Citybound

Citybound
Promotional cover photo
Developer(s)	Anselm Eickhoff
Publisher(s)	AE Play
Platform(s)	Microsoft Windows, Linux, Mac OS
Genre(s)	Construction and management simulation, city-building

Citybound is a free and open source city-building game currently under development by Anselm Eickhoff.^[1] The code is distributed under the terms of the AGPLv3. The game is currently in the pre-alpha stage of development and started development in March 2014.^[1] The game is intended to have a minimalistic art style with the prime focus on being realistic and accurate city simulation. Citybound is intended to build on games such as SimCity, with plans to incorporate features such as procedural architecture, lane-based roads and agent-based economic simulation. The game will also support large cities and regions that can be simulated at once and not rely on so-called "tiny city lots or artificial city interaction dynamics." Citybound will also offer procedural buildings and a level of simulation that takes into account individual cars and pedestrians.^[2]

Development

Citybound was announced in March 2014 by the developer Anselm Eickhoff, who had been inspired by other city-builder games such as A-Train and SimCity 2000.^[3] The game's development was recorded on the Games Development Blog, noting progress in areas such as a basic economy, agent simulation and road drawing and zoning. In February 2016, Eickhoff elected to rewrite the game in C++ over concerns about writing the game in languages such as Javascript and WebGL.^[4] In December of the same year, Eickhoff announced that the game would be open-source due to concerns of future piracy among other issues. Eickhoff also intended to, later on, move the game towards an open-source but would eventually be also commercially sold. He also decided to use Rust instead of C++, it is the current language in which the game is programmed.^[5]

Intended Features

Architecture

Citybound's earliest prototypes demonstrated a procedural architectural model for the game's buildings, in contrast to the conventional approach of loading buildings into the game from a library of sprites or models.^[6] This would allow each city to develop a unique character, and avoid problems of multiple identical buildings growing near each other. This process would be controlled within the game via a system of architectural standards, written as guidelines for buildings with limitations and recommendations, which could draw upon a collection of assets (such as windows, door frames, or lights) and textures. Different architectural templates could produce different architectural styles for different zoning areas, or different time periods, from the same collection of assets. Both the architectural template, and the collection of assets, could be easily modified by users^[7].

On top of the visual benefits of having a unique and integrated city, the procedural building generation allows for tighter, more organic and more realistic city growth. Buildings are capable of occupying irregular lot sizes, and can change zoning form and function over time (for example, Urban Renewal). Civic buildings such as police stations or schools can grow over time as their needs expand, and buildings can hold multiple unique zoning forms, such as commercial shop fronts on the ground floor with upstairs apartments. A further application of this separation from single-lot construction would be that a property's front lawn could be purchased for a road expansion without destroying the property, for example. A closely built landscape would also allow Citybound to have urban buildings fill their entire lots, in a style previous city simulation games have named "Wall to Wall".

By extension, the design of car parks can be seen as another architectural style with guidelines and limitations, which would allow dynamic and simulated parking on the cites of buildings - a feature which previous games have failed to implement. Parking lots could occupy a more organic space around a building, grow and change over time, and come in multiple different forms and sizes depending on the building. Cars would also be able to navigate such car parks, bringing a key element of realism to the game.

In current prototypes, buildings are simply combinations of cubes^[6] or simple gable-roofed structures^[8], to provide a representation of the urban volume of a city. This feature remains a high priority in the development process

Roads

The transport engine of Citybound is its most developed features to date and was released in the Road and Traffic Prototype 1, the game's first public release in early 2017^[9]. In Citybound roads are defined by the sum of their composite lanes such as traffic lanes, median strips, on-street parking, or bus lanes. New lane additions snap onto the edge of an existing road and the whole constructed road can be drawn together.^[10] The distinction of lanes as independent elements drawn together allows them to separate for much more organic and realistic road junctions entailing merging lanes and on-ramps, slip lanes, and turning lanes.

This basic framework will make adapting the system onto heavy or light rail, as well as complex transport assets such as interchanges and airports, a simple process.

The transport path finding engine allows agents to comprehensively navigate a road system, optimizing their route for distance and time based on surrounding traffic conditions.^[11] This means traffic should filter around individual congested lanes and only enter their turn lane when necessary. This change drastically alters how Citybound's roads react to heavy traffic, compared to games such as Cities Skylines or Simcity, where traffic remains in the lane in which they intend to turn at the sacrifice of time. In simulations and tests, the engine can handle tens or hundreds of thousands of agents without throttling or experiencing lag.^[6]

A large component of the transport engine is the concept of a planning mode, which would allow players to experiment with and design complex transport systems without the need to commit to their construction.^[10] This could be done abstracted from the simulation, in a paused realm, and would be free to the player. Whether for financial or planning reasons, the completed intersection plan could be reserved for a future construction time where it can be funded and constructed.

Economy

With the transport engine mostly complete, Eikhoff has started work on the Economy Prototype. His goals are to have an agent (such as a family member or business) react dynamically to their present situation in life, produce personal ambitions, develop lifestyle habits, and plan for their own short, medium and long term future. These features, if applied on a city-wide scale, would allow the entire population to be dynamic and personal with their occupational and purchasing decisions, and sustain a sufficiently realistic economic model of a city's industry that Citybound can be used as a professional urban planning tool.^[12]

In order to preserve processing power, Eikhoff has designed a needs-based system similar to Prison Architect, which calculates the urgency of individual needs (such as food, money or relaxation) and defines activities by how they impact those needs.^[13] In order to simulate a daily schedule, an agent may enter the game with a predefined tasklist or pattern of behaviour. Over time, this schedule is altered based on the agent's experience with their world and what it offers them (such as bad traffic contributing to a longer time to commute, or a new restaurant offering an opportunity to eat out). This system also allows agents to be influenced by impulse such as from advertising, or by one-time events in their life, such as a promotion or holiday event.

