Work with GIS data

To access the tutorial projects in ArcGIS CityEngine, open CityEngine and click Help > Download Tutorials and Examples in the main menu. After choosing a tutorial or example, the project is automatically downloaded and added to your CityEngine workspace.

This tutorial was created in collaboration with Devin Lavigne of Houseal Lavigne Associates.

Working with your own data

Working with GIS data is a critical workflow for urban planning. This tutorial introduces the user to GDB imports and how actual GIS information can be used to procedurally create a 3D city.

When existing GIS information exists, CityEngine can import the data and provide you access to geometry along with all its spatial attributes. For instance, a parcel with setback information can pass this information on to CityEngine to quickly generate zoning envelopes, or existing land use information could be used to generate a prototypical building. You may find this particularly useful if you are working on a redevelopment concept or fitting the concept into an existing development context. In this situation, the existing context can be easily generated from existing GIS information, and redevelopment opportunities can be applied to specific parcels.

This tutorial is built around an actual use case, in which CityEngine was used to assist the City of Detroit in quantifying and visualizing infill development. In May 2021, the U.S. Department of Housing and Urban Development (HUD) selected Detroit as a winner of its highly competitive and coveted Choice Neighborhoods grant program. The $30M HUD grant helps bring 500 affordable housing units to Detroit’s Corktown Neighborhood, a revitalizing neighborhood situated west of downtown Detroit.

Detroit’s plan for this area draws upon the Greater Corktown Framework, which was developed following an 18-month effort by the City Planning and Development Department and the Housing and Revitalization Department. City leaders, residents, community organizations and nonprofits, and the private development community worked together to create Detroit’s bid to revitalize areas of the neighborhood and address challenges. The Greater Corktown Framework calls for:

• Replacing distressed publicly assisted housing.
• Improving outcomes of households regarding education, employment, and health.
• Better integrating affordable and market rate housing to ensure a welcoming and diverse community for all.
• Reinvesting in distressed areas to offer amenities and assets, such as improved safety and early childhood education.

As a follow up implementation action to the Greater Corktown Framework, CityEngine was used to visualize the framework’s recommendations and policies, and its dashboards and reporting were used to help inform the grant application and future decision making. This tutorial uses the city’s GIS information to work through this project in a similar fashion.and covers the common workflows and tasks associated with working with existing GIS information.

Importing your data

In the first step of this tutorial, you will import features or layers from a file geodatabase, along with a georeferenced aerial image into your scene.

Import layers

You can import the data with the menu by going to File > Import. Select File GDB Import located in the CityEngine Layers folder in the dialog box.

This opens the File Geodatabase dialog box and allows you to browse to the Corktown.gdb file geodatabase within the \data\ folder of the project.

Alternatively, you can browse to the \Corktown.gdb\ folder within the CityEngine project and right-click the folder and select Import. While this may seem easier, keep in mind that this tutorial has moved the data into this directory for you. The File > Import method allows you to browse to geodatabases anywhere on your computer or network.

Before you import the layers, you want to make sure you uncheck Create Block/Lot Shapes from Graph checkbox. Since you are using actual parcels, you do not need to have CityEngine create blocks and parcels for you.

Uncheck the \Corktown\Buildings_Detroit dataset and click Finish. Once all the data is imported into your scene, it should look like the image below.

Import aerial image

To import the aerial image, browse to the \maps\CorktownAerial\ folder in Navigator. Drag the Aerial Base.jpg file into the scene, which launches a dialog box to complete the import.

Select Texture Import and click Next. On the next screen, click Finish.

Cleaning up the street network

One of the first steps when working with the streets is to perform some common clean-up that can be expected when working with your own data, and then apply a CGA rule.

You may notice that the graph network of street centerlines extends beyond the study area and have different lengths. You want to shorten them, so that they just slightly extend the crossings. This is a more stylistic change, but it looks cleaner and helps to keep the focus on our study area.

Set layer visibility

Begin by manually turning off the visibility for all of the layers except the StreetCenterlines_Corktown layer. This allows you to focus on this layer without the distraction of the other information.

Shorten street segments

Use the Select tool (Q) to select nodes on one side of the street network and click the Transform Move tool (W) to move the nodes to shorten their length.

You may have noticed that using the red or blue arrow drags the nodes along the scene’s world orientation. You can change this behavior by adjusting the orientation temporarily along the street grid using the Adjust Position and Orientation toggle key in the transform tool options or press (o).

Work your way around the study area until you end up with something like the image below.

Fix conflicting shapes

You may notice that one of the intersections has an error that needs fixing. This is called a conflicting shape and it occurs when there is not enough room for CityEngine to create the geometry associated with the intersections and nodes.

