The workflow to export static meshes from blender to unreal is:
blender:
-Set your scene scale to 0.01
-Finish your model in blender and create 2 UV sets, first one will be used for texturing and the second one will be used by UnrealEngine for baking light maps.
-If you have models that shares the same data block and should be instanced in unreal select one of those meshes and prefix it’s name with “SM_REF_”
and Ctrl+A and select “Rotation & Scale” to zero out this mesh rotation and scale (this is necessary for instanced meshes to be exported correctly).
For example if you have a 3 meshes “door1”, “door2” and “door3” and the all share the same data block, select one of them, say “door 1” and rename it “SM_REF_door1” or “SM_REF_AnyName”
and hit Ctrl+A and select “Rotation & Scale” to zero out it’s rotation and scale.
-Now if you want to preserve instanced meshes in unreal create a collision meshes for this mesh only using the usual unreal collision mesh prefix for example “UCX_SM_REF_door1_01”, “UCX_SM_REF_door1_02”…etc
otherwise create a collision mesh for every model.
-From blender “Select” menu select “Select All By Type” -> “Mesh”. to select all mesh objects.
-From blender “File” menu select “Export” -> “UnrealEngine (.fbx)”
-In the “Assets Path” export option write the relative path to your Unreal project mesh directory, default game directory in unreal is “/Game”.
This will export a separate fbx file for each object selected. every fbx file contains one object positioned in world origin (0,0,0) with all it’s collision meshes.
If “Preserve Instances” option is checked the addon will search for an object with the prefix “SM_REF_” and export that object only so when importing to unreal all objects will reference that mesh.
UnrealEngine:
-Right click in the “Content Browser” window and select “Import In <FolderName>”.
-Select all fbx files exported from blender.
-In the import dialog deselect “Merge Objects” and “Generate Lightmap UV” options. (this assumes that you have created 2 UV sets in blender)
-Click on “Import All”
-After import go to “Edit” menu and select “Paste” (This assumes that you’ve selected “Serialize To Clipboard” option when exporting from blender)
this will paste all the meshes in it’s original location as it was in blender, also all instanced meshes should be created and should reference the same static mesh
exported from blender. for example “door2” and “door3” will be created and their static mesh will be “SM_REF_door1”.
Also all objects should have their origin in the same position as it was in blender.
-If you modify some object location, rotation or scale in blender and you want to update it’s transform in unreal. select that object and export again from blender,
but this time uncheck “Export” and select “Serialize To Clipboard” this will only write the object to clipboard and not export it again to save time.
Then go to unreal and delete that object from the PERSPECTIVE VIEW NOT FROM CONTENT BROWSER and again from the “Edit” menu select “paste” to paste it again.
have fun.