add smooth texture scrolling from Crispy Doom (#731)

* add smooth texture scrolling from Crispy Doom

* add forgotten baserowoffset initialization

Good catch, eagle eye 😉 @kraflab

* iterate through a list of scrollers separate from the thinker list

* add forgotten parenthesis

* fix another typo (yes, this is a blind lunch break coding session)

* consider friendly suggestions

* Implement a clean interface for cleaning the side scrollers list (@kraflab)
* Allocate scrollers in chunks of 32 (VANILLA limit is 64) (@rfomin)

Thanks!

src/p_saveg.c

@@ -2086,6 +2086,9 @@ void P_UnArchiveWorld (void)
 
 	    si->textureoffset = saveg_read32();
 	    si->rowoffset = saveg_read32();
+	    // [crispy] smooth texture scrolling
+	    si->basetextureoffset = si->textureoffset;
+	    si->baserowoffset = si->rowoffset;
 
             si->toptexture = saveg_read16();
             si->bottomtexture = saveg_read16();

src/p_setup.c

@@ -577,6 +577,9 @@ void P_LoadSideDefs2(int lump)
 
       sd->textureoffset = SHORT(msd->textureoffset)<<FRACBITS;
       sd->rowoffset = SHORT(msd->rowoffset)<<FRACBITS;
+      // [crispy] smooth texture scrolling
+      sd->basetextureoffset = sd->textureoffset;
+      sd->baserowoffset = sd->rowoffset;
 
       // killough 4/4/98: allow sidedef texture names to be overloaded
       // killough 4/11/98: refined to allow colormaps to work as wall

src/p_spec.c

@@ -56,6 +56,7 @@
 #include "r_draw.h"  // R_SetFuzzPosTic
 #include "r_sky.h"   // R_GetSkyColor
 #include "m_swap.h"
+#include "i_video.h" // [FG] uncapped
 
 //
 // Animating textures and planes
@@ -2591,8 +2592,10 @@ void T_Scroll(scroll_t *s)
 
     case sc_side:                   // killough 3/7/98: Scroll wall texture
         side = sides + s->affectee;
-        side->textureoffset += dx;
+        side->basetextureoffset += dx;
-        side->rowoffset += dy;
+        side->baserowoffset += dy;
+        side->textureoffset = side->basetextureoffset;
+        side->rowoffset = side->baserowoffset;
         break;
 
     case sc_floor:                  // killough 3/7/98: Scroll floor texture
@@ -2638,6 +2641,47 @@ void T_Scroll(scroll_t *s)
     }
 }
 
+// [crispy] smooth texture scrolling
+
+static int maxsidescrollers, numsidescrollers;
+static scroll_t **sidescrollers;
+
+static void P_AddSideScroller (scroll_t *s)
+{
+  if (numsidescrollers == maxsidescrollers)
+  {
+    maxsidescrollers = maxsidescrollers ? 2 * maxsidescrollers : 32;
+    sidescrollers = I_Realloc(sidescrollers, maxsidescrollers * sizeof(*sidescrollers));
+  }
+  sidescrollers[numsidescrollers++] = s;
+}
+
+static void P_FreeSideScrollers (void)
+{
+  maxsidescrollers = 0;
+  numsidescrollers = 0;
+  if (sidescrollers)
+    free(sidescrollers);
+  sidescrollers = NULL;
+}
+
+void R_InterpolateTextureOffsets (void)
+{
+  if (uncapped && leveltime > oldleveltime)
+  {
+    int i;
+
+    for (i = 0; i < numsidescrollers; i++)
+    {
+      scroll_t *s = sidescrollers[i];
+      side_t *side = sides + s->affectee;
+
+      side->textureoffset = side->basetextureoffset + FixedMul(s->dx, fractionaltic);
+      side->rowoffset = side->baserowoffset + FixedMul(s->dy, fractionaltic);
+    }
+  }
+}
+
 //
 // Add_Scroller()
 //
@@ -2671,6 +2715,9 @@ static void Add_Scroller(int type, fixed_t dx, fixed_t dy,
       sectors[control].floorheight + sectors[control].ceilingheight;
   s->affectee = affectee;
   P_AddThinker(&s->thinker);
+
+  if (type == sc_side)
+    P_AddSideScroller(s);
 }
 
 // Adds wall scroller. Scroll amount is rotated with respect to wall's
@@ -2710,6 +2757,8 @@ static void P_SpawnScrollers(void)
   int i;
   line_t *l = lines;
 
+  P_FreeSideScrollers();
+
   for (i=0;i<numlines;i++,l++)
     {
       fixed_t dx = l->dx >> SCROLL_SHIFT;  // direction and speed of scrolling

src/r_defs.h

@@ -189,6 +189,10 @@ typedef struct
 
   int special;
 
+  // [crispy] smooth texture scrolling
+  fixed_t basetextureoffset;
+  fixed_t baserowoffset;
+
 } side_t;
 
 //

src/r_main.c

@@ -814,6 +814,9 @@ void R_RenderPlayerView (player_t* player)
   // check for new console commands.
   NetUpdate ();
 
+  // [crispy] smooth texture scrolling
+  R_InterpolateTextureOffsets();
+
   // The head node is the last node output.
   R_RenderBSPNode (numnodes-1);
     

src/r_main.h

@@ -123,6 +123,9 @@ void R_InitLightTables(void);                // killough 8/9/98
 extern boolean setsizeneeded;
 void R_ExecuteSetViewSize(void);
 
+// [crispy] smooth texture scrolling
+void R_InterpolateTextureOffsets (void);
+
 #endif
 
 //----------------------------------------------------------------------------