Urban surface materials constitute the primary interface between the built environment and atmospheric boundary layer processes. Materials such as asphalt, concrete, gravel, or vegetated surfaces directly influence radiative exchange, heat storage, evapotranspiration, and surface roughness. These properties shape pedestrian-level thermal comfort and determine how heat accumulates or dissipates across public spaces.

While design guidelines often prescribe vegetation coverage targets, the microclimate implications of specific material compositions and spatial distributions remain underexplored in practice.

This workflow demonstrates a systematic parametric investigation using the infrared.city Grasshopper connector to quantify how ground material configurations affect UTCI distributions across an urban plaza. By varying material area percentages through algorithmic control, we establish performance correlations that support evidence-based surface design decisions.

You can download the ready-to-use Grasshopper file filling the form and start exploring alongside the blogpost.

• Starting a project: If you’re unfamiliar with the basics, check out the Running Your First Simulation Guide which walks through the setup and launch of environmental simulations step by step.

• Using the Grasshopper plugin: To get comfortable with the connector workflow, see Getting started with Connectors: infrared.city in Grasshopper where the process of linking simulations directly in Grasshopper is introduced.

The new feature enables designers to:

• Modify existing ground material types
• Adjust spatial distributions
• Run simulations and evaluate thermal comfort impact

This enables a systematic evaluation of diverse open-space design strategies, particularly during early stage conceptual development.

From Web App to Grasshopper: Accessing Project Assets

After creating your project in the infrared.city web application, you can directly continue working in Grasshopper.

Simply:

1. Log in to the plugin
2. Load your project using the Load Project component
3. Connect the Project ID as usual

What’s new in this workflow is the Explode Project component.

The Explode Project component (located under the Account tab) allows you to deconstruct and access all project assets individually.

Once connected to the Project ID, the component outputs:

• Analyses
• Buildings
• Vegetation
• Site
• Boundary
• Ground

This enables a more precise and technically controlled workflow by allowing users to:

• Validate the exact spatial extent of the simulation domain
• Inspect the relationship between the selected site and the broader boundary conditions
• Confirm geometric consistency between design inputs and the computational analysis grid

Users gain structured access to individual project data layers, enabling full transparency and parametric control directly within Grasshopper.

Inspecting Ground Material Definitions

To analyze the ground material configuration of your project, use the Deconstruct Ground Materials component.

By connecting the Ground output of the Explode Project component to its input, the plugin extracts and separates all assigned surface materials into individual outputs, including:

• Asphalt
• Concrete
• Soil
• Vegetation
• Water

Each output returns the corresponding Brep or Mesh geometries assigned to that specific material category.

This allows you to:

• Inspect the spatial distribution of each surface type
• Quantify material-specific areas
• Review how the site is currently classified before modification
• Validate material assignments prior to simulation

Because the geometries are separated by material type, you gain granular control over the project’s surface configuration. These outputs can be directly edited, replaced, or re-routed into a new Construct Ground Material workflow.

This step transforms ground materials from static project attributes into fully editable parametric inputs within Grasshopper.

Visualizing Ground Materials: Mesh or Brep

A new toggle allows users to display ground materials either as:

• Mesh representation
• Brep representation

This provides flexibility depending on whether the focus is performance testing or design refinement.

NOTE: If you plan to work with the ground materials already defined in the web application, no additional construction steps are required in Grasshopper. In this case, you can directly connect the Project ID to the Update Project component, trigger the update, and proceed with running the simulation.

The Project ID already contains the complete project dataset. This includes the assigned ground material definitions, selected analyses, building geometries, vegetation layers, as well as the site and boundary configuration. Because this information is stored and structured within the project instance, the simulation engine operates using the fully synchronized model without requiring further material inputs.

Defining and Feeding New Ground Materials

If you intend to modify the ground material configuration or introduce new surface distributions, the workflow continues with the Construct Ground Materials component located under the Elements tab.

This component allows you to explicitly assign geometries to predefined material categories such as asphalt, concrete, soil, vegetation, and water. The geometries are provided as Breps representing the respective surface areas to be reclassified.

Once defined, the output of the Construct Ground Materials component must be connected to the Ground input of the Update Project component. This connection overrides the existing ground material configuration stored in the Project ID and synchronizes the updated surface classification with the infrared.city web application.

IMPORTANT NOTE: The component is designed to ensure robustness during parametric exploration. Empty material inputs are automatically ignored, preventing unintended errors in the simulation workflow. If no material is assigned to a specific region, the system defaults to asphalt as the base assumption.

Because the component accepts Breps as ground surfaces, designers retain full geometric control over the classification process. Any subdivided plaza geometry, parametrically generated pattern, or manually defined surface can be directly fed into the simulation pipeline.

Merging and Editing Existing Ground Material Geometries

When introducing new ground materials, it is not necessary to rebuild the entire surface classification from scratch. Existing material geometries extracted via the Deconstruct Ground Materials component can be selectively reused, modified, or combined with newly defined Breps.

For instance, existing vegetation or concrete areas can be merged with newly generated surface geometries using the Merge component. This enables incremental modification rather than full replacement, which is particularly useful in retrofit scenarios or phased design studies.

If specific geometries from the existing configuration need to be removed, the Cull Index component can be used to exclude selected Breps from the material list. By defining index values parametrically, unwanted surfaces can be systematically filtered out. The remaining geometries can then be merged with newly assigned Breps and reintroduced into the Construct Ground Materials component.

From a data management perspective, it is important to ensure a consistent data structure before feeding geometries back into the material construction component. Flattening outputs where necessary helps prevent nested data trees from causing simulation inconsistencies. Maintaining a clean, flattened structure ensures that geometries are interpreted correctly and mapped to the intended material categories.

Explore the Workflow: Example Definition Available

To support hands-on exploration, we are sharing an example Grasshopper folder accompanying this post.

The case study is based on a plaza-scale intervention in Los Angeles, evaluated under peak summer conditions in August between 10:00 and 14:00, a time window where solar exposure and surface heat accumulation significantly influence pedestrian-level thermal comfort.

Within the example file, you can:

• Introduce a new open space or plaza surface
• Assign it to different ground material categories
• Adjust parametric sliders to redistribute surface areas
• Observe resulting changes in UTCI

The workflow demonstrates how existing materials can be reused and strategically combined with newly introduced geometries. In the provided case, all existing vegetation areas were preserved and merged with additional vegetated surfaces to enhance cooling performance. At the same time, concrete surfaces overlapping with the redesigned plaza zone were selectively filtered out using index-based culling before being reclassified.

This structured approach illustrates how ground material composition can be iteratively refined — not only by adding new surfaces, but also by subtracting or reallocating existing ones.

By downloading the example definition, users can explore:

• Incremental material replacement strategies
• Vegetation–hardscape balance testing
• Surface redistribution scenarios
• Performance-driven plaza optimization

Download the example file and start redefining your ground surfaces as measurable climate parameters, where every material choice becomes a performance decision.