No, its not water colouring nor air brush technique. Its Piranesi by Informatix. Piranesi is a specialized ‘3D painting’ tool, allowing you to start with a simple rendering of a 3D model, and quickly develop it into high quality images ready for client presentations. This reminds me of SketchUp.
I’ve installed and tried it one year ago, and its a very big let down due to the interface that is not user friendly at all. The overall interface and button has this Windows 3.0 treatment, just like playing solitare in windows 98. Maybe they have improve the interface for the newly release version.