I implement procedural terrain and road generation based on the paper of CityEngine. A previous version is here. In the final version, I rasterize every roads onto the map based on traditional rasterization method for triangles. Then, I extract valid pixels where no roads or sea overlap and separate them into independent groups (i.e. blocks) where streets emerge. Now, streets won't overlap in a block.
Final Result
Highway Blocks
Distincts
The entire map is divided into small grids where the program could set up buildings. Only those grids which have no intersection with roads or sea are valid. Then, the code randomly chooses some grids to set up procedural buildings.
Valid Grids with Roads
The method of procedural 3D building generation is introduced in the paper Real-time Procedural Generation of 'Pseudo Infinite' Cities. The basic algorithm is to procedurally generate a series of polygons when extruding from ceiling to floor along with union operation and random bias around base point.
In my project, the appearance of building varies from areas with high population density to low. In areas of lower density, buildings are more like houses. They are almost cuboid, short and with fewer layers or floors. By contrast, in areas of higher denstiy, buildings are more like skyscrapers with more faces and floors, and considerably taller than those houses. In the transition areas, there are more offices with a mixed appearance. Moreover, lower density of population, lower density of buildings, and vice versa.
Textures varies from high density to low as well. In this project, three different types of building textures are simply applied on correspounding building geometries.
Houses
Offices
Skyscrapers
Distribution with Population
Use shadow map to generate shadows for the scene. Only direction light from the sun casts shadows. A bluish indirection light is simply from up to down to color the shadow.
Use FBM Perlin noise to generate a procedural flowing cloud.
- Real-time Procedural Generation of 'Pseudo Infinite' Cities
- CityEngine
- IQ's article on artistic lighting
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