How would we manage, if we could not visualise three-dimensional objects from flat two-dimensional diagrams? An amazing feat our brain performs. What role does pre-determined programming play in this? That is related to how the sun shines on us.
Someone who is hallucinating will see things, whole scenes and events which are not actually there, and experience them as real.How can this be? Because you see what you expect, unless it is corrected by your perceptions. Which is where things can go wrong.
Are you sure you see the reality out there? That is the question. The brain does not receive an image like a camera does. The brain is not a passive processor. What you see is constructed in the brain. How do you see with your brain?