From 228b6181fcaa4f643e77273597df60b5bb0a5fc3 Mon Sep 17 00:00:00 2001
From: envision3d <envision3d@envision3d.org>
Date: Sat, 19 Sep 2026 12:49:16 -0500
Subject: [PATCH] MaterialInstance: save virtual assets via temp chunk

---
 .../Engine/Content/Assets/MaterialInstance.cpp | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/Source/Engine/Content/Assets/MaterialInstance.cpp b/Source/Engine/Content/Assets/MaterialInstance.cpp
index 61d5c5b62..d0e7bf77c 100644
--- a/Source/Engine/Content/Assets/MaterialInstance.cpp
+++ b/Source/Engine/Content/Assets/MaterialInstance.cpp
@@ -332,7 +332,18 @@ bool MaterialInstance::Save(const StringView& path)
         // Save parameters
         Params.Save(&stream);
     }
-    SetChunk(0, ToSpan(stream));
+    // Virtual assets don't own a storage container, so SetChunk/GetOrCreateChunk are a no-op for them.
+    // Wire a temporary chunk into the header for the duration of the save (mirrors ModelBase::Save).
+    FlaxChunk tmpChunk;
+    if (IsVirtual())
+    {
+        tmpChunk.Data.Copy(ToSpan(stream));
+        _header.Chunks[0] = &tmpChunk;
+    }
+    else
+    {
+        SetChunk(0, ToSpan(stream));
+    }
 
     // Setup asset data
     AssetInitData data;
@@ -340,6 +351,11 @@ bool MaterialInstance::Save(const StringView& path)
 
     // Save data
     const bool saveResult = path.HasChars() ? SaveAsset(path, data) : SaveAsset(data, true);
+    if (IsVirtual())
+    {
+        // Release the temporary chunk reference (points to stack memory)
+        _header.Chunks[0] = nullptr;
+    }
     if (saveResult)
     {
         LOG(Error, "Cannot save \'{0}\'", ToString());