From c953d919e69fd512312a0683346a635997fae79e Mon Sep 17 00:00:00 2001
From: Roman Fomin <rfomin@gmail.com>
Date: Wed, 18 May 2022 14:15:11 +0700
Subject: [PATCH] interpolation for weapon bobbing from PrBoom+ (#554)

---
 Source/r_things.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Source/r_things.c b/Source/r_things.c
index c45d06c7..d1f0ee1a 100644
--- a/Source/r_things.c
+++ b/Source/r_things.c
@@ -750,6 +750,39 @@ void R_DrawPSprite (pspdef_t *psp)
   else
     vis->colormap = spritelights[MAXLIGHTSCALE-1];  // local light
 
+  // 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)
+    {
+      int deltax = vis->x2 - vis->x1;
+      vis->x1 = oldx1 + FixedMul(vis->x1 - oldx1, fractionaltic);
+      vis->x2 = vis->x1 + deltax;
+      vis->texturemid = oldtexturemid + FixedMul(vis->texturemid - oldtexturemid, fractionaltic);
+    }
+    else
+    {
+      oldx1 = vis->x1;
+      oldtexturemid = vis->texturemid;
+      oldlump = lump;
+    }
+  }
+
   R_DrawVisSprite(vis, vis->x1, vis->x2);
 }