From 8ad1705e7546605203a468be9b41011a072b8b69 Mon Sep 17 00:00:00 2001
From: SashaRX <SashaRX@ya.ru>
Date: Thu, 6 Aug 2026 13:45:41 +0200
Subject: [PATCH] Avoid cumulative transform baking on shared meshes

---
 Editor/Tools/LightmapTransferTool.cs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Editor/Tools/LightmapTransferTool.cs b/Editor/Tools/LightmapTransferTool.cs
index 4e680229..c838784b 100644
--- a/Editor/Tools/LightmapTransferTool.cs
+++ b/Editor/Tools/LightmapTransferTool.cs
@@ -3907,7 +3907,15 @@ static Dictionary<string, string> NormalizeExportHierarchy(GameObject root)
                 var mesh = childMf.sharedMesh;
                 if (!mesh.isReadable) continue;
 
-                BakeTransformIntoMesh(mesh, t);
+                // A cloned FBX hierarchy can contain several nodes that instance
+                // the same Mesh. Baking into sharedMesh directly would apply each
+                // node's transform cumulatively to that one object. Give every
+                // transformed node its own copy before mutating the vertex data.
+                var bakedMesh = UnityEngine.Object.Instantiate(mesh);
+                bakedMesh.name = mesh.name;
+                childMf.sharedMesh = bakedMesh;
+
+                BakeTransformIntoMesh(bakedMesh, t);
 
                 // Reset transform to identity
                 t.localPosition = Vector3.zero;