From ce4fee737352f2d23122d5f269d306bf7d4a4a09 Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Sun, 11 Sep 2022 21:14:47 -0700
Subject: [PATCH] softgpu: Refactor triangle cull processing.

---
 GPU/Software/TransformUnit.cpp | 54 ++++++++++++----------------------
 GPU/Software/TransformUnit.h   |  7 +++++
 2 files changed, 25 insertions(+), 36 deletions(-)

diff --git a/GPU/Software/TransformUnit.cpp b/GPU/Software/TransformUnit.cpp
index 28a91a7a8c..aa31e3edf6 100644
--- a/GPU/Software/TransformUnit.cpp
+++ b/GPU/Software/TransformUnit.cpp
@@ -447,12 +447,6 @@ SoftDirty TransformUnit::GetDirty() {
 	return binner_->GetDirty();
 }
 
-enum class CullType {
-	CW,
-	CCW,
-	OFF,
-};
-
 void TransformUnit::SubmitPrimitive(const void* vertices, const void* indices, GEPrimitiveType prim_type, int vertex_count, u32 vertex_type, int *bytesRead, SoftwareDrawEngine *drawEngine)
 {
 	VertexDecoder &vdecoder = *drawEngine->FindVertexDecoder(vertex_type);
@@ -541,17 +535,8 @@ void TransformUnit::SubmitPrimitive(const void* vertices, const void* indices, G
 
 				switch (prim_type) {
 				case GE_PRIM_TRIANGLES:
-				{
-					if (cullType == CullType::OFF) {
-						Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[2], *binner_);
-						Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[2], *binner_);
-					} else if (cullType == CullType::CW) {
-						Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[2], *binner_);
-					} else {
-						Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[2], *binner_);
-					}
+					SendTriangle(cullType, &data_[0]);
 					break;
-				}
 
 				case GE_PRIM_LINES:
 					Clipper::ProcessLine(data_[0], data_[1], *binner_);
@@ -688,16 +673,9 @@ void TransformUnit::SubmitPrimitive(const void* vertices, const void* indices, G
 					continue;
 				}
 
-				if (cullType == CullType::OFF) {
-					Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[provoking_index], *binner_);
-					Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[provoking_index], *binner_);
-				} else if ((!(int)cullType) ^ ((data_index_ - 1) % 2)) {
-					// We need to reverse the vertex order for each second primitive,
-					// but we additionally need to do that for every primitive if CCW cullmode is used.
-					Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[provoking_index], *binner_);
-				} else {
-					Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[provoking_index], *binner_);
-				}
+				int wind = (data_index_ - 1) % 2;
+				CullType altCullType = cullType == CullType::OFF ? cullType : CullType((int)cullType ^ wind);
+				SendTriangle(altCullType, &data_[0], provoking_index);
 			}
 			break;
 		}
@@ -764,16 +742,9 @@ void TransformUnit::SubmitPrimitive(const void* vertices, const void* indices, G
 					continue;
 				}
 
-				if (cullType == CullType::OFF) {
-					Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[provoking_index], *binner_);
-					Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[provoking_index], *binner_);
-				} else if ((!(int)cullType) ^ ((data_index_ - 1) % 2)) {
-					// We need to reverse the vertex order for each second primitive,
-					// but we additionally need to do that for every primitive if CCW cullmode is used.
-					Clipper::ProcessTriangle(data_[2], data_[1], data_[0], data_[provoking_index], *binner_);
-				} else {
-					Clipper::ProcessTriangle(data_[0], data_[1], data_[2], data_[provoking_index], *binner_);
-				}
+				int wind = (data_index_ - 1) % 2;
+				CullType altCullType = cullType == CullType::OFF ? cullType : CullType((int)cullType ^ wind);
+				SendTriangle(altCullType, &data_[0], provoking_index);
 			}
 			break;
 		}
@@ -784,6 +755,17 @@ void TransformUnit::SubmitPrimitive(const void* vertices, const void* indices, G
 	}
 }
 
+void TransformUnit::SendTriangle(CullType cullType, const VertexData *verts, int provoking) {
+	if (cullType == CullType::OFF) {
+		Clipper::ProcessTriangle(verts[0], verts[1], verts[2], verts[provoking], *binner_);
+		Clipper::ProcessTriangle(verts[2], verts[1], verts[0], verts[provoking], *binner_);
+	} else if (cullType == CullType::CW) {
+		Clipper::ProcessTriangle(verts[2], verts[1], verts[0], verts[provoking], *binner_);
+	} else {
+		Clipper::ProcessTriangle(verts[0], verts[1], verts[2], verts[provoking], *binner_);
+	}
+}
+
 void TransformUnit::Flush(const char *reason) {
 	binner_->Flush(reason);
 	GPUDebug::NotifyDraw();
diff --git a/GPU/Software/TransformUnit.h b/GPU/Software/TransformUnit.h
index faa761639c..ec5883e8e2 100644
--- a/GPU/Software/TransformUnit.h
+++ b/GPU/Software/TransformUnit.h
@@ -37,6 +37,12 @@ typedef Vec4<float> ClipCoords; // Range: -w <= x/y/z <= w
 class BinManager;
 struct TransformState;
 
+enum class CullType {
+	CW = 0,
+	CCW = 1,
+	OFF = 2,
+};
+
 struct ScreenCoords
 {
 	ScreenCoords() {}
@@ -133,6 +139,7 @@ public:
 
 private:
 	VertexData ReadVertex(VertexReader &vreader, const TransformState &lstate, bool &outside_range_flag);
+	void SendTriangle(CullType cullType, const VertexData *verts, int provoking = 2);
 
 	u8 *decoded_ = nullptr;
 	BinManager *binner_ = nullptr;