Point-in-time Illuminance

This page describes the simulation settings and result outputs specific to the Point-in-time Illuminance calculation. For general information about the Daylight tab, including how to define and edit Optical Properties and Measuring Planes, please refer to the generic Daylight tab documentation.

Point-in-Time Illuminance refers to the amount of light (measured in lux) falling on a surface at a specific moment in time, based on the actual position of the sun and the sky conditions for that date, time, and location. Unlike the Daylight Factor, which uses a fixed overcast sky, Point-in-Time calculations use sun and sky models that vary with time, allowing users to analyze how daylight performs in real conditions—whether for a typical day, a critical hour, or during specific seasonal scenarios.

Calculation settings

The following settings control how illuminance is calculated at specific moments in time:

Calculated Time Points
Define the moments in time for which illuminance will be simulated. Use the "+" button to add new time points. To remove a time point, right-click it and select Delete.

Type of sky
Choose from four predefined sky models or a climate-based sky. When a climate-based sky is selected, sky conditions (including irradiance) are drawn from the climate file at the selected time point.

Precision
Set the detail level of the Radiance calculation. Click the Precision link to view or edit specific Radiance parameters or to create custom precision settings. For more details see the page Radiance workflow and parameters.

Controllable shading
Define how internal shading devices (e.g., blinds) are treated during the simulation:

• None drawn: All controllable shades are fully retracted.
• All drawn: All controllable shades are fully deployed.
• According to control signal: Each shade adopts the state it had at the specified time point in the selected control simulation.

Simulation with control signal
If "According to control signal" is selected, specify the simulation that provides the shading control data. This simulation must include the "Shading control" output as part of its logged results.

Optical properties

See Daylight tab > Optical properties.

Measuring planes

See Daylight tab > Measuring planes.

Illuminance results

After the simulation is complete, Illuminance metrics are displayed in the results table for all selected zones and measuring planes. When Illuminance is selected from the first row of radio buttons, a second row appears allowing you to choose the specific time point for which results are shown.

The following scalar values are calculated by spatially aggregating the illuminance results over each measurement grid:

• Median Illuminance: Median illuminance value on the measuring plane (lux)
• Avg Illuminance: Average illuminance value on the measuring plane (lux)
• Min Illuminance: Minimum illuminance value on the measuring plane (lux)
• Max Illuminance: Maximum illuminance value on the measuring plane (lux)
• UR (Illuminance): Uniformity ratio, calculated as the minimum divided by the average illuminance

Within the table, you can:

• Select and copy individual cells to paste into other applications,
• Sort the data by clicking on a column header,
• Export the entire table to Excel, and
• Visualize a metric directly on the 3D model by clicking the box icon  in the corresponding column header:

In addition, you can visualize a heatmap of illuminance values on each measuring plane directly in the 3D view. To do this, select Illuminance from the variable list in the 3D visualization interface. Use the Visualization slider  to browse results across multiple time points.