Large differences between radiation analysis in LB 1.3 and LB 0.0.68

[Julioamodia89]

Hi everyone,

I am currently running a simple radiation analysis in one window. I wonder why there is such a big difference between the two of them, they both have the exact same inputs but the results are quite different. Which of them is the right one? Where is my mistake?
Thanks,
Julio

Estudio radiacion.gh (598.8 KB)

[chris]

The LBT one is more accurate and it’s primarily because it includes the contribution of ground-reflected radiation using an emissive “ground hemisphere”. See here for a longer explanation:

Difference Between "LB Incident Radiation" and "Ladybug Solar Radiation" Components

Good question and this is directly linked to what I said here: In LBT, we do the ray tracing for a full sphere around each point so that we can account for the radiation that’s “reflected” off the ground (technically, we’re doing this by assuming an emissive ground hemisphere that has 0.2 the intensity of the sky hemisphere, much in the same way Radiance does). In legacy, we only looked at the radiation coming from the sky dome, which was ok for some purposes but could be 20% less than expect…

[Julioamodia89]

Yes, that was the main difference.
Thank you for the clarification @chris!

[Nate]

Hi, I think the LBT (1.4.0) “LB Incident Radiation” takes into account the bottom face of a brep/mesh, which overestimates the total radiation from my test. The older one “Ladybug Solar Radiation” works fine, which always assigns 0 value to the bottom face. Maybe this is one of the reasons resulting in the huge difference. And I think there is one more issue regarding the “context” in “LB Incident Radiation” but I am not sure. Looks like the simulation result would not change with the “context” when I tried to simulate the radiation on the bottom face.