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Developer Diary #7 - The Economic Model


The past week I spent a lot of time reading through papers and literature on urban economics - I want the economy in Citybound to be as closely implemented to actual research as possible.

There are many approaches and methodologies - but one struck me as the most simple and elegant: the tried and true Monocentric city model.

 The Monocentric city model is the cornerstone of urban economics since its formulation in  the decade of 1960 by Alonso, Muth and Mills. Source

I wasn't quite sure if I could trust such comparatively old research, but many modern approaches refer to this model and still praise its accuracy:

 The implications of the monocentric model, especially for the relations between distance to the Central Business District (CBD) and population density, housing prices, land rent and  capital/land ratio are widely known and have been tested many times for a great number of cities and countries. Source

When I started to read about how the model works in detail, and how that could be represented in gameplay in Citybound, I became very excited!

   Consider a city in a featureless plain  The optimal, cost-minimizing shape of a city is a circle  The city has a fixed population level N  All workers must commute to the central business  district (CBD),which is assumed to be a point Source  

Citybound: 2D is enough!

This allowed for some radical simplifications for Citybound:

Here is an early screenshot of my first iteration of Citybound towards this new model:

Even better than 2D: 1D

Soon, I found an even more drastic simplification, as described by Ogawa and Fujita:

 [...] with the assumption of a linear or circular city, the spatial characteristics of each location in the city can be described simply by the distance from the CBD. Source

A whole city - described by just a line! Suddenly my dream of simulating multi-million resident cities fluently, even on old hardware, became graspable!

Porting all of our graphics and game logic to 1D will take some time, but I was able to create an already impressive sneak-preview of the transition progress: a full-scale, 1D, monocentric representation of zoning and traffic in a 3 million resident city, running smoothly in Citybound:

Citybound - pure minimalistic gameplay

The shift to 1D is not everything. In accordance to the model, the number of citizens and jobs is considered constant. Gameplay thus reaches its minimalist peak: you simply set the size of your city, number of residents and number of jobs, and watch the city reach its economic equilibrium. A truly zen-like experience.

What Michael's been up to

As always, Michael quickly adapted to this shift in vision for the game and is already porting his polygon-skeleton algorithm (and the whole geometry library!) to 1D.

This means that we will be able to have fully procedurally generated, complex buildings in Citybound, even in one dimension!

I hope you're all as excited about these changes as I am - you will hear from me soon!

→ Discussion on /r/Citybound