Hello, I know this thread is old but I'll respond anyway.

The kind of visualization you're talking about requires two things: 1) developing your visualization skills and 2) snapping yourself into an altered state of consciousness.

Let me explain what I mean by this. When someone has a visual hallucination, whether it's because they're on drugs or they are having a schizophrenic hallucination, they are actually also in an altered state of consciousness. In order to see something that's not there requires one to be somewhat in an altered state. To get an idea of what this feels like, and you've probably done this many times, think back to a time when you were in school and instead of listening to the teacher you start thinking about something, and then you start being so much into your thoughts that you're actually daydreaming, seeing what you're imagining, and almost like being transported to a different place, experiencing your thoughts, until something snaps you out of it.

Now I know what you are looking for is to be able to actually see visually without being in an altered state and thought I'm not one to say anything is impossible, I would say that some change of consciousness must take place in order for the vision to crystalize and look real. You can practice building these skills for both at the same time:

Practice visualizing a simple object, but instead of just visualizing it, also feel it, smell it, hear it, hold it, throw it, get a 'feeling/knowing' from it. Using all your senses instead of just your visual sense will pull you into an altered state much quicker. Start with simple objects, then move on to more complex objects, cups, cars, clothes, a person's face.

As someone wrote earlier, in the beginning it will only be in your imagination with microsecond flashes of it visually where you won't even be sure if you saw anything. But eventually it will become more and more solid, the microflashes lasting longer and longer.

What you're doing by practicing visualizations like this is creating connections in your brain to be able to visualize things vividly. Since it's not something we humans practice because we don't need it, we have never developed it and the brain connections are not there yet - but they will be with regular exercise, I promise. Look at it this way: people who were blind all their lives because of severe cataracts were never able to develop the brain connections to see. Once they had cataract surgery you'd think they'd be able to see perfectly, but that's not the case at all. It will take months for the person to develop the ability to do a simple task like distinguishing between a circle and a square. But will it be worth the effort? Absolutely. So, yes, it will take a long time to develop this ability, maybe 2 years of daily practice, one if you're lucky.

For those in here who gave the questioner a hard time about the question, I will tell you what an ability like this can be used for. Once you develop this level of skill (or even a more basic level of being able to hold in the mind's eye a picture) you will be able to receive psychic impressions in the form of visions. While you will still have to learn to how to interpret these, by practicing the other senses as well (hearing, touch, feeling/knowing, smell) you will be a long way toward becoming psychic. I know it sounds crazy but it will happen. We all have the potential, we just have to develop it. One day, you'll be thinking, where did I put my keys, and you will see clearly, in a visual form, where your key was lost - and you'll understand how this is the beginning of a much more powerful way of knowing.

One of the best books I can recommend on this subject, and all psychic/intention abilities is: Initiation Into Hermetics by Franz Bardon. It's a complete manual on developing your abilities, with step by step directions.