Duplicating Models as References

From Trinity Reign Wiki

When you duplicate a model using Blender and you plan on not changing the model at all (for example, street lights lining the streets), make sure you duplicate it as a reference to the original. The reason for this is because if you don't, you'll end up with many duplicates of the same model being exported separately as opposed to one model being exported. This will in turn hurt the performance of the game and become a real nightmare to deal with. In order to duplicate a model as a reference, simply press alt+d.