Some Issues with LB SunlightHoursAnalysis

Hello dear Ladybug community,

I had some issues with significantly different results when I was re-running and update a old file.
I was trying to customize according to my needs, the “Find when sun is visible to a point” script,
but I noticed strong inconsistencies compared to the months before, where I did not find any problems.

mostly I have 2 problems…

…the first problem is that several sun rays are not blocked from the context.
(see the image). I checked the direction of the surfaces in Rhino and are all in the right direction.

…the second problem I noticed is that there are strong inconsistencies, changing the time step from “every hour” to “every minute”

I found the problems by testing the script on different models,
The test model and GH script are attached here.
Simple-Modell.3dm (440.5 KB) (508.2 KB)

I hope that some of the experts and/or administrators will be able to spend some of their precious time, checking and removing the doubt that I am wrong.


1 Like

… I solved the second problem, I had forgotten to Graft the component that generate the all visible sun vector to my input points.

Unfortunately I can’t solve why all the solar rays are not blocked by my context.
The first image is how it comes out SunlightHoursAnalysis, in the 2nd image they are the only sun rays that should be displayed.

I am attaching the updated file. (586.9 KB)


Is it possible that you’re mapping there data incorrectly? What happens if you run it only for the center of the face? Does the result for a single point looks right?

Dear mostapha,

The result for a single point is better but the unblocked rays remains in some areas (see the Image).
The problem is that many times, require me to analyze surfaces (fasade) and not single points (windows), so the problem and the doubt would remain.

I don’t think I’m wrong with the mapping, because the rays come out of the output: SunIsVisible (see the image)

thanks for answering me.


Dear @mostapha, I got your script " Find when sun is visible to a point" and added an obstacle.
Here too, I have the same problem. As you can see in the image, some rays that should be blocked, pass through the surfaces (orange circle)

Unfortunately I have to prove to my superior the exact time span of direct solar radiation, and if he sees that some of them pass through our context, he questions the functionality of this analysis.!

I really hope, you have the time to check this problem.

With best regards
Liam R.

Hi @LiamRuvio,

There were two issues:

  1. You forgot to connect the blocking geometry to context.

  2. You should use sun vectors to re-draw the lines and not the sun positions. Sun positions are calculated in relation to the center of the sunpath. You have to calculate the sun position for each test point based on the sun vector.

Here is the results for timestep 4.

Here is the updated file: (591.6 KB)

The second issue was the main point.

Thank you for solving my problem, for your time and for what you do!!!


Hello, I came across the same problem with rays that appear to pass through surfaces. Unfortunately, I am using LBT 1.4, so some of the parameters are named different or in a different position.

The second problem I am facing is, the generating of the graph, showing the hours when the sun is visible. It also seems that I do not understand exactly how LB Construct Data/Headers work.

I am not so sure which output is needed, and where to get, so that I can get the data I want.

PS I love seeing what you guys have done with LB over the years. Thank you all for the support as well!

Hristo (53.6 KB)