From 62424215c1124cfb5a4ba2792ec105593636eb6d Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Sun, 9 Nov 2025 23:25:16 +0100
Subject: [PATCH] Fix crash due to missing asset reference inside
 `MeshAccelerationStructure`

---
 .../Tools/ModelTool/MeshAccelerationStructure.cpp   | 13 +++++++++++++
 .../Tools/ModelTool/MeshAccelerationStructure.h     |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.cpp b/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.cpp
index 4e551e445..11c449847 100644
--- a/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.cpp
+++ b/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.cpp
@@ -288,6 +288,15 @@ bool MeshAccelerationStructure::RayCastBVH(int32 node, const Ray& ray, Real& hit
     return hit;
 }
 
+MeshAccelerationStructure::~MeshAccelerationStructure()
+{
+    for (auto& e : _meshes)
+    {
+        if (e.Asset)
+            e.Asset->RemoveReference();
+    }
+}
+
 void MeshAccelerationStructure::Add(Model* model, int32 lodIndex)
 {
     PROFILE_CPU();
@@ -307,6 +316,8 @@ void MeshAccelerationStructure::Add(Model* model, int32 lodIndex)
         }
 
         auto& meshData = _meshes.AddOne();
+        meshData.Asset = model;
+        model->AddReference();
         if (model->IsVirtual())
         {
             meshData.Indices = mesh.GetTriangleCount() * 3;
@@ -350,6 +361,7 @@ void MeshAccelerationStructure::Add(const ModelData* modelData, int32 lodIndex,
         }
 
         auto& meshData = _meshes.AddOne();
+        meshData.Asset = nullptr;
         meshData.Indices = mesh->Indices.Count();
         meshData.Vertices = mesh->Positions.Count();
         if (copy)
@@ -370,6 +382,7 @@ void MeshAccelerationStructure::Add(const ModelData* modelData, int32 lodIndex,
 void MeshAccelerationStructure::Add(Float3* vb, int32 vertices, void* ib, int32 indices, bool use16BitIndex, bool copy)
 {
     auto& meshData = _meshes.AddOne();
+    meshData.Asset = nullptr;
     if (copy)
     {
         meshData.VertexBuffer.Copy((const byte*)vb, vertices * sizeof(Float3));
diff --git a/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.h b/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.h
index 7e158e742..c40ebc729 100644
--- a/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.h
+++ b/Source/Engine/Tools/ModelTool/MeshAccelerationStructure.h
@@ -20,6 +20,7 @@ class FLAXENGINE_API MeshAccelerationStructure
 private:
     struct Mesh
     {
+        Model* Asset;
         BytesContainer IndexBuffer, VertexBuffer;
         int32 Indices, Vertices;
         bool Use16BitIndexBuffer;
@@ -57,6 +58,8 @@ private:
     bool RayCastBVH(int32 node, const Ray& ray, Real& hitDistance, Vector3& hitNormal, Triangle& hitTriangle) const;
 
 public:
+    ~MeshAccelerationStructure();
+
     // Adds the model geometry for the build to the structure.
     void Add(Model* model, int32 lodIndex);