Activities and Influences

One of Ürban PAD’s most innovative features is its capacity to algorithmically place parcel templates according to rules that you define in the specification interface. The program places each activity in the space available, taking into consideration the placement of other activities.

You will find the Activities parameter on the City Designer specification screen. You can use the Activities parameter to set up attractive or repulsive relations between different activities.

Activities are the different types of functional entities you find in a city. These can be business buildings, different types of housing for varying income levels, factories, cathedrals, gardens, parking lots, and parks, among others.

The Activities parameter allows you to define which activities will be present in your city.

In City Designer, an Activity consists of one or more parcel templates created with Parcel Editor. This content corresponds to a .gcf file which can be found in the Parcels directory of the City Project Settings.

Composability and Activities

All Activities must correspond to a parcel or parcels created in Parcel Editor. A parcel has a fixed size and shape from which it will not deviate (unless its Masking Policies allows it to be cut during placement during city generation). All versions of Ürban PAD beginning with Ürban PAD 2.5 allow the creation of procedural volumes with Sector Editor.

Unlike a parcel, a sector has no fixed size or shape. Procedural volumes are therefore adaptable to different size and shape constraints. However, these sectors cannot be used directly as Activities in City Designer.

To use sectors (such as procedural buildings) as the basis for an Activity, you can compose templates using a Sector Link. Using a Sector Link will allow you to import sector content to Parcel Editor. Importing sector content to a parcel created with Parcel Editor will allow you to use sector templates in Activities:

• Create the procedural building or element with Sector Editor.
• Save the procedural buildings/elements as sectors. If you wish to put multiple procedural elements in a single sector, you may use a Sector Link rule to compose sectors (see Philosophy for an explanation of Ürban PAD and composability).
• Save the sector.
• In Parcel Editor, use a Sector Link to import the sector or sectors into a parcel template.
• Add a Geometry Scale Positioning Policy to each Sector Link created in Parcel Editor. This operation allows Sector Links to adapt to the available parcel space.
• Save the parcel template created with the Sector Links as a .gcf file.
• When placing Activities in your city specification, use the resulting parcel templates as usual.

Activities Parameters

This section also exists as the :ref:`step3` tutorial on the :ref:`specification` page.

Left-clicking on the Activities sub-menu in the City Designer specification screen reveals activity.

Right-clicking on activity brings up a sub-menu of options:

• Delete
• Rename
• Add Parcel Template

You will need to click Add Parcel Template to add the parcel template(s) that constitute the activity from the file explorer that opens on the right side of the screen.

Each parcel template corresponds to a template that has been created in Parcel Editor.

Nb Parcels Max

Nb_parcel_max is the maximum number of instances of an activity that can be present in the city. (For instance, you want only two nightclubs.)

The default value is 0, which means that there is no limitation on the number of instances of the activity.

Importance

The value of this variable defines the relative power of the activity parcel when it is in competition with roads or other activity parcels for a specific space.

Importance does not have a specific unit of measure. It is represented on a scale from 0 to 1000, with 0 being least important and 1000 being most important.

You always have the possibility to avoid removals by using the Lock function to lock parcels or roads whose position you do not want to change during city generation.

Adding an Activity

To add an activity to a city specification:

• Right click on the Activity parameter
• Left click on Add Activity. This will add a line with the title activity_XY, where XY is a number, to the specification. A sub-line will be titled, area_template_XY, where XY is a number.
• Click on the area_template_XY line to open the file explorer on the right.
• Select a parcel template from the file explorer to add it as an activity.
• Repeat the operation for the number of activities desired.

Distribution

The distribution parameter is an optional parameter that allows you to define the number of each activity you want in your city simulation. In the picture below, you see that there are 5 shopping centers, 5 beaches, and 1 nightclub, for example:

When you enter the desired number for an activity, it is converted into a percentage of the total activities in the city simulation. The percentage corresponds to the proportion of that activity in the simulation. The total percentage is listed at the top of the distribution interface, although you cannot see the percentage for an individual activity.

When you launch the simulation, the city generator will place activities in these proportions. If the total percentage adds up to less than 100, the city generator will augment the proportion of each activity to preserve the ratio between the activities.

Note that you are not required to specify a number for any of the activities. If no numbers are specified, the city generator will produce from your specification a simulation with random and variable proportions.

Influences

The Influences parameter is one of Ürban PAD’s most useful features. You can use Influences to create positive and negative attractions between activities.

This functionality is especially useful for automatically creating areas of urban density. Creating a positive attraction between two activities brings them closer together with a specified intensity and over a specified Range. Creating a negative attraction (or repulsion) between two activities pushes them apart.

The following section contains a brief explanation of intensity and range, as well as how to create an influence.

For a more comprehensive explanation of Influences and a tutorial on using this parameter, please refer to Using Activities and Influences to Group Buildings Together. This tutorial is part of the City Project Tutorial: Ocean Isle.

Intensity

Intensity refers to the strength of the influence. It is contained in the range [-99,100]. The closer the number is to either end of the scale (-99 or 100), the stronger the force will attract (100) or repel (-99) other activities.

A negative value signifies a negative attraction, while a positive value signifies a positive attraction. It might be helpful to think of these forces in terms of push/pull (negative/positive).

Range

Range is the distance, in grid squares, over which the influence force is applied.

The range value represents the percentage of decrease of the intensity applied to grid squares at a specified range. This is represented by the decrease percentage parameter.

In the example below, an influence rule defined as Building/building with an intensity of 80, range of 3, decrease percentage of 70 means a building will attract around itself other buildings with an intensity of 80 in its square.

This influence will decrease over the range of 1 to 3 squares by 30%. Here, 70 as a decrease percentage value means that the influence will be applied at 70% strength over the specified range. The actual “decrease” in the decrease percentage value will be 30%. At a distance of 4 squares, the influence propagation ceases.

Creating an Influence

Complete the following steps to create an influence:

• Click on the Influences parameter to access the menu at the right of the screen (accessible by clicking on advanced).
• The activities will appear in two identical columns.
• Select an activity in the left-hand column, then an activity with which you want to create an influence force in the right-hand column. (The photo above shows a relationship between office_building and office_building.)
• After you have selected the two activities, the Intensity and Range fields will appear.
• Enter the Intensity and Range values.

You have now successfully created an influence.

Variance

This variable, which is expressed as a percentage, modifies the importance of the activity. If the importance is 500 and the variance is 10, all the parcels built on the map will have an importance ranging from 450 to 550.

Can Be On City Border

This option allows an activity parcel to be built on the external border, or world sector, of the city. It also allows you to decide not to build activities here.

Is Coeff Absolute

This is an advanced parameter. If you specify in the Distribution value that a specific parcel - Houses, for example - make up 50% of the total parcels, is_coeff_absolute will constrain the activity choice at each instance of parcel placement.

Example: A house, a shopping center, and a restaurant are the three parcels making up your Activities.

If you specify that 50% are houses, then the city generator will have the following probability of selecting any one parcel at each instance of parcel placement: House 50%, Shopping Center 25%, Restaurant 25%.

This behavior contrasts with what happens when is_coeff_absolute is not selected: the simulator will aim for a general goal of 50% Houses, without imposing the restriction on individual instances of parcel placement.