What you need to do is display two images one for each eye. Each image is a perspective view but taken from two slightly different viewpoints - about the distance of your eyes apart.
When viewed through polarising or more likely LCD Shutter glasses you get the illusion of 3D objects.
In this case each eye's view is presented on the screen alternately and a signal is sent to the glasses to become clear or opaque so that the correct image is seen in each eye.
For a passive system you have to use two projectors for the left and right eye images and make sure that they are perfectly aligned so the images overlap correctly. If you get it wrong you won't get a very good 3D effect.
In both cases you need to create two views of your model and render each one for each frame you display. I used to work in this area and a while back wrote a blog post which included an overview on how we did stereo systems.