1.For the creation of cities I create first a set of specific buildings. Create from 5 to 10 different structures (Fig. 1).
Than combined some of these structures to create other buildings.
It is always good to create basic structure and combined them to create more complex one.
2. Create a basic plane with a sufficient number of subdivisions and convert it to editable poly.
Select some range of polygons and extrude them to create channels
(you can create different up and down levels on your plane by extrude upper and lower other poly regions).
Than duplicate multiple times the plane and resize some of the duplication to create various basement with different size of polygons.
3. To fill the city there are three main techniques that you can use.
First the scatter modifier and applying these scatter to some simple buildings.
Secondly, the particle system with very buildings model as particle.
A third option is to use the free modifier “Greeble”
( you can download it freely here http://max.klanky.com/plugins.htm).
For this city I have choose the greeble modifier option.
Select polygons from the basement plane, inset them to leave space around the greeble buildings,
detach as clone the polygons (Fig. 4).
Apply the greeble modifier on these detached polygons.
By doing this process multiple times with different parameters size in the greeble modifier and
different region selection, you obtain my mass building effect.
Now you can place the buildings that you have created in step 1.
Try to spread them in a kind of coherent way by looking some city references.
You can create spaceship to have something that look like birds flying gently.
The modeling of them could be simple as this one.
Now that all elements are done, you have to combined them together to create the composition.
You can use the ⅓ composition rule and re-center the image
For the lighting you can use three lights, a front, a back and a left spot.
The front light is the main one. To create some more realistic lighting I have put a noise map on my main spot.
That give many different lighting level on the city which is like clouds are in the sky.
For the textures themselves, I have choose one multi material using same kind of patterns to make the city more uniform.
I have use only three passes for this scene, Ambient Occlusion, ZDepth and normal.
These passes will help me in photoshop to create my final image
Make a render save it in tga format to have the alpha channel.
In photoshop open the tga render, add a layer with the occlusion pass and another with zdepth pass.
I have inverted the zdepth pass and use screen fusion. For the occlusion layer I have used the multiply fusion.
After I have work with the backgrounds city to create more depth and add the 2D sky and planet images to finalise the composition.