I have to ask:
Why is it that you can save in COPY and T3D (whatever these are) but the engine itself seems to save .uasset files which cannot be imported or opened otherwise. What is the logic behind this?
You can’t import COPY or T3D files to the engine either.
You can import and export t3d files directly into and from the level. I don’t know where you see COPY and t3d as save options though.
If you right-click any asset in the asset browser you will be given T3D, COPY or if it’s a Texture TGA, if it’s a mesh FBX or (I think) Sound Cue exports WAV.
And the actor that I import (T3D) shows up nowhere.
T3D is a simple text format for a single object. It is the values of all the properties in the object and the references to other objects. It isn’t a deep export (i.e it will not export the properties of referenced objects or native c++ data). You can export them from the editor which is somewhat useful for copying properties between assets. However, the migrate content feature is now the best way to transfer between projects.
Export is not the same as save. Saving will create a .uasset file which can be referenced by your project and other objects in your project and contains all the data necessary to fully create that object in the engine. Example: exporting a static mesh as T3D will not export the raw triangles or rendering data but the .uasset file contains this information. T3D is somewhat legacy format for exporting but it is our copy/paste format in the editor (copy an actor and paste it into notepad to see what I mean). T3D is ideal for this because we don’t need to copy everything, just values unique to that object and references to other objects so when we paste a new actor can be created with the exact same properties. Another reason for using this format is to allow copy/paste between editor sessions. Duplicating in memory would make that more difficult.
.Copy is the same as .T3D just a different file extension. I will probably remove it to avoid confusion.
Hopefully this answers your questions.
Can I convert a .Copy to uasset file ?
Does ‘migrate’ support exporting & importing assets of different unreal version?