Drape with radius possible in sketchup?


A bit of background: I’m a lightning protection designer and when working on projects we have to determine areas on the exterior of a building that fall under a zone of protection using NFPA-780, areas that don’t fall under a zone of protection will then require a lightning protection system installed on that area. To do this you have to imagine a 3d sphere with either a radius of 150’ (most common) or 100’ and roll it all over the building (also tangent to the ground) and, everywhere the sphere touches the building will then require lightning protection.
Would it be possible for someone to write an extension to do this in sketchup and have the areas where the sphere touches be a different color possibly using a sort of drape tool feature to do a quick analysis on a building?

My apologies if I have posted this in the wrong area.


Hi Matt,
To help you, we need to understand exactly what your goal is.
Being unfamiliar with NFPA-780, I couldn’t quite picture your description of the rolling ball method.

Does this Lightning Protection Guide by