
+	SC_LINKDRAW = 1<<3,
+	SC_FULLBRIGHT = 1<<4,
+	SC_VFLIP = 1<<5,
+	SC_ISSCALED = 1>>6,
+	// masks
+	SC_CUTMASK = SC_TOP|SC_BOTTOM,
+	SC_FLAGMASK = ~SC_CUTMASK
 } spritecut_e;
 
 // A vissprite_t is a thing that will be drawn during a refresh,
@@ -140,6 +150,9 @@ typedef struct vissprite_s
 	struct vissprite_s *prev;
 	struct vissprite_s *next;
 
+	// Bonus linkdraw pointer.
+	struct vissprite_s *linkdraw;
+
 	mobj_t *mobj; // for easy access
 
 	INT32 x1, x2;
@@ -178,9 +191,6 @@ typedef struct vissprite_s
 
 	INT16 clipbot[MAXVIDWIDTH], cliptop[MAXVIDWIDTH];
 
-	boolean precip;
-	boolean vflip; // Flip vertically
-	boolean isScaled;
 	INT32 dispoffset; // copy of info->dispoffset, affects ordering but not drawing
 } vissprite_t;