I have made an arcviz scene with different objects that are complex (level of detail pretty good and I prepared render but there is a problem: the cuda memory (3 gb) is not enough for the scene. I am trying to solve the thing without actually losing precision or realism, but the problem still persist (I tried rendering layers separated but there is still the problem of the objects being connected (shadows or others) one another, so if i render one, it seems out of place because it hsn't the shadow or reflexed of other objects of the scene. Do you have any suggestion?
I'm guessing the rug is causing the problem, due to the number of hair particles. If that is the cause, try changing the particle settings or use geometry instead of the hair strands as strand.
Or invest in a better graphics cards, Gtx 1060 with 6 gig of memory works great for my projects.
When it comes to complex scenes with particle systems, you might invest some time into learning compositing.
You can separate your scene's problematic elements into Render Layers, render them individually and then using Blender's built-in compositor to "glue" the layers back together.
For a quick explanation on how to use the various layers in Blender, check out Gandalf's explanation here:
Blenderguru has a good tutorial about splitting up a scene for rendering and then using the compositor to combine them again, which you can find here: