From 13dbe7d3a3e2c4b59a098da88738829f52b9144c Mon Sep 17 00:00:00 2001
From: Nevur <apophycens@gmail.com>
Date: Sun, 5 Mar 2017 18:53:34 +0100
Subject: [PATCH] Fixed issue with vertical offsets being broken. Add a
 vertical flip variant for the translucent column drawer. Translucency is now
 properly distributed: 0.00 leads to no render at all, 0.1 to TRANS10, ...,
 0.9 to TRANS90, 1 to regular column drawer.

---
 src/r_data.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/src/r_data.c b/src/r_data.c
index dbe896360..1ca6472d3 100644
--- a/src/r_data.c
+++ b/src/r_data.c
@@ -219,7 +219,7 @@ static inline void R_DrawTransColumnInCache(column_t *patch, UINT8 *cache, texpa
 {
 	INT32 count, position;
 	UINT8 *source, *dest;
-	UINT8 *mytransmap = transtables + ((8*(originPatch->alpha)/255) << FF_TRANSSHIFT);
+	UINT8 *mytransmap = transtables + ((8*(originPatch->alpha) + 255/8)/(255 - 255/11) << FF_TRANSSHIFT); // The equation's not exact but it works as intended. I'll call it a day for now.
 	INT32 topdelta, prevdelta = -1;
     INT32 originy = originPatch->originy;
 
@@ -246,17 +246,53 @@ static inline void R_DrawTransColumnInCache(column_t *patch, UINT8 *cache, texpa
         dest = cache + position;
 		if (count > 0)
         {
-			for (; dest < cache + position + count; ++source)
-				//*dest++ = transtables[(*source)<<8 + *dest];
-				*dest++ = *(mytransmap + ((*source)<<8) + (*dest));
-				//*dest++ = *source;
+			for (; dest < cache + position + count; source++, dest++)
+				*dest = *(mytransmap + ((*dest)<<8) + (*source));
         }
 
 		patch = (column_t *)((UINT8 *)patch + patch->length + 4);
 	}
 }
 
+static inline void R_DrawTransFlippedColumnInCache(column_t *patch, UINT8 *cache, texpatch_t *originPatch, INT32 cacheheight, INT32 patchheight)
+{
+	INT32 count, position;
+	UINT8 *source, *dest;
+	UINT8 *mytransmap = transtables + ((8*(originPatch->alpha) + 255/8)/(255 - 255/11) << FF_TRANSSHIFT); // The equation's not exact but it works as intended. I'll call it a day for now.
+	INT32 topdelta, prevdelta = -1;
+    INT32 originy = originPatch->originy;
 
+	while (patch->topdelta != 0xff)
+	{
+		topdelta = patch->topdelta;
+		if (topdelta <= prevdelta)
+			topdelta += prevdelta;
+		prevdelta = topdelta;
+		topdelta = patchheight-patch->length-topdelta;
+		source = (UINT8 *)patch + 2 + patch->length; // patch + 3 + (patch->length-1)
+		count = patch->length;
+		position = originy + topdelta;
+
+		if (position < 0)
+		{
+			count += position;
+			source += position; // start further UP the column
+			position = 0;
+		}
+
+		if (position + count > cacheheight)
+			count = cacheheight - position;
+
+		dest = cache + position;
+		if (count > 0)
+		{
+			for (; dest < cache + position + count; --source, dest++)
+				*dest = *(mytransmap + ((*dest)<<8) + (*source));
+		}
+
+		patch = (column_t *)((UINT8 *)patch + patch->length + 4);
+	}
+}
 
 //
 // R_GenerateTexture
@@ -371,10 +407,12 @@ static UINT8 *R_GenerateTexture(size_t texnum)
 	for (i = 0, patch = texture->patches; i < texture->patchcount; i++, patch++)
 	{
 	    static void (*ColumnDrawerPointer)(column_t *, UINT8 *, texpatch_t *, INT32, INT32); // Column drawing function pointer.
-	    if (patch->style == AST_TRANSLUCENT)
+	    if ((patch->style == AST_TRANSLUCENT) && (patch->alpha <= (10*255/11))) // Alpha style set to translucent? Is the alpha small enough for translucency?
         {
+            if (patch->alpha < 255/11) // Is the patch way too translucent? Don't render then.
+                continue;
             if (patch->flip & 2)
-                ColumnDrawerPointer = &R_DrawTransColumnInCache;
+                ColumnDrawerPointer = &R_DrawTransFlippedColumnInCache;
             else
                 ColumnDrawerPointer = &R_DrawTransColumnInCache;
         }