Add MeshReference to ModelInstanceActor for easy mesh referencing and its data access interface

Source/Engine/Level/Actors/AnimatedModel.cpp

@@ -945,6 +945,18 @@ bool AnimatedModel::IntersectsEntry(const Ray& ray, Real& distance, Vector3& nor
     return result;
 }
 
+bool AnimatedModel::GetMeshData(const MeshReference& mesh, MeshBufferType type, BytesContainer& result, int32& count) const
+{
+    count = 0;
+    if (mesh.LODIndex < 0 || mesh.MeshIndex < 0)
+        return true;
+    const auto model = SkinnedModel.Get();
+    if (!model || model->WaitForLoaded())
+        return true;
+    auto& lod = model->LODs[Math::Min(mesh.LODIndex, model->LODs.Count() - 1)];
+    return lod.Meshes[Math::Min(mesh.MeshIndex, lod.Meshes.Count() - 1)].DownloadDataCPU(type, result, count);
+}
+
 void AnimatedModel::OnDeleteObject()
 {
     // Ensure this object is no longer referenced for anim update

Source/Engine/Level/Actors/AnimatedModel.h

@@ -374,6 +374,7 @@ public:
     void Deserialize(DeserializeStream& stream, ISerializeModifier* modifier) override;
     bool IntersectsEntry(int32 entryIndex, const Ray& ray, Real& distance, Vector3& normal) override;
     bool IntersectsEntry(const Ray& ray, Real& distance, Vector3& normal, int32& entryIndex) override;
+    bool GetMeshData(const MeshReference& mesh, MeshBufferType type, BytesContainer& result, int32& count) const override;
     void OnDeleteObject() override;
 
 protected:

Source/Engine/Level/Actors/ModelInstanceActor.h

@@ -12,6 +12,23 @@
 API_CLASS(Abstract) class FLAXENGINE_API ModelInstanceActor : public Actor
 {
     DECLARE_SCENE_OBJECT_ABSTRACT(ModelInstanceActor);
+
+    /// <summary>
+    /// Utility container to reference a single mesh within <see cref="ModelInstanceActor"/>.
+    /// </summary>
+    API_STRUCT(NoDefault) struct MeshReference : ISerializable
+    {
+        DECLARE_SCRIPTING_TYPE_MINIMAL(MeshReference);
+        API_AUTO_SERIALIZATION();
+
+        // Owning actor.
+        API_FIELD() ScriptingObjectReference<ModelInstanceActor> Actor;
+        // Index of the LOD (Level Of Detail).
+        API_FIELD() int32 LODIndex = 0;
+        // Index of the mesh (within the LOD).
+        API_FIELD() int32 MeshIndex = 0;
+    };
+
 protected:
     int32 _sceneRenderingKey = -1; // Uses SceneRendering::DrawCategory::SceneDrawAsync
 
@@ -24,8 +41,8 @@ public:
     /// <summary>
     /// Gets the model entries collection. Each entry contains data how to render meshes using this entry (transformation, material, shadows casting, etc.).
     /// </summary>
-    API_PROPERTY(Attributes="Serialize, EditorOrder(1000), EditorDisplay(\"Entries\", EditorDisplayAttribute.InlineStyle), Collection(CanReorderItems = false, NotNullItems = true, ReadOnly = true, Spacing = 10)")
-    FORCE_INLINE Array<ModelInstanceEntry> GetEntries() const
+    API_PROPERTY(Attributes="Serialize, EditorOrder(1000), EditorDisplay(\"Entries\", EditorDisplayAttribute.InlineStyle), Collection(CanReorderItems=false, NotNullItems=true, ReadOnly=true, Spacing=10)")
+    FORCE_INLINE const Array<ModelInstanceEntry>& GetEntries() const
     {
         return Entries;
     }
@@ -80,6 +97,19 @@ public:
     {
         return false;
     }
+    
+    /// <summary>
+    /// Extracts mesh buffer data from CPU. Might be cached internally (eg. by Model/SkinnedModel).
+    /// </summary>
+    /// <param name="mesh">Mesh reference.</param>
+    /// <param name="type">Buffer type</param>
+    /// <param name="result">The result data</param>
+    /// <param name="count">The amount of items inside the result buffer.</param>
+    /// <returns>True if failed, otherwise false</returns>
+    virtual bool GetMeshData(const MeshReference& mesh, MeshBufferType type, BytesContainer& result, int32& count) const
+    {
+        return true;
+    }
 
 protected:
     virtual void WaitForModelLoad();

Source/Engine/Level/Actors/StaticModel.cpp

@@ -588,6 +588,18 @@ bool StaticModel::IntersectsEntry(const Ray& ray, Real& distance, Vector3& norma
     return result;
 }
 
+bool StaticModel::GetMeshData(const MeshReference& mesh, MeshBufferType type, BytesContainer& result, int32& count) const
+{
+    count = 0;
+    if (mesh.LODIndex < 0 || mesh.MeshIndex < 0)
+        return true;
+    const auto model = Model.Get();
+    if (!model || model->WaitForLoaded())
+        return true;
+    auto& lod = model->LODs[Math::Min(mesh.LODIndex, model->LODs.Count() - 1)];
+    return lod.Meshes[Math::Min(mesh.MeshIndex, lod.Meshes.Count() - 1)].DownloadDataCPU(type, result, count);
+}
+
 void StaticModel::OnTransformChanged()
 {
     // Base

Source/Engine/Level/Actors/StaticModel.h

@@ -168,6 +168,7 @@ public:
     void Deserialize(DeserializeStream& stream, ISerializeModifier* modifier) override;
     bool IntersectsEntry(int32 entryIndex, const Ray& ray, Real& distance, Vector3& normal) override;
     bool IntersectsEntry(const Ray& ray, Real& distance, Vector3& normal, int32& entryIndex) override;
+    bool GetMeshData(const MeshReference& mesh, MeshBufferType type, BytesContainer& result, int32& count) const override;
 
 protected:
     // [ModelInstanceActor]