Horizontal illuminance error

Hi everyone,

I am working on a lighting simulation where I need to maintain a fixed average horizontal illuminance of 500 lux at a height of 85 cm. At the same time, I am calculating vertical illuminance levels at 120 cm using various calculation angles.

The Issue: Whenever I change the calculation angle for the vertical illuminance (the vector input), my horizontal illuminance results at 85 cm also change. Theoretically, as long as the light fixtures, geometry, and surface reflectances remain constant, the horizontal illuminance should stay the same regardless of the vertical calculation angle.

I suspect there might be a data management or sensor grid grouping issue in my script, but I haven’t been able to isolate it.

I am attaching my Grasshopper file via the Drive link below for reference. Any insights or suggestions on why these two independent metrics are affecting each other would be greatly appreciated!

Drive Link: Ladybug-Honeybee-Electric Lighting - Google Drive