When destroying an Actor with a Procedural Mesh Component; that is stored in an Array Variable, the memory for that Actor's Procedural Mesh Component is not cleared, leading to a Memory Leak. However, If you make the actor into a Single Variable and destroy it, that Procedural Mesh's memory is properly cleared by Unreal's Garbage Collection.

Steps to Reproduce

NOTE: See attachment  ""  for simplified project source replication. 


Open Unreal Engine 4.20-> Create Third Person Blueprint Template.

Creating Procedural Mesh Actor

  1. Inside of Content Folder-> Create a new Blueprint Actor class. "TestActor"
  2. Inside of Blueprint Actor-> Add Component-> Procedural Mesh
  3. Inside of Blueprint Actor->Construction Script-> Create new local variable
  4. Name local Variable "Vertices" and choose Vector Array for Variable Type->Compile.
  5. Populate the Array with 8 elements, set the vector coordinates as shown in attached file: ProceduralMeshActor.png.
  6. Create a local Variable "Triangles", and choose Integer Array for Variable Type->Compile.
  7. Populate the Array with 36 elements, set default values as shown in attached file: ProceduralMeshActor.png

Creating a new Blueprint Player Controller

  1. Create a new Blueprint Player Controller
  2. Inside of Player Controller Blueprint-> Create a new variable called "Chunk Test Array" of type "TestActor", and make it an Array->Compile.
  3. Inside of Player Controller Blueprint->Create a new variable of type integer, named "MeshIDs"->Compile.
  4. Drag off of the event tick node of the Player Controller event graph, and implement the following. (see attached file: PlayerControllerEventGraph.PNG) 

Playing in Editor

  1. Create a new Blueprint Game Mode.
  2. Change Player Controller class to PlayerController Blueprint.
  3. Change Default pawn class to ThirdPersonCharacter.
  4. Go to Project settings->Maps&Modes-> Choose Gamemode_Bp for Default Game mode.
  5. Open up Windows Task Manager to monitor memory usage.
  6. Play in Editor

Expected: The Memory used by the Procedural Mesh Component is cleared when the Actor is destroyed.

Result: The memory usage of Unreal Engine will keeping going up while you play until your computer runs out of memory and the game/editor crashes. The actor is successfully destroyed, yet the memory taken by the mesh geometry is still remaining.

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Cannot Reproduce
Affects Versions4.194.204.21
Target Fix4.22
CreatedOct 15, 2018
ResolvedDec 11, 2018
UpdatedDec 12, 2018