City-Generator

This project is based on Yocto/GL Library, introducing a random city generator. Features included:

• Random building and street generation
• Possibility to choose:
  • City size
  • Maximum number of floor of the buildings
  • How many times the streets have to be forked
  • The chance to place a building
  • The chance to place trees
  • The urbanization (explained later)
  • Day or Sunset mode
• Saving the scene to Obj file

This generator creates a bidimensional matrix and populates it as follows. At the beginning roads are created by using a sort of random walk algorithm. The algorithm "walks" in a direction and for each step it has a certain probaility to fork in a perpendicular direction (or double fork). If it forks, it will "walk" in the new direction and the fork probability will be halved. When the road reaches the border of the matrix or some other critical cases (such as a street parallel to the one near it) it will stop and the algorithm will continue from the point where it forked. The result is a random road network that contains crossroads and can be more or less complex depending on the input of fork-probability. After that we will have a matrix that contains the roads in order to let us place buildings and trees. The algorithm will then place buildings near the roads with the input of building-creation-probability, otherwise will place trees with the input of tree-creation-probability and will check the crossroads or the end of a road placing the right model.

When the alghoritm have to build. First of all checks for how much free space it has near the actual location (so how many free spaces in the matrix on x an y axes) to find out what can be the maximum leght of the Building. Then it builds a large construction on the free spots.

In this way the buildings are recursively generated. For each step a random floor, base or roof will be choosen, managing the compatibility between the models and the position of them.

The urbanization lets the user choose how the city will look like and if it will have only big buildings or small houses. Starting from the center of the city to the borders there will be more or less high buildings and trees depending on the value of the input of urbanization.

The sunset mode is a special setting that will create a suggestive atmosphere making your generated-city look really cool.

Outputs and generation parameters:

./bin/city_generator -size 40 -sc 40 -bc 70 -u 80 -s

./bin/city_generator -size 40 -sc 40 -bc 70 -u 80

./bin/city_generator -size 40 -sc 40 -tc 70 -bc 70 -u 80

./bin/city_generator -size 40 -sc 60 -bc 70 -u 0

./bin/city_generator -size 40 -sc 60 -bc 70 -u 100

You can find more examples in images folder.

Building and Running:

Build:

./build.sh

Run:

./bin/city_generator

For the prerequisites look at Yocto/GL

Parameters:

• -size int to specify the size of the city default = 30

• -m int to specify the minimum number of floors of the buildings of the city default = 1

• -M int to specify the maximum number of floors of the buildings of the city default = 5

• -sc int to specify the probability for the roads to fork default = 30

• -bc int to specify the probability for a building to be placed default = 50

• -tc int to specify the probability for a tree to be placed default = 30

• -u int to specify the urbanization level of the city default = 75

• -s to activate the sunset mode

• -o string to specify the output filename where the scene will be saved default = "scene_out.obj"

Example:

./bin/city_generator -size 40 -tc 30 -sc 60 -bc 50 -u 70 -o generated_city.obj

Street generation example:

The generation of the streets can be controlled by adjusting the -sc parameter. These are some outputs:

with high split chance

with 0 as split chance

with default as split chance

Authors

Andrei Stefan Bejgu

Credits

Fabio Pellacini for the Yocto/GL library.