Depth of Field is a feature that uses blurring techniques to create in focus and out of focus objects. It gets used in cinematography, photography, as well as computer animation as its aesthetically pleasing because it’s kind of how we see things in real life.
In regards to Trainz: A New Era, depth of field is an effect with two purposes. The first is to reinforce the illusion of depth and further the 3-D feel in the scene you’re viewing. It’s very easy for computers to make sure that every item in a scene, no matter how near or far it’s supposed to be, is perfectly in focus. Since this isn’t how we naturally view the world, it can seem foreign to our eyes and can disturb the illusion or immersion of the simulated world.
When we look at a scene, we don’t see everything in sharp focus at once. Our eyes have a very narrow point of sharp focus, just a couple of degrees, but they dart about very quickly when we observe a scene, painting in the detail as they go. In this way, Depth of Field allows us to increase the level of realism experienced.
The second reason for using depth of field is to focus your attention on the items which are more important. It doesn’t make sense for trees off in the distance to always be in focus. Depth of Field also allows low resolution textures to be used for distance/background objects, which gives us numerous more options and benefits when creating new routes and sessions.
In the above image, you can see the comparison between non-active/active Depth of Field post processing.