From 6f999c77f147f2301ad648b5339db17d03847a37 Mon Sep 17 00:00:00 2001
From: Nicholas Estelami <NEstelami@users.noreply.github.com>
Date: Sun, 30 Apr 2023 20:13:10 -0400
Subject: Fixed improperly extracted vertices (#281)

---
 ZAPD/ZDisplayList.cpp | 44 +++++++++++++++++++++++++++++++++++++++++++-
 ZAPD/ZDisplayList.h   |  3 +++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/ZAPD/ZDisplayList.cpp b/ZAPD/ZDisplayList.cpp
index 3b50c1f..50fd09f 100644
--- a/ZAPD/ZDisplayList.cpp
+++ b/ZAPD/ZDisplayList.cpp
@@ -1642,7 +1642,12 @@ static int32_t GfxdCallback_Vtx(uint32_t seg, int32_t count)
 				vtxList.push_back(vtx);
 				currentPtr += 16;
 			}
-			self->vertices[vtxOffset] = vtxList;
+
+			bool keyAlreadyOccupied = self->vertices.find(vtxOffset) != self->vertices.end();
+
+			// In some cases a vtxList already exists at vtxOffset. Only override the existing list if the new one is bigger.
+			if (!keyAlreadyOccupied || (keyAlreadyOccupied && vtxList.size() > self->vertices[vtxOffset].size()))
+				self->vertices[vtxOffset] = vtxList;
 		}
 	}
 
@@ -1954,9 +1959,46 @@ std::string ZDisplayList::ProcessGfxDis([[maybe_unused]] const std::string& pref
 	gfxd_execute();                               // generate display list
 	sourceOutput += outputformatter.GetOutput();  // write formatted display list
 
+	MergeConnectingVertexLists();
+
 	return sourceOutput;
 }
 
+void ZDisplayList::MergeConnectingVertexLists()
+{
+	if (vertices.size() > 0)
+	{
+		std::vector<std::pair<uint32_t, std::vector<ZVtx>>> vertexKeys(vertices.begin(),
+		                                                               vertices.end());
+		std::pair<uint32_t, std::vector<ZVtx>> lastItem = vertexKeys.at(0);
+
+		for (size_t i = 1; i < vertexKeys.size(); i++)
+		{
+			std::pair<uint32_t, std::vector<ZVtx>> curItem = vertexKeys[i];
+
+			size_t lastItemEnd = lastItem.first + (lastItem.second.size() * 16);
+			bool lastItemIntersects = lastItemEnd >= curItem.first;
+
+			if (lastItemIntersects)
+			{
+				int intersectedVtxStart = (lastItemEnd - curItem.first) / 16;
+
+				for (size_t j = intersectedVtxStart; j < curItem.second.size(); j++)
+					vertices[lastItem.first].push_back(curItem.second[j]);
+
+				vertices.erase(curItem.first);
+				vertexKeys.erase(vertexKeys.begin() + i);
+
+				lastItem.second = vertices[lastItem.first];
+
+				i--;
+			}
+			else
+				lastItem = curItem;
+		}
+	}
+}
+
 void ZDisplayList::TextureGenCheck()
 {
 	if (TextureGenCheck(lastTexWidth, lastTexHeight, lastTexAddr, lastTexSeg, lastTexFmt,
diff --git a/ZAPD/ZDisplayList.h b/ZAPD/ZDisplayList.h
index 9680831..c68713c 100644
--- a/ZAPD/ZDisplayList.h
+++ b/ZAPD/ZDisplayList.h
@@ -367,6 +367,9 @@ public:
 	std::string ProcessLegacy(const std::string& prefix);
 	std::string ProcessGfxDis(const std::string& prefix);
 
+	// Combines vertex lists from the vertices map which touch or intersect
+	void MergeConnectingVertexLists();
+
 	bool IsExternalResource() const override;
 	std::string GetExternalExtension() const override;
 	std::string GetSourceTypeName() const override;
-- 
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