Finally, under Shape Instance, choose a new building by pressing the button under Particle Geometry Object, pressing H on the keyboard and selecting a new object from the list. I'll choose Rubble. Then play around with Scale and Variation once more until you're satisfied (Fig.28).
Repeat paragraph 2.6 until all buildings are scattered on the emitter. I chose 500 OfficeBuildings and 50 IntactSkyScrapers (Fig.29 & Fig.30).
Step 3: Finishing The Scene
As you probably don't want your ground texture to look like the distribution map, you need to hide the CityEmitter and use a plane with another texture instead. The easiest way is to select the CityEmitter, press Ctrl+V to duplicate it and choose Instance. Name the new plane Ground (Fig.31).
Then press H on the keyboard, choose CityEmitter and press OK. Right-click the plane and choose Hide Selection. You are now free to apply which ever texture you like to the Ground plane. I chose my very simple Rubble texture (Fig.32).
Now you just need to add some basic lighting and a moving camera and you're ready to proceed to rendering. For lighting I suggest a single direct light with a mental ray Shadow Map for shadows (Fig.33).
Step 4: Rendering
As mentioned above, we'll use mental ray for this tutorial, so the first thing to do is to enable the mental ray Renderer. Press F10 on the keyboard to open the Render Setup window and under the Common tab, scroll down to the bottom to the Assign Renderer section and press the button next to Production. Choose mental ray Renderer from the list. Next, scroll up again to set your resolution. In this example I'm using 640x360, but you are, of course, free to choose whatever resolution fits your needs. Next, set your frame range (0-100 in my example) and choose a place for saving your rendered files. I suggest creating a render folder as you'll end up with quite a few files. The file format we'll use is Targa Image File with the settings shown in Fig.34 & Fig.35.