Massive file size increase after joining objects

Hi, I have a blend file with dozens of detailed objects whose size is 123MB. I have done the following:

  • created groups and assigned various objects to groups
  • I have joined objects into a fewer set of objects (about 6) using CTRL+J

After the join operation, Blender started to become very slow. When saving the file, it is now 2.78GB! I have tried to create a new blank file and append only the meshes joined previously, but the new file is also 2.78GB and blender acting really slow. What happened and how can I get out of this mess? I am using Blender 2.69 on OS X. I am sorry I cannot share the file as it contains copyrighted material.

No idea, but did the joined objects had different modifiers on them instead of all having the same ?

There are no modifiers. Ok I have narrowed down the problem. It comes from a specific joint of a set of detailed screws. The object alone amounts to 663782 vertices, 517500 faces and 1319340 triangles. When saved alone, it takes 2.5GB. Initially the screws were in smaller sets of like 12 screws and the file was much smaller. For some reason, when joining them all into a single object, the file is huge.

Maybe screws were instances and when joining together Blender must store all new data from screws.

@TynkaTopi: so you mean the mesh of the screw was defined only once and each screw was an instance of this mesh? I didn’t know we could do this in Blender but this is good to know. Yes maybe is the reason why. In the meantime what I did is instead of creating a single object with all the screws, I created several objects with sets of screws. This way the scene is manageable. However if there is a single mesh with several instances, it would be good to preserve this organization. Is there a way to check this is the case?

Shift+L > Object data, selects all instances. And in Properties panel > Object Data shows how many instances.


Thanks TynkaTopi. After checking on my scenes, there are no multiple instances of the same mesh. Anyway, I mitigated the problem by creating multiple objects being sets of screws instead of having a single object with all the screws.