Outdoor background - shading part 3 (World environment and fog)

 There are mainly three elements for the world environment: sky dome, cloud, and fog.

For the sky dome, I chose one HDRI image that have a bright line of light on the horizon. Which can create a bloom effect at the top of the city’s wall. This HDRI image do not have a moon, so I can place my own moon mesh into the scene and have more control on the moon.

    Sky dome:

Moon:

The fog is separated into two parts: one is the fog on the grand hole, one is the fog of the world. Both are made with the volume shader in blender.

At first, I am a newbie to shading in blender. So, I just apply a volume shader to a cube and mounted it on the grand hole. It appeared as a simple light pillar.

I was satisfied with it at first. But later on, I found tutorials that teach me how to add more details to the fog and make it look better. 

Here are some process images of different editions of the fog:

Single layer of volume fog:

Adding in second layer of swirl volume and light particles with trails:

color adjustment:

Added third layer of dense volume fog inside the grand hole.

More contrast between the base volume and swirl volume.

Add a world volume (every object looks a bit dimmer).

World volume:

Base volume and swirl volume:

Dense volume filling up the hole:

Node tree of volume shader, which used noise texture and color ramp node mainly: