Well, there is a very obvious limit to the fidelity of your simulation if presence is your goal: human perception. You don't need to crank up any details beyond

Well, there is a very obvious limit to the fidelity of your simulation if presence is your goal: human perception. You don't need to crank up any details beyond what you can possibly perceive when using the simulation. Gravitational space distortions are the least worrisome effects in that regard. Light diffraction and polarization play a much larger role in our environment, although not often and if it happens, the untrained eye tends not to notice. I am talking about things like birefringent materials (quartz crystals) and diffraction effects like light reflected off of a CD or shining through a thin piece of cloth. You can repeat the same process with each kind of sensory input a human can perceive and get to pretty hard limits on the requirements to get "perfect" realism. Human perception hasn't been researched in enough detail yet to give accurate bounds in all cases, but this is actively being worked on. The known bounds are mostly really conservative ones.