From d8d13d44293a58b58d51c3a8e91e3ea76c6d6feb Mon Sep 17 00:00:00 2001
From: aap <aap@papnet.eu>
Date: Sat, 25 Apr 2020 12:16:04 +0200
Subject: [PATCH] added GS alpha test emulation

---
 src/d3d/d3d9render.cpp | 26 ++++++++++++++++++++------
 src/d3d/d3ddevice.cpp  | 20 ++++++++++++++++++++
 src/rwrender.h         |  7 ++++++-
 3 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/src/d3d/d3d9render.cpp b/src/d3d/d3d9render.cpp
index abfb378..494cc92 100644
--- a/src/d3d/d3d9render.cpp
+++ b/src/d3d/d3d9render.cpp
@@ -23,7 +23,7 @@ void defaultRenderCB_Shader(Atomic *atomic, InstanceDataHeader *header) {}
 #else
 
 void
-drawInst(d3d9::InstanceDataHeader *header, d3d9::InstanceData *inst)
+drawInst_simple(d3d9::InstanceDataHeader *header, d3d9::InstanceData *inst)
 {
 	d3d::flushCache();
 	d3ddevice->DrawIndexedPrimitive((D3DPRIMITIVETYPE)header->primType, inst->baseIndex,
@@ -36,27 +36,41 @@ void
 drawInst_GSemu(d3d9::InstanceDataHeader *header, InstanceData *inst)
 {
 	uint32 hasAlpha;
-	int alphafunc;
+	int alphafunc, alpharef, gsalpharef;
 	int zwrite;
 	d3d::getRenderState(D3DRS_ALPHABLENDENABLE, &hasAlpha);
 	if(hasAlpha){
 		zwrite = rw::GetRenderState(rw::ZWRITEENABLE);
 		alphafunc = rw::GetRenderState(rw::ALPHATESTFUNC);
 		if(zwrite){
+			alpharef = rw::GetRenderState(rw::ALPHATESTREF);
+			gsalpharef = rw::GetRenderState(rw::GSALPHATESTREF);
+
 			SetRenderState(rw::ALPHATESTFUNC, rw::ALPHAGREATEREQUAL);
-			drawInst(header, inst);
+			SetRenderState(rw::ALPHATESTREF, gsalpharef);
+			drawInst_simple(header, inst);
 			SetRenderState(rw::ALPHATESTFUNC, rw::ALPHALESS);
 			SetRenderState(rw::ZWRITEENABLE, 0);
-			drawInst(header, inst);
+			drawInst_simple(header, inst);
 			SetRenderState(rw::ZWRITEENABLE, 1);
 			SetRenderState(rw::ALPHATESTFUNC, alphafunc);
+			SetRenderState(rw::ALPHATESTREF, alpharef);
 		}else{
 			SetRenderState(rw::ALPHATESTFUNC, rw::ALPHAALWAYS);
-			drawInst(header, inst);
+			drawInst_simple(header, inst);
 			SetRenderState(rw::ALPHATESTFUNC, alphafunc);
 		}
 	}else
-		drawInst(header, inst);
+		drawInst_simple(header, inst);
+}
+
+void
+drawInst(d3d9::InstanceDataHeader *header, d3d9::InstanceData *inst)
+{
+	if(rw::GetRenderState(rw::GSALPHATEST))
+		drawInst_GSemu(header, inst);
+	else
+		drawInst_simple(header, inst);
 }
 
 void
diff --git a/src/d3d/d3ddevice.cpp b/src/d3d/d3ddevice.cpp
index 99ff50e..a16370c 100644
--- a/src/d3d/d3ddevice.cpp
+++ b/src/d3d/d3ddevice.cpp
@@ -79,6 +79,11 @@ struct RwStateCache {
 	uint32 cullmode;
 	uint32 alphafunc;
 	uint32 alpharef;
+
+	// emulation of PS2 GS
+	bool32 gsalpha;
+	uint32 gsalpharef;
+
 	RwRasterStateCache texstage[MAXNUMSTAGES];
 };
 static RwStateCache rwStateCache;
@@ -548,6 +553,12 @@ setRwRenderState(int32 state, void *pvalue)
 			setRenderState(D3DRS_ALPHAREF, rwStateCache.alpharef);
 		}
 		break;
+	case GSALPHATEST:
+		rwStateCache.gsalpha = value;
+		break;
+	case GSALPHATESTREF:
+		rwStateCache.gsalpharef = value;
+		break;
 	}
 }
 
@@ -605,6 +616,12 @@ getRwRenderState(int32 state)
 	case ALPHATESTREF:
 		val = rwStateCache.alpharef;
 		break;
+	case GSALPHATEST:
+		val = rwStateCache.gsalpha;
+		break;
+	case GSALPHATESTREF:
+		val = rwStateCache.gsalpharef;
+		break;
 	default:
 		val = 0;
 	}
@@ -1326,6 +1343,9 @@ initD3D(void)
 	d3ddevice->SetRenderState(D3DRS_ALPHAREF, 10);
 	rwStateCache.alpharef = 10;
 
+	rwStateCache.gsalpha = 0;
+	rwStateCache.gsalpharef = 128;
+
 	d3ddevice->SetRenderState(D3DRS_FOGENABLE, FALSE);
 	rwStateCache.fogenable = 0;
 	d3ddevice->SetRenderState(D3DRS_FOGTABLEMODE, D3DFOG_LINEAR);
diff --git a/src/rwrender.h b/src/rwrender.h
index 2a19f38..33f094c 100644
--- a/src/rwrender.h
+++ b/src/rwrender.h
@@ -24,7 +24,12 @@ enum RenderState
 
 	// platform specific or opaque?
 	ALPHATESTFUNC,
-	ALPHATESTREF
+	ALPHATESTREF,
+
+	// emulation of PS2 GS alpha test
+	//  in the mode where it still writes color but nor depth
+	GSALPHATEST,
+	GSALPHATESTREF
 };
 
 enum AlphaTestFunc