Start by selecting the node that is creating the error. Now, change the Curb Radius in the Node Parameters section in Inspector. Change the value from 3 to 2 and the error should be resolved.

Simplify corner

There is one other issue with the data you imported. Probably, either the data included a z value (height), or CityEngine has arced the street upwards at the corner below. With a closer examination, you can see that there are three nodes at this corner. As a general tip, the less nodes/vertices in your graph network, the less conflicts you will have and the easier it is to adjust the graph network.

To remove a node, simply select it, and with the Transform Move tool (W) move it on top of an adjacent node. It should automatically snap and once you let go, the two nodes will merge together. You will have to do this twice at this location.

Adjust corner curve

Once you have one node left, the final cleanup step is to fix the curve and location of this street. Select the last remaining node and then activate the Edit Streets/Curves tool (C). The tool allows you to move the selected node and use the handles to edit the length and arc of the corner/curve. Turn on the Parcels Corktown layer for a guide and use the Edit Streets/Curves tool to adjust the road to fit in between the parcels.

Working with ESRI.lib rules

A CGA rule turns the shapes into 3D models. The rule file you will apply to the streets has already been created and is provided as one of the rules in the ESRI.lib. ESRI.lib is a CityEngine project that contains a library full of useful resources, such as CGA rules and assets. They help you get started with your projects. ESRI.lib is automatically installed in your CityEngine workspace.

Select the street shapes

Select all the shapes associated with the centerlines. There are a few different ways to select objects: manually with the Select tool (Q) , with the Select menu, or right-clicking the StreetCenterlines_Corktown layer in Scene Editor and click Select Objects.

Assign the rule

With all the shapes selected, you can now apply a rule by clicking Assign in the Rules section of the Inspector window. This opens a dialog box in which you can navigate to the ESRI.lib\rules\Streets\Street_Modern_Standard.cga rule. Once you have selected the rule, click Open to assign it to the shapes.

Alternatively, you can directly drag and drop the rule onto the selected shapes from the ESRI.lib project folder.

The street models generate in your scene:

Working with the existing buildings

One of the layers imported into your scene was the Buildings_Corktown layer which contains the existing buildings in the neighborhood. You can use existing information to transform them, with the help of CGA, into 3D models.

Before continuing, make the Buildings_Corktown layer visible and hide all other layers in the Scene Editor.

Object attributes

One of the key benefits and reasons for working with your own GIS information, are the attributes that get mapped to the shapes in CityEngine. The data for the footprints in the project includes five attributes that you can use to drive the generation of your models – STORIES (for height), and DESCRIPTION (for roof forms), and RED,GREEN, BLUE (for the building’s color).

Apply Detroit buildings rule

Use the DetroitBuildings.cga rule located in the \rule\ folder to apply to the existing buildings. This process is the same as to how you applied rules to the streets earlier in the tutorial. Right-click the Buildings_Corktown layer and click Select Objects. Now, you can assign the rule in Inspector, as you did with the streets, or drag the DetroitBuildings.cga rule from Navigator onto the selected building shapes.

The only difference when assigning the rule through the Inspector window is that the shapes won't generate automatically. Click the Generate Models tool (Ctrl+G) to generate the models.

Automatic field mapping

The 3D models generate automatically because of the way the data was prepared and how the CGA rule was written. Since the CGA rule contained attributes with the same names as the fields from the GIS data, the field mapping occurs automatically. So as soon as you apply the rule, it's extruded to the proper height, colored according to the RGB values in the GIS, and a hip roof is applied if the DESCRIPTION attribute is set to Single-Family Housing.

If you look in the Inspector window, you can see that the (Object) word is in italics next to the attributes. This is informing you that this CGA attribute is provided a value from the attribute of the object or shape. Note, that you can override any of these attributes by changing the values in the Rules or Object Attributes section. You can view all of the values in this section.

Rename the layer

With the buildings extruded and colorized, you can rename the layer to help you organize your scene. Rename the layer to Buildings-Land Use. You can rename layer in the following ways:

• Double-click the layer’s name.
• Right-click the layer and click Rename.
• Select they layer and type a new name in Inspector.

Zoning envelopes

Often community planners need to visualize how the zoning regulations impact what can be built on a parcel of land. With CityEngine, this is an easy process, especially since you have already identified and set the parcels on the streets.

Next, you'll using zoning information from the parcels to create zoning envelopes to help you visualize how required setbacks and building heights limit the placement and construction.

Adjust the Scene Editor, so only the shapes from Parcels_Corktown layer are visible.

Assign street edges

Since you are using your own parcel data and not the shapes that CityEngine creates from the street network, you need to identify the edges of each parcel that are facing the street. This is a manual process of selecting the edge of the parcel that faces the street and selecting Shapes > Set Street Edges in the main menu.

Change your view so you can drag a selection box around multiple street edges at once.

Setup a keyboard shortcut

When you do a process like this, you may find yourself spending a lot of time accessing the tools in the menu. To speed things up, consider setting up a shortcut. To setup a shortcut, click menu Edit > Preferences in the main menu. Search for Keys. This allows you to bind a key stroke, or a combination of keystrokes, for the menu tool. In the example below, the keyboard shortcut for Set Street Edges has been configured to Ctrl+Shift+E. Now when you select an edge or group of edges, that key combination quickly sets the edges to street edges.

Applying a rule to parcels

To select all of the parcels, right-click the Parcels_Corktown layer and click Select Objects.

The ZoningEnvelope.cga rule is located in the \rules\ folder. It is a simple rule that works with the attribute data from the file geodatabase parcels and automatically transforms setback information into a simple zoning envelope.

With the parcels selected, drag the rule from Navigator onto one of the parcels.

Automatic attribute mapping

Similar to the existing buildings, the parcels and the ZoningEnvelope.cga rule were prepared with the same fields or attributes, and as a result, the field mapping occurs automatically.

You may encounter some shapes where the front and back are flipped. This is because the street edge was not set for one reason or another. To resolve this, you can just repeat the process of assigning the street edge for these shapes. In the end, the result should look similar to the image below:

Since the parcel layer is now 3D zoning envelopes, rename the layer to Zoning Envelopes to help organize the scene.

Infill development

As part of the HUD grant, the City of Detroit will bring in more than 500 new units of affordable housing to the rapidly redeveloping Corktown neighborhood. Over the last several decades, the Detroit Land Bank Authority has been acquiring dilapidated and vacant parcels as part of their mission to return the city's blighted and vacant properties to productive use. The next part of the tutorial transforms parcels owned by the Land Bank Authority into 3D development models.

Duplicate the buildings layer

Start by turning off all of the layers, so nothing is visible. Next, click the Buildings–Land Use layer in Scene Editor to select it. Then click Layer > Duplicate in the main menu to make a copy of the layer. Rename this new layer to Buildings–Context.

Prepare the context layer

Right-click the Buildings–Context layer and click Select Objects. With all objects selected, change the Color Mode option to White in the Inspector. This helps make the existing buildings less prominent.

Delete buildings on Land Bank parcels

Turn on the visibility for both the Landbank_Corktown and Buildings–Context layers, and make sure to turn off all the other layers. You will notice there are some buildings situated on parcels owned by the Land Bank. These homes have likely either been demolished already, or are planned to be demolished, to make the parcels available for new construction. Moving through the scene, select any building that is on a Land Bank parcel, and press the Delete key.

Apply redevelopment rule

Select all of the objects in the LandBank Corktown layer, apply the LandbankDevelopment.cga rule to the shapes/objects, and click the Generate Models tool (Ctrl+G) to create 3D models. This rule applies the City’s zoning regulations to the parcels and generates a new home on the parcel.

Assign street edges

Now things may not look like expected, because similar to the parcel layer, CityEngine needs you to identify the edges of the Landbank_Corktown parcels that are facing the street. As before, this is a manual process of simply selecting the edge of the parcel that faces the street and clicking Shapes > Set Street Edges in the main menu. Again, you may find it easier if you change your view so you can drag a selection box around multiple street edges at once and set the street edges to many objects. Move through the scene and make sure all street edges are set.

If CityEngine gets slow because of all the tree models, consider changing their representation in the Inspector from Realistic to Fan.

Editing parcels and attributes

While this rule generates viable redevelopment in most cases, there are some parcels with unique shapes that do not produce realistic buildings. Not to worry, this happens all the time in the real world, and it is one of the primary reasons properties are subdivided and consolidated, and why owners petition for variances or relief from zoning requirements. The next part of the tutorial focuses on edits to the shapes and changes to the attributes to complete the development. Notice that the some of the techniques below are performed on the shapes, and others tweak the attributes of the 3D models in Inspector. The F12 key is a useful shortcut to hide and show the models, allowing you to toggle between the most useful view state to perform your edits. You can also manually toggle these on and off by clicking Models in Visibility settings .

Split large parcels

There are a couple of larger lots that can be split to accommodate two homes. Select the shape by clicking it. Press the I key to isolate the selection – hiding everything except the selected parcel. Next, press the F key to frame the selection – zooming in on the parcel. Click the Polygonal Shape Creation tool (S) or click Shapes > Polygonal Shape Creation in the main menu. Hover over the shape near the midpoint, and CityEngine snaps the drawing tool to the middle of the line. Click to set the line’s starting point. Draw a line where you want to split the parcel, snap at the midpoint of opposite edge, and click to finish the line.

Even though it appears like that the line has divided the parcel in two, the process is not complete yet. To finish the split, separate the faces by clicking Shapes > Separate Faces in the main menu. When you do this, the shapes disappear, since you have technically created two new shapes. Press the I key again to exit the isolation mode, and the new shapes, along with all of your other shapes, return into view. Repeat this process throughout the scene, splitting larger parcels into two or more smaller parcels to maximize the infill redevelopment.

Merge small parcels

Another common editing technique is merging two or more shapes into one. There are parcels within your scene that are smaller or irregularly shaped and should be merged into a more suitable parcel. To do this, simply select the first parcel you want to merge, and while pressing the Shift key, select the second parcel. Now, merge the shapes together by clicking Shapes > Union Shapes in the menu. Repeat this process throughout the scene, wherever you think there are two or more parcels that should be combined to produce a more viable building.

Adjust setbacks in Inspector

Once you are satisfied with the size of your shapes, there may still be some houses or 3D models that are not resulting in the development you would expect. Moving around the scene, find any occurrence in which you are not happy with the outcome. Select the shape or model and change the setback attributes – essentially creating an exception or what a planner would call, a variance. This is an iterative process that may also require you to change the location of the front yard by setting Street Edges.

To help you organize your scene, rename this layer to Infil Redevelopment. And while not necessary, you may find it helpful to reorganize the layers, by click and dragging layers up or down in Scene Editor.

Ensure the models are all generated and visible and your scene should look like the image below:

Add context

Before you export, add one final layer to the scene – a layer of buildings surrounding the site to provide additional context for your model. The Corktown neighborhood is just west of downtown Detroit, and the additional buildings will help your scene.

Import existing building data

You can import the footprints for the contextual buildings in the same way as you did at the start of the tutorial. Click File > Import in the main menu. Next, click CityEngine Layers > GDB Import. Click Next. Browse to the \data\ folder for the project and select Corktown.gdb. Finally, select only the Buildings_Detroit layer and click Finish.

Rename the Buildings_Detroit layer to Buildings–Detroit.

Apply the CGA Rule

Select all of the new building footprints by right-clicking your new layer and select Select Objects. With all of the new building footprints selected, drag the DetroitContextBuildings.cga rule onto the footprints. This assigns the rule to all the selected shapes and generates the models:

Exporting

CityEngine provides several ways to share or export your 3D models or imagery. This part of the tutorial walks you through a couple of use cases – exporting imagery and exporting a 360 VR Experience.

Set bookmarks

Setting bookmarks allows you to store the camera’s view and be able to return to that position at any time. Setting the bookmarks also provide additional functionality for some of types of export formats, including the 360 VR Experience.

To set a bookmark, click the Bookmarks menu and select New Bookmark.

Export snapshots

One of the most common and easiest way to convey your work in CityEngine, is through imagery that you can use in reports, documents, or in ArcGIS StoryMaps. To export a snapshot of your current view, click the Bookmarks menu and select Save Snapshot. This exports the current view and opens a dialog box that allows you to change the size of your export image and location. The default settings are set to your Viewport size and saved to the \images\ folder. Snapshots are exported in the .png file format.

Export 360 VR Experience

To export a 360 VR Experience of your current scene, click File > Export. This opens an Export dialog box that allows you to export your scene in a variety of formats. Click Export 360 VR Experience and select Next.

Configure 360 VR Experience

The Export 360 VR Experience window appears, allowing you to customize the 360 VR Experience. You can configure multiple scenarios using the Layer Composition option. For each composition, you can configure which layers should be visible. By default only a single layer composition is added. Additional layer compositions can be added using Layer Composition Operations. Ensure that you check multiple Bookmarked Views checkboxes.

Using the layers you created in this tutorial, prepare three different layer compositions:

1. An Infill Development composition, with the layers Streets, Buildings – Context, Buildings – Detroit, Infill Redevelopment, and Aerial Image checked
2. A Zoning Envelopes composition, with the layers Streets, Zoning Envelopes, Buildings - Detroit and Aerial Image checked.
3. An Existing Land Use composition, with Streets, Buildings – Land Use, Buildings – Detroit and Aerial Image checked.

Click Finish to create the file.

View the 360 VR Experience

If you accepted the default location, the 360 VR Experience is exported to the \models\ folder. Right-click the file in Navigator and click Open With > 3VR Web Viewer.

Within CityEngine, this launches a browser window in which you can view the VR. However, the real impact of this export format is noticed when you view it with a VR device, such as Oculus Quest, with its VR browser.

Be sure to check out the other Essentials tutorials: CityEngine tour and Rule-based modeling.

To continue your learning with CityEngine, see the complete CityEngine tutorial catalog.