From b341cacb0aecad90dcb671466208b7b66548f752 Mon Sep 17 00:00:00 2001
From: Sryder <sryder13@gmail.com>
Date: Mon, 19 Oct 2020 11:57:12 +0100
Subject: [PATCH] Subtractive translation map

---
 src/dehacked.c         | 3 +++
 src/hardware/hw_main.c | 1 +
 src/p_mobj.h           | 1 +
 src/p_pspr.h           | 2 ++
 src/r_draw.c           | 3 ++-
 5 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/dehacked.c b/src/dehacked.c
index b57d52c7f..c564174c2 100644
--- a/src/dehacked.c
+++ b/src/dehacked.c
@@ -11124,6 +11124,7 @@ struct {
 	{"FF_TRANS80",FF_TRANS80},
 	{"FF_TRANS90",FF_TRANS90},
 	{"FF_TRANSADD",FF_TRANSADD},
+	{"FF_TRANSSUB",FF_TRANSSUB},
 	// compatibility
 	// Transparency for SOCs is pre-shifted
 	{"TR_TRANS10",tr_trans10<<FF_TRANSSHIFT},
@@ -11136,6 +11137,7 @@ struct {
 	{"TR_TRANS80",tr_trans80<<FF_TRANSSHIFT},
 	{"TR_TRANS90",tr_trans90<<FF_TRANSSHIFT},
 	{"TR_TRANSADD",tr_transadd<<FF_TRANSSHIFT},
+	{"TR_TRANSSUB",tr_transsub<<FF_TRANSSHIFT},
 	// Transparency for Lua is not, unless capitalized as above.
 	{"tr_trans10",tr_trans10},
 	{"tr_trans20",tr_trans20},
@@ -11147,6 +11149,7 @@ struct {
 	{"tr_trans80",tr_trans80},
 	{"tr_trans90",tr_trans90},
 	{"tr_transadd",tr_transadd},
+	{"tr_transsub",tr_transsub},
 	{"NUMTRANSMAPS",NUMTRANSMAPS},
 
 	// Type of levels
diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 135b129f5..4d5b136cf 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -782,6 +782,7 @@ FBITFIELD HWR_TranstableToAlpha(INT32 transtablenum, FSurfaceInfo *pSurf)
 		case tr_trans80 : pSurf->PolyColor.s.alpha = 0x33;return  PF_Translucent;
 		case tr_trans90 : pSurf->PolyColor.s.alpha = 0x19;return  PF_Translucent;
 		case tr_transadd : pSurf->PolyColor.s.alpha = 0xFF;return PF_Additive;
+		case tr_transsub : pSurf->PolyColor.s.alpha = 0xFF;return PF_Substractive;
 	}
 	return PF_Translucent;
 }
diff --git a/src/p_mobj.h b/src/p_mobj.h
index 04a75c85e..6ffa393aa 100644
--- a/src/p_mobj.h
+++ b/src/p_mobj.h
@@ -269,6 +269,7 @@ typedef enum
 	MFD_TRANS80				= 0x0080,
 	MFD_TRANS90				= 0x0090,
 	MFD_TRANSADD			= 0x00A0,
+	MFD_TRANSSUB			= 0x00B0,
 	MFD_TRANSMASK			= 0x00F0,
 	// Brightness override flags
 	MFD_FULLBRIGHT			= 0x0100,
diff --git a/src/p_pspr.h b/src/p_pspr.h
index eaa469cd7..cbc1a845f 100644
--- a/src/p_pspr.h
+++ b/src/p_pspr.h
@@ -60,6 +60,7 @@
 #define FF_TRANS80 (tr_trans80<<FF_TRANSSHIFT)
 #define FF_TRANS90 (tr_trans90<<FF_TRANSSHIFT)
 #define FF_TRANSADD (tr_transadd<<FF_TRANSSHIFT)
+#define FF_TRANSSUB (tr_transsub<<FF_TRANSSHIFT)
 
 /// \brief Frame flags: frame always appears full bright (mutually exclusive with below, currently takes priority)
 #define FF_FULLBRIGHT 0x00100000
@@ -101,6 +102,7 @@ typedef enum
 	tr_trans80,
 	tr_trans90,
 	tr_transadd,
+	tr_transsub,
 	NUMTRANSMAPS
 } transnum_t;
 
diff --git a/src/r_draw.c b/src/r_draw.c
index 703462662..3d806eaf0 100644
--- a/src/r_draw.c
+++ b/src/r_draw.c
@@ -81,7 +81,7 @@ UINT8 *dc_source;
 // -----------------------
 // translucency stuff here
 // -----------------------
-#define NUMTRANSTABLES 10 // how many translucency tables are used
+#define NUMTRANSTABLES 11 // how many translucency tables are used
 
 UINT8 *transtables; // translucency tables
 
@@ -173,6 +173,7 @@ void R_InitTranslationTables(void)
 	W_ReadLump(W_GetNumForName("TRANS80"), transtables+0x70000);
 	W_ReadLump(W_GetNumForName("TRANS90"), transtables+0x80000);
 	W_ReadLump(W_GetNumForName("TRANSADD"),transtables+0x90000);
+	W_ReadLump(W_GetNumForName("TRANSSUB"),transtables+0xA0000);
 }
 
 /**	\brief	Retrieves a translation colormap from the cache.