From 10e4c3e121bb65c0ff898f21ab365e442f6a67b1 Mon Sep 17 00:00:00 2001
From: NY00123 <ny00@outlook.com>
Date: Sun, 19 Apr 2020 21:15:57 +0300
Subject: [PATCH] sw/src/draw.cpp: Import from Duke3D the Polymost shadow
 drawing hacks

---
 source/sw/src/draw.cpp | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/source/sw/src/draw.cpp b/source/sw/src/draw.cpp
index b362d74c5..9d8fff331 100644
--- a/source/sw/src/draw.cpp
+++ b/source/sw/src/draw.cpp
@@ -368,7 +368,7 @@ DoVoxelShadow(SPRITEp tspr)
 #endif
 
 void
-DoShadows(tspriteptr_t tsp, int viewz)
+DoShadows(tspriteptr_t tsp, int viewz, SWBOOL mirror)
 {
     tspriteptr_t New = &tsprite[spritesortcnt];
     USERp tu = User[tsp->owner];
@@ -456,6 +456,28 @@ DoShadows(tspriteptr_t tsp, int viewz)
     New->xrepeat = xrepeat;
     New->yrepeat = yrepeat;
 
+#ifdef USE_OPENGL
+    if (videoGetRenderMode() >= REND_POLYMOST)
+    {
+        if (tilehasmodelorvoxel(tsp->picnum,tsp->pal))
+        {
+            New->yrepeat = 0;
+            // cstat:    trans reverse
+            // clipdist: tell mdsprite.cpp to use Z-buffer hacks to hide overdraw issues
+            New->clipdist |= TSPR_FLAGS_MDHACK;
+            New->cstat |= 512;
+        }
+        else
+        {
+            int const camang = mirror ? NORM_ANGLE(2048 - Player[screenpeek].siang) : Player[screenpeek].siang;
+            vec2_t const ofs = { sintable[NORM_ANGLE(camang+512)]>>11, sintable[NORM_ANGLE(camang)]>>11};
+
+            New->x += ofs.x;
+            New->y += ofs.y;
+        }
+    }
+#endif
+
     // Check for voxel items and use a round generic pic if so
     //DoVoxelShadow(New);
 
@@ -758,7 +780,7 @@ analyzesprites(int viewx, int viewy, int viewz, SWBOOL mirror)
 
             if (r_shadows && TEST(tu->Flags, SPR_SHADOW))
             {
-                DoShadows(tsp, viewz);
+                DoShadows(tsp, viewz, mirror);
             }
 
             //#define UK_VERSION 1