The economic model also intends to allow agents to plan for and execute substantial long term investments, such as buying property or expanding a family. Current limitations in the engine surround how agents within a family or workplace might communicate and coordinate an individual performing an activity for the group (such as one member of a household going grocery shopping), and around how to balance and store ambitions and goals in a way faithful to an agent's individual character and lifestyle.^[14]

A substantial limitation to this engine remains its optimisation. The memory and processing requirements of managing multiple dozen aspects of every agent's actions in a city of several ten thousand agents creates a substantial processing demand. This is a contributing factor why other city simulation games have avoided implementing such models, despite both Simcity and Cities Skylines advertising as such upon launch.^[15][16]

Complex supply chains have been envisaged for many industries, that could utilise natural resources and trade to establish industries that supply specific goods or wealth to a city.

User Interface

The user interface remains a lower priority in the game's development, behind the finalisation of the transport and economic models. Due to the game's open source nature, several community members have improved the user interface of the game, adding conventional mouse and keyboard controls for movement and selection.^[9]

As a distinction from other flagship city simulations, Citybound's zoning interface will be as a brush untethered to roads or other infrastructure. Because of the procedural nature of Citybound's architecture, this interface would also be responsible for all service buildings.^[8] Hybrid zones could be constructed by overlaying zone types, to create zones with mixed use buildings. Key bindings would allow the brush to lock to a road, perhaps at a certain distance to draw uniform zones. In a similar way to other office or creative suite products, other keyboard interactions could lock the brush to the x or y planes to create straight lines of zoning through the city, for a park for example. Zoning would offer guidelines to architectural styles to populate the city.

While undecided, an intention for Citybound's time scale is to find a balance between the realism of a day taking 24 in-game hours to complete, and a pace such that game elements can grow and change at an entertaining rate.

Visualisation

Eikhoff's intentions for the game's graphics are for them to appear as photorealistic. His hope is that any player can capture any moment of any part of their city and have it look as if it were real. His artistic inspiration for the game lies in the minimalist architectural styles of the game Mirror's Edge, with clean, geometric but well lit and textured buildings occupying and interacting with the landscape.^[7]

Eikhoff has studied implementations of lighting engines in games while at university, and intends to implement a low level but attractive shading engine.

Broader ambitions of the game also include dynamic terrain that realistically influences the geography of a city, such as the location of water sources and flooding from rainfall through groundwater.^[17] By extension, this version of the game would also feature dynamic weather that could influence agent behaviour, such as worse traffic conditions during wet weather, or more popular beaches during summer.

As part of a fully dynamic and custom city, it would be possible to include smaller details such as buildings or roads actually constructing themselves, and infrastructure deterioration viable through cracks or fading on the road, for example. Therefore, an industry of maintenance within the game could be established, and give every asset of the game a recognisable age and character, contrasting the new with old.

Modding

Eikhoff has made it clear that he desires every aspect of the game to be easily and comprehensively capable of being modified by any member of the gaming community, through simple and approachable tools, even without the need to understand the game's coding language. The life of legacy games Simcity 4 and Cities Skylines have been substantially lengthened through the work of their modding communities on Simtropolis and Steam respectively, providing accessible enhancements to the gaming experience as they have aged.^[18]

The applications of this approachable modding technique can be seen in how every asset of the game is broken into component pieces. Buildings and architectural templates are conditions for using assets, and assets can easily be imported from a 3d modelling software. Road lanes are individual and can be customised. Activities need only define what needs they influence and under what conditions they operate. New businesses and industries can easy refer to existing supply chains within the game. Lighting Look Up Tables and other graphical mods would also be easily interchangeable or replaceable. This allows the game to be endlessly customisable by the player, either for entertaining fun, for realistic simulation, or for aesthetic expression.

Computation

Because of the computational expectations on the game, Eikhoff intends to build the game to only run on the most powerful of computer hardware. Every component of the game engine thus far has been heavily optimised for multi-core processors to share the computational load.^[19] Therefore, Citybound is expected to require a powerful 6 or 8 core processor as a minimum. However, the expected release is far enough in the future that these processors are projected to be more commonplace. He does not want to compromise the potential of the game engine in order to run on less capable machines, as was the design decision behind several gameplay compromises in Simcity.

Eikhoff has considered the possibility of running the whole game in the cloud, and broadcasting the results of the game to players on local terminals.^[7] This would allow for the simulation of entire city maps at once without the need for individual map tiles, and render more complex features such as weather and photorealistic lighting.

Reception

Graham Smith of Rock Paper Shotgun has expressed an interest in following the development cycle of Citybound.^[20] Nathan Grayson from Rock Paper Shotgun expressed concern that the project was overly ambitious and could "fizzle out before it ever really picks up steam"^[21]

See Also

• City-building game
• SimCity
• Mirror's Edge - which the game's architecture is based on.

References

External links

• Official website
• Official devblog
• Citybound Reddit Community
• Citybound patreon