From 42f9443de119bf6c2e3160978ba4f9dd7a6c2f43 Mon Sep 17 00:00:00 2001
From: James R <justsomejames2@gmail.com>
Date: Sun, 16 Oct 2022 18:06:02 -0700
Subject: [PATCH] UDMF: Add back #900 and #901 additive, subtractive special
 alpha values for FOFs

Fix fourth digit blend mode being off by one.

see ebe38ff518
---
 src/p_setup.c | 15 +++++++++++++--
 src/p_spec.c  |  5 +++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/p_setup.c b/src/p_setup.c
index 2e9c0830d..d1433a7a4 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -3838,10 +3838,21 @@ static void P_SetBinaryFOFAlpha(line_t *line)
 	if (sides[line->sidenum[0]].toptexture > 0)
 	{
 		line->args[1] = sides[line->sidenum[0]].toptexture;
-		if (sides[line->sidenum[0]].toptexture >= 1001)
+
+		if (line->args[1] == 901) // additive special
+		{
+			line->args[1] = 0xff;
+			line->args[2] = TMB_ADD;
+		}
+		else if (line->args[1] == 902) // subtractive special
+		{
+			line->args[1] = 0xff;
+			line->args[2] = TMB_SUBTRACT;
+		}
+		else if (line->args[1] >= 1001) // fourth digit
 		{
-			line->args[2] = (sides[line->sidenum[0]].toptexture/1000);
 			line->args[1] %= 1000;
+			line->args[2] = (sides[line->sidenum[0]].toptexture/1000) + 1; // becomes an AST
 		}
 	}
 	else
diff --git a/src/p_spec.c b/src/p_spec.c
index 8db26f249..25d75f3ff 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -5102,8 +5102,9 @@ static ffloor_t *P_AddFakeFloor(sector_t *sec, sector_t *sec2, line_t *master, I
 		else th = th->next;
 	}
 
-	fflr->alpha = max(0, min(0xff, alpha));
-	if (fflr->alpha < 0xff || flags & FOF_SPLAT)
+	//fflr->alpha = max(0, min(0xff, alpha));
+	fflr->alpha = alpha;
+	if (blendmode != TMB_TRANSLUCENT || fflr->alpha != 0xff || flags & FOF_SPLAT)
 	{
 		fflr->fofflags |= FOF_TRANSLUCENT;
 		fflr->spawnflags = fflr->fofflags;