From 67b0e022364307332dd0383c22dfca5fb3c14467 Mon Sep 17 00:00:00 2001
From: skyjake <skyjake@3894b877-cc0d-0410-b400-92b7ed5dc389>
Date: Tue, 12 Aug 2003 22:47:55 +0000
Subject: [PATCH] Added subtract and reverse subtract blending modes

---
 doomsday/Include/dglib.h    |  4 ++++
 doomsday/Include/r_model.h  | 20 +++++++++++---------
 doomsday/Src/drOpenGL/ext.c | 21 +++++++++++++++------
 3 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/doomsday/Include/dglib.h b/doomsday/Include/dglib.h
index 315863fb8f..168213933c 100644
--- a/doomsday/Include/dglib.h
+++ b/doomsday/Include/dglib.h
@@ -125,6 +125,7 @@ enum
 	DGL_PALETTED_GENMIPS,
 	DGL_MODULATE_ADD_COMBINE,
 	DGL_MODULATE_TEXTURE,
+	DGL_BLENDING_OP,
 
 	DGL_TEXTURE0					= 0x5F00,
 	DGL_TEXTURE1,
@@ -147,6 +148,9 @@ enum
 	DGL_SRC_ALPHA,
 	DGL_ONE_MINUS_SRC_ALPHA,
 	DGL_SRC_ALPHA_SATURATE,
+	DGL_ADD,
+	DGL_SUBTRACT,
+	DGL_REVERSE_SUBTRACT,
 
 	// Comparative functions
 	DGL_ALWAYS						= 0x7000,
diff --git a/doomsday/Include/r_model.h b/doomsday/Include/r_model.h
index fa6611a2b1..de52af8c95 100644
--- a/doomsday/Include/r_model.h
+++ b/doomsday/Include/r_model.h
@@ -25,15 +25,17 @@
 #define MFF_DARKSHADOW			0x2000
 #define MFF_IDSKIN				0x4000	// Mobj id -> skin in skin range
 #define MFF_DISABLE_Z_WRITE		0x8000
-#define MFF_NO_DISTANCE_CHECK	0x10000
-#define MFF_SELSKIN				0x20000
-#define MFF_PARTICLE_SUB1		0x40000	// Sub1 center is particle origin.
-#define MFF_NO_PARTICLES		0x80000	// No particles for this object.
-#define MFF_SHINY_SPECULAR		0x100000 // Shiny skin rendered as additive.
-#define MFF_SHINY_LIT			0x200000 // Shiny skin is not fullbright.
-#define MFF_IDFRAME				0x400000 // Mobj id -> frame in frame range
-#define MFF_IDANGLE				0x800000 // Mobj id -> static angle offset
-#define MFF_DIM					0x1000000 // Never fullbright.
+#define MFF_NO_DISTANCE_CHECK	0x00010000
+#define MFF_SELSKIN				0x00020000
+#define MFF_PARTICLE_SUB1		0x00040000 // Sub1 center is particle origin.
+#define MFF_NO_PARTICLES		0x00080000 // No particles for this object.
+#define MFF_SHINY_SPECULAR		0x00100000 // Shiny skin rendered as additive.
+#define MFF_SHINY_LIT			0x00200000 // Shiny skin is not fullbright.
+#define MFF_IDFRAME				0x00400000 // Mobj id -> frame in frame range
+#define MFF_IDANGLE				0x00800000 // Mobj id -> static angle offset
+#define MFF_DIM					0x01000000 // Never fullbright.
+#define MFF_SUBTRACT			0x02000000 // Subtract blending.
+#define MFF_REVERSE_SUBTRACT	0x04000000 // Reverse subtract blending.
 
 typedef struct
 {
diff --git a/doomsday/Src/drOpenGL/ext.c b/doomsday/Src/drOpenGL/ext.c
index 8addfee9a2..753f101a01 100644
--- a/doomsday/Src/drOpenGL/ext.c
+++ b/doomsday/Src/drOpenGL/ext.c
@@ -25,6 +25,7 @@
 // PUBLIC DATA DEFINITIONS -------------------------------------------------
 
 int extMultiTex;
+int extBlendSub;
 int	extTexEnvComb;
 int	extNvTexEnvComb;
 int	extAtiTexEnvComb;
@@ -32,13 +33,15 @@ int	extAniso;
 int	extLockArray;
 int extGenMip;
 
-PFNGLCLIENTACTIVETEXTUREPROC	glClientActiveTextureARB = 0;
-PFNGLACTIVETEXTUREARBPROC		glActiveTextureARB = 0;
-PFNGLMULTITEXCOORD2FARBPROC		glMultiTexCoord2fARB = 0;
-PFNGLMULTITEXCOORD2FVARBPROC	glMultiTexCoord2fvARB = 0;
+PFNGLCLIENTACTIVETEXTUREPROC	glClientActiveTextureARB;
+PFNGLACTIVETEXTUREARBPROC		glActiveTextureARB;
+PFNGLMULTITEXCOORD2FARBPROC		glMultiTexCoord2fARB;
+PFNGLMULTITEXCOORD2FVARBPROC	glMultiTexCoord2fvARB;
 
-PFNGLLOCKARRAYSEXTPROC			glLockArraysEXT = 0;
-PFNGLUNLOCKARRAYSEXTPROC		glUnlockArraysEXT = 0;
+PFNGLBLENDEQUATIONEXTPROC		glBlendEquationEXT;
+
+PFNGLLOCKARRAYSEXTPROC			glLockArraysEXT;
+PFNGLUNLOCKARRAYSEXTPROC		glUnlockArraysEXT;
 
 // PRIVATE DATA DEFINITIONS ------------------------------------------------
 
@@ -111,6 +114,12 @@ void initExtensions(void)
 	query("GL_EXT_shared_texture_palette", &sharedPalExtAvailable);
 	query("GL_EXT_texture_filter_anisotropic", &extAniso);
 
+	// EXT_blend_subtract
+	if(query("GL_EXT_blend_subtract", &extBlendSub))
+	{
+		GETPROC( glBlendEquationEXT );
+	}
+
 	// ARB_texture_env_combine
 	if(!query("GL_ARB_texture_env_combine", &extTexEnvComb))
 	{