Jiewen Wang

Interactive Simulation of 3D City

Since 1960s, the concept that a city can be encased in a single "megastructure" building was popularized by architects and architectural groups including the Metabolist Movement, Archigram, Constant Nieuwenhuys and Yona Friedman. The ever-expanding urbanization and ever-increasing population demand much more space and resources that traditional cities can offer. Therefore, architects conceive of megastructure in which many individual units, houses and city infrastructures build on a huge structure. It occupies less ground area and supports high density of population. A city holding tens of thousands of people can be composed of one or several megastructures. Some radical proposals following this trend are totally subversive to modern way of living, such as Peter Cook's Plug-in City where citizens with full autonomy on urban planning can plug their modular houses into anywhere in megastructure city, and Kenzo Tange's Tokyo Bay Plan where entire city builds on floating structures on the sea.

Admittedly, most megastructure proposals are utopian concepts. They are never built. They are never meant to be built in the first place. They are thought experiments that push the boundary of architecture. They serve to address urban design issues such as sustainable living, geopolitical rights and transportation effectivity. If future humans are to live in ultrahigh density cities of whatever forms, some problems will have been addressed by current megastructure designs. As Karl Mannheim once said, that utopias of today may become realities of tomorrow.

Dr. Yi’an Lei, professor at Peking University, proposed a new form of megastructure – 3D city. In his book Next Revolution, he investigated the possibilities of building a cube-like city featuring extensive vertical transportation and the revolution it could bring about to our society. Population density could reach hundreds of thousands people per square kilometer, which exceeds current 2D cities by an order of magnitude.

This project investigates a simple form of 3D city. It follows the basic principle of megastructure, that the city is built upon a basic structure with changeable, modular structural components. The skeleton of 3D city consists of several platforms layered vertically, each can be as large as one square kilometer. The vertical distance of neighboring platforms may be ~40 meters which is 10 floor height. There are high-capacity elevators passing through platforms to provide fast vertical transport. Each platform is firm enough to bear low to midrise buildings, plazas, parks, water and energy infrastructures, just as an area of ground space in traditional 2-dimensional city does. We change the concept of ground into multiple vertically-layered platforms, upon which smaller buildings and structures can be built. Therefore, the space occupied by the city is totally 3D.

We developed an interactive simulator in Unity that allows users to plan residential and commercial areas in a 3D city, build elevators for vertical transportation and simulate traffic flow in real-time.


#ComputationalDesign #UrbanSimulation #UtopianArchitecture

  • Concept rendering of a 3D city using Vray with Sketchup. Megastructure platforms are built on top of high-density skyscrapers, providing extra ground space for residential houses, vertical parks and plazas. It shows a perpetual state of constructing and evolving. The unfinished construction on the top level will not hinder the operation of city below.

  • Above is a schematic picture of a 3D city in the simplest form, which consists of ten square platforms, each one of which is 1km long and 1km wide.

  • There can be many different types of 3D city. Here are another two types. The first one has interlaced platforms where connectivity is improved. The second one has small platforms stacked on large platforms, so that citizens living in each one of these stacks have more autonomy and privacy. The simulator works on all of these three types.

  • Is vertical transportation efficient enough to fulfill citizens’ needs? Will there be traffic jams at elevators during rush hours? How is traffic efficiency affected by different scenarios of city planning? To answer these questions, we use Unity game engine to build an interactive simulation program that allows users to design and modify the 3D city and see its impacts on traffic efficiency. Agent-based model and Monte-Carlo method are implemented to simulate traffic flows.

  • The model has three components: a synthetic urban population, grid-based buildings and traffic graph. There are two types of buildings: residential units where people live and commercial buildings where people work and randomly visit. Each citizen is assigned a place to live and a place to work in. At the beginning of day, the program generates a schedule for each citizen. As time goes by, the person visits a series of places and finally return home. The traffic graph is an abstraction of platforms connected with elevators. Shortest path algorithm is implemented to find a route travelling through elevators. The program is then able to collect everyone’s travel time data at each time of the day.

  • User can navigate in the vertical city, add buildings and elevators. The program can also randomly generate them. When simulation begins, average travel time of citizens and waiting time of elevators are automatically updated in the graph. Status of the city can be save to disk. Raw traffic data can also be saved for further analysis.