From aaaca914a62177276691a63cbf6cc33a0c954185 Mon Sep 17 00:00:00 2001
From: Kawe Mazidjatari <48657826+Mauler125@users.noreply.github.com>
Date: Mon, 8 Jul 2024 12:29:44 +0200
Subject: [PATCH] Recast: union poly groups connected through off-mesh
 connections

Poly groups connected though off-mesh connections should be unioned. Confirmed working during in-editor tests.
---
 .../Detour/Source/DetourNavMeshBuilder.cpp    | 45 ++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/thirdparty/recast/Detour/Source/DetourNavMeshBuilder.cpp b/src/thirdparty/recast/Detour/Source/DetourNavMeshBuilder.cpp
index 145763fe..8c2b6a88 100644
--- a/src/thirdparty/recast/Detour/Source/DetourNavMeshBuilder.cpp
+++ b/src/thirdparty/recast/Detour/Source/DetourNavMeshBuilder.cpp
@@ -381,6 +381,49 @@ bool dtCreateDisjointPolyGroups(dtNavMesh* nav, dtDisjointSet& disjoint)
 		}
 	}
 
+	// Third pass to handle off-mesh connections.
+	// note(amos): this has to happen after the first and second pass as these
+	// are for grouping directly connected polygons together, else groups linked
+	// through off-mesh connections will be merged into a single group!
+	// 
+	// todo(amos): should off-mesh links be marked reachable for all traverse
+	// anim types? Research needed on Titanfall 2. For now, mark connected
+	// poly groups with off-mesh connections reachable.
+	for (int i = 0; i < nav->getMaxTiles(); ++i)
+	{
+		dtMeshTile* tile = nav->getTile(i);
+		if (!tile || !tile->header || !tile->dataSize) continue;
+		const int pcount = tile->header->polyCount;
+		for (int j = 0; j < pcount; j++)
+		{
+			dtPoly& poly = tile->polys[j];
+
+			if (poly.getType() != DT_POLYTYPE_OFFMESH_CONNECTION)
+				continue;
+
+			unsigned int plink = poly.firstLink;
+			unsigned short firstGroupId = DT_NULL_POLY_GROUP;
+
+			while (plink != DT_NULL_LINK)
+			{
+				const dtLink l = tile->links[plink];
+				const dtMeshTile* t;
+				const dtPoly* p;
+				nav->getTileAndPolyByRefUnsafe(l.ref, &t, &p);
+
+				if (p->groupId != DT_NULL_POLY_GROUP)
+				{
+					if (firstGroupId == DT_NULL_POLY_GROUP)
+						firstGroupId = p->groupId;
+					else
+						disjoint.setUnion(firstGroupId, p->groupId);
+				}
+
+				plink = l.next;
+			}
+		}
+	}
+
 	// Gather all unique polygroups and map them to a contiguous range.
 	std::map<unsigned short, unsigned short> groupMap;
 	unsigned short numPolyGroups = DT_FIRST_USABLE_POLY_GROUP; // Anything <= DT_STRAY_POLY_GROUP is reserved!
@@ -398,7 +441,7 @@ bool dtCreateDisjointPolyGroups(dtNavMesh* nav, dtDisjointSet& disjoint)
 		}
 	}
 
-	// Third pass to apply the new mapping to all polys.
+	// Fourth pass to apply the new mapping to all polys.
 	for (int i = 0; i < nav->getMaxTiles(); ++i)
 	{
 		dtMeshTile* tile = nav->getTile(i);