From 1504e19cf894fd00a434d17f9cc4d2bbc1725f87 Mon Sep 17 00:00:00 2001
From: Mitchell Richters <mjr4077au@gmail.com>
Date: Thu, 26 Nov 2020 19:15:49 +1100
Subject: [PATCH] - Exhumed: Add sprite interpolation to `analyzesprites()`.

---
 source/exhumed/src/exhumed.cpp | 17 +++++++++++++++++
 source/exhumed/src/view.cpp    | 21 ++++++++++++++++++---
 source/exhumed/src/view.h      |  6 ++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/source/exhumed/src/exhumed.cpp b/source/exhumed/src/exhumed.cpp
index f905fd4e9..227370089 100644
--- a/source/exhumed/src/exhumed.cpp
+++ b/source/exhumed/src/exhumed.cpp
@@ -174,6 +174,8 @@ int nTimeLimit;
 
 int bVanilla = 0;
 
+Loc oldLocs[MAXSPRITES];
+
 void DebugOut(const char *fmt, ...)
 {
 #ifdef _DEBUG
@@ -260,10 +262,25 @@ double calc_smoothratio()
     return I_GetTimeFrac() * MaxSmoothRatio;
 }
 
+static void recordoldspritepos()
+{
+    for (int i = 0; i < MAXSPRITES; i++)
+    {
+        auto* spr = &sprite[i];
+        Loc* oldLoc = &oldLocs[i];
+        oldLoc->x = spr->x;
+        oldLoc->y = spr->y;
+        oldLoc->z = spr->z;
+        oldLoc->ang = spr->ang;
+    }
+}
+
 void GameMove(void)
 {
     FixPalette();
 
+    recordoldspritepos();
+
     if (currentLevel->levelNumber == kMap20)
     {
         if (lCountDown <= 0)
diff --git a/source/exhumed/src/view.cpp b/source/exhumed/src/view.cpp
index b6eb814fd..0ebf22225 100644
--- a/source/exhumed/src/view.cpp
+++ b/source/exhumed/src/view.cpp
@@ -121,8 +121,24 @@ void viewRestoreInterpolations(void)  //Stick at end of drawscreen
 }
 
 // NOTE - not to be confused with Ken's analyzesprites()
-static void analyzesprites()
+static void analyzesprites(double const smoothratio)
 {
+    tspritetype *pTSprite;
+
+    for (int i = 0; i < spritesortcnt; i++) {
+        pTSprite = &tsprite[i];
+
+        if (pTSprite->owner != -1)
+        {
+            // interpolate sprite position
+            Loc* oldLoc = &oldLocs[pTSprite->owner];
+            pTSprite->x = oldLoc->x + MulScale(pTSprite->x - oldLoc->x, smoothratio, 16);
+            pTSprite->y = oldLoc->y + MulScale(pTSprite->y - oldLoc->y, smoothratio, 16);
+            pTSprite->z = oldLoc->z + MulScale(pTSprite->z - oldLoc->z, smoothratio, 16);
+            pTSprite->ang = oldLoc->ang + MulScale(((pTSprite->ang - oldLoc->ang + 1024) & 0x7FF) - 1024, smoothratio, 16);
+        }
+    }
+
     short nPlayerSprite = PlayerList[nLocalPlayer].nSprite;
 
     int var_38 = 20;
@@ -142,7 +158,6 @@ static void analyzesprites()
     int nAngle = (2048 - pPlayerSprite->ang) & kAngleMask;
 
     int nTSprite;
-    tspritetype *pTSprite;
 
 //	int var_20 = var_24;
 
@@ -398,7 +413,7 @@ void DrawView(double smoothRatio, bool sceneonly)
         }
 
         renderDrawRoomsQ16(nCamerax, nCameray, viewz, nCameraa.asq16(), nCamerapan.asq16(), nSector);
-        analyzesprites();
+        analyzesprites(smoothRatio);
         renderDrawMasks();
 
         if (HavePLURemap())
diff --git a/source/exhumed/src/view.h b/source/exhumed/src/view.h
index 1acc748c3..c46eb6f1c 100644
--- a/source/exhumed/src/view.h
+++ b/source/exhumed/src/view.h
@@ -46,6 +46,12 @@ extern short bTouchFloor;
 extern short nChunkTotal;
 extern int gFov;
 
+struct Loc
+{
+	int x, y, z, ang;
+};
+extern Loc oldLocs[MAXSPRITES];
+
 static inline int angle_interpolate16(int a, int b, int smooth)
 {
     return a + mulscale16(((b+1024-a)&2047)-1024, smooth);