C Interactive Animation of Cities over Time Paul C. DiLorenzo, Victor B. Zordan, Duong Tran Riverside Graphics Lab University of California, Riverside

C Introduction Cities are dynamic embodiments of the needs and wants of the population it holds Difficult problem to try to capture the dynamics of the city and present the information in an easy and intuitive way

C Parts of a City Break down the city into primitive units –Central Business District (CBD) Economic heart of the city Mostly commercial buildings in this area Usually, have the tallest buildings –Zoning Blocks City block, or larger, area Area assigned a zone type based on a city plan –Residential, Commercial, municipal, and so on

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C Parts of a City Break down the city into primitive units –Central Business District (CBD) Economic heart of the city Mostly commercial buildings in this area Usually, have the tallest buildings –Zoning Blocks City block, or larger, area Area assigned a zone type based on a city plan –Residential, Commercial, municipal, and so on

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C Background Computer Graphics Cities –Capture data; Teller et al. –Hand modeled; Hamill and O’Sullivan, 2003 –Procedural; Parish and Müller; 2001 Building architecture –3D models with photographs Jepson et al, 1995; Debevec et al, 1996; Ribarsky et al, 2002 –Instant Architecture – Heuristic rules plus procedural grammar; Wonka et al, 2003 None of these efforts address the evolution of a city!

C Problem Statement Animation –Two point boundary problem that only manipulates the primitive units Solve using Citysack –Similar to the thief’s Knapsack problem

C Goals Recreate the look and feel of a city growing, or decaying, over time Sociologically based Interactive Minimize the amount of inputs for the user

C Applications Urban development and sociology –Play what-ifs –Determine what factors affect the growth and development of their synthesized city Computer games and entertainment –Evolving cities

C Models of Urban Structure Burgess’ concentric zone model –Segregate land into business, manufacturing, and residential usage –Cities grow radially in a series of concentric regions, surrounding a central business district (CBD)

C Models of Urban Structure Hoyt’s sectoral model –Makes allowance for growth along main arterial routes; highways and railways –Cities develop in wedge-like sectors moving radially outward from the CBD

C Models of Urban Structure Harris and Ullman’s multiple-nuclei model –Land usage depends on a number of separate centers of activity for industry, manufacturing, entertainment, etc.

C Solution

C Solution Create a hierarchical model using the primitive units CBD and other centers Zoning Blocks...

C Overview of System Input Animate City Citysack Render Build City Model

C Overview of System Input Animate City Citysack Render Build City Model

C Defining the Model Zoning Unit Zoning Types Zoning usage assigned based on percentages associated with the Burgess’ regions

C Defining the Model Density –Residential; Commercial –A key measure of land usage Maximum density based on fall-off curve

C Building a Simple (static) City Create empty (undeveloped) zones –Until the city’s area A t, is met Develop zones randomly –Distance is weighted exponentially –Assign zoning usage and density –Until the developed area, A d, is met Make small, uniform corrections

C Demo

C Building more complex cities Geographic Limitations –Image Map Defines water No urban areas Elevation –Steepness threshold for developed zones

C Building more complex cities Multiple Centers –Assign maximum densities, relative rates of growth, and unique orientations –Zoning unit’s maximum density is the largest maximum density of all centers

C Demo

C Overview of System InputRender Build City Model Animate City Citysack

C Animate City User inputs –Number of years –Change in population, physical size of the city Two point-boundary problem –Current state and new state Creates a growth schedule for each year Sends yearly changes to Citysack

C Citysack Map Citysack to Knapsack Knapsack Citysack

C Solving Citysack Generate new zones Develop randomly If city can hold new population, halt Else, redevelop –Solve using greedy approach –Solve using conservative approach –Update city based on approach with the lowest cost

C Demo

C Overview of System Input Animate City Citysack Build City Model Render

C Rendering Zones decomposed –density and zone type Height and number of buildings

C Demo

C Rendering Replaced buildings with commercial libraries Use zoning units to describe more about the city –Combine multiple zones Large parks –Break down zones Buildings Houses Trees

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C Conclusion Reduce city to primitive units Build city using these primitive units Simplify animating the city by adjusting the zoning blocks –Solve with a well known algorithm

C Future Work Add roads –Main transportation networks Hoyt’s sectoral model –Inner roads Visual appeal –People, traffic, etc… Added factors –Fire damage, demolition, vandalism

C Thank you!!!

C City InfoCity Center Info Image Map Inputs City History Zoning Info