Called whenever an engine object is being modified. Use this to set the reinitialize assets flag. For example when a skeletal mesh or anim sequence change (being modified or reimported), we should set the bNeedsAssetReinit member to true, to trigger the actor components and UI etc to be reinitialized. The default implementation of this method will check for changes in the skeletal mesh and training and test anim sequence. If you want to check more things (your target mesh), you need to check for that.