Step
- Create the river layout with spline tool and adjust the layout with your needs

- Drag the terrain HDA into the map

- Define the area for the city with a box, and this area will be generated flatly

- Set the Houdini Inputs as World Outliner Input and feed the spline tool and the box to the HDA
- Caution: each modification might take 20 - 60 seconds to update
- Changeable parameters:

- Refine the mesh & Bake the terrain

- Rescale the baked static mesh (1000 for this project) and apply textures
