Improved weapon interpolation (#2123)

* Improved weapon interpolation

This approach, similar to that of mobj interpolation, eliminates some issues from the old approach, namely interpolation having to be reset upon sprite changes and view-size changes.

* rfomin's patch: remove `pspr_interp`

Co-Authored-By: Roman Fomin <[email protected]>

* Assign `s#2` to `olds#2` when loading savegames

* Assign to `olds#2` properly

---------

Co-authored-by: Roman Fomin <[email protected]>

Author: MrAlaux

src/am_map.c

@@ -2312,10 +2312,7 @@ void AM_Drawer (void)
   }
 
   if (automapoverlay == AM_OVERLAY_OFF)
-  {
     AM_clearFB(mapcolor_back);       //jff 1/5/98 background default color
-    pspr_interp = false;
-  }
   // [Alaux] Dark automap overlay
   else if (automapoverlay == AM_OVERLAY_DARK && !MN_MenuIsShaded())
     V_ShadeScreen();

src/p_mobj.c

@@ -1127,8 +1127,6 @@ void P_SpawnPlayer (mapthing_t* mthing)
 
   p->momx = p->momy = 0;   // killough 10/98: initialize bobbing to 0.
 
-  pspr_interp = false;
-
   // setup gun psprite
 
   P_SetupPsprites (p);

src/p_pspr.c

@@ -167,9 +167,12 @@ static void P_BringUpWeapon(player_t *player)
 
   player->pendingweapon = wp_nochange;
 
+  pspdef_t *psp = &player->psprites[ps_weapon];
+
   // killough 12/98: prevent pistol from starting visibly at bottom of screen:
-  player->psprites[ps_weapon].sy = demo_version >= DV_MBF ? 
-    WEAPONBOTTOM+FRACUNIT*2 : WEAPONBOTTOM;
+  psp->sy = demo_version >= DV_MBF ? WEAPONBOTTOM + FRACUNIT * 2 : WEAPONBOTTOM;
+
+  psp->sy2 = psp->oldsy2 = psp->sy;
 
   P_SetPsprite(player, ps_weapon, newstate);
 }
@@ -1118,6 +1121,9 @@ void P_MovePsprites(player_t *player)
   const int center_weapon_strict = STRICTMODE(center_weapon);
   int i;
 
+  psp[ps_weapon].oldsx2 = psp[ps_weapon].sx2;
+  psp[ps_weapon].oldsy2 = psp[ps_weapon].sy2;
+
   // a null state means not active
   // drop tic count and possibly change state
   // a -1 tic count never changes
@@ -1176,6 +1182,8 @@ void P_MovePsprites(player_t *player)
 
   player->psprites[ps_flash].sx2 = player->psprites[ps_weapon].sx2;
   player->psprites[ps_flash].sy2 = player->psprites[ps_weapon].sy2;
+  player->psprites[ps_flash].oldsx2 = player->psprites[ps_weapon].oldsx2;
+  player->psprites[ps_flash].oldsy2 = player->psprites[ps_weapon].oldsy2;
 }
 
 //

src/p_pspr.h

@@ -60,6 +60,8 @@ typedef struct pspdef_s
   // [FG] centered weapon sprite
   fixed_t sx2;
   fixed_t sy2;
+  fixed_t oldsx2;
+  fixed_t oldsy2;
 } pspdef_t;
 
 extern int weapon_preferences[2][NUMWEAPONS+1];      // killough 5/2/98

src/p_saveg.c

@@ -771,6 +771,9 @@ static void saveg_read_pspdef_t(pspdef_t *str)
         str->sx2 = str->sx;
         str->sy2 = str->sy;
     }
+
+    str->oldsx2 = str->sx2;
+    str->oldsy2 = str->sy2;
 }
 
 static void saveg_write_pspdef_t(pspdef_t *str)

src/r_main.c

@@ -674,8 +674,6 @@ void R_ExecuteSetViewSize (void)
     }
 
   st_refresh_background = true;
-
-  pspr_interp = false;
 }
 
 //

src/r_things.c

@@ -787,8 +787,6 @@ void R_NearbySprites (void)
 // R_DrawPSprite
 //
 
-boolean pspr_interp = true; // weapon bobbing interpolation
-
 void R_DrawPSprite (pspdef_t *psp)
 {
   fixed_t       tx;
@@ -821,8 +819,21 @@ void R_DrawPSprite (pspdef_t *psp)
   lump = sprframe->lump[0];
   flip = (boolean) sprframe->flip[0];
 
+  fixed_t sx2, sy2;
+
+  if (uncapped && oldleveltime < leveltime)
+  {
+    sx2 = LerpFixed(psp->oldsx2, psp->sx2);
+    sy2 = LerpFixed(psp->oldsy2, psp->sy2);
+  }
+  else
+  {
+    sx2 = psp->sx2;
+    sy2 = psp->sy2;
+  }
+
   // calculate edges of the shape
-  tx = psp->sx2-160*FRACUNIT; // [FG] centered weapon sprite
+  tx = sx2 - 160*FRACUNIT; // [FG] centered weapon sprite
 
   tx -= spriteoffset[lump];
   x1 = (centerxfrac + FixedMul (tx,pspritescale))>>FRACBITS;
@@ -845,7 +856,7 @@ void R_DrawPSprite (pspdef_t *psp)
 
   // killough 12/98: fix psprite positioning problem
   vis->texturemid = (BASEYCENTER<<FRACBITS) /* + FRACUNIT/2 */ -
-                    (psp->sy2-spritetopoffset[lump]); // [FG] centered weapon sprite
+                    (sy2 - spritetopoffset[lump]); // [FG] centered weapon sprite
 
   vis->x1 = x1 < 0 ? 0 : x1;
   vis->x2 = x2 >= viewwidth ? viewwidth-1 : x2;
@@ -883,42 +894,6 @@ void R_DrawPSprite (pspdef_t *psp)
   }
   vis->brightmap = R_BrightmapForState(psp->state - states);
 
-  // interpolation for weapon bobbing
-  if (uncapped)
-  {
-    static int     oldx1, x1_saved;
-    static fixed_t oldtexturemid, texturemid_saved;
-    static int     oldlump = -1;
-    static int     oldgametic = -1;
-
-    if (oldgametic < gametic)
-    {
-      oldx1 = x1_saved;
-      oldtexturemid = texturemid_saved;
-      oldgametic = gametic;
-    }
-
-    x1_saved = vis->x1;
-    texturemid_saved = vis->texturemid;
-
-    if (lump == oldlump && pspr_interp)
-    {
-      int deltax = x2 - vis->x1;
-      vis->x1 = LerpFixed(oldx1, vis->x1);
-      vis->x2 = vis->x1 + deltax;
-      if (vis->x2 >= viewwidth)
-        vis->x2 = viewwidth - 1;
-      vis->texturemid = LerpFixed(oldtexturemid, vis->texturemid);
-    }
-    else
-    {
-      oldx1 = vis->x1;
-      oldtexturemid = vis->texturemid;
-      oldlump = lump;
-      pspr_interp = true;
-    }
-  }
-
   // [crispy] free look
   vis->texturemid += (centery - viewheight/2) * pspriteiscale;
 

src/r_things.h

@@ -39,7 +39,6 @@ extern int64_t sprtopscreen; // [FG] 64-bit integer math
 extern fixed_t pspritescale;
 extern fixed_t pspriteiscale;
 
-extern boolean pspr_interp; // weapon bobbing interpolation
 extern boolean flipcorpses;
 
 extern lighttable_t **spritelights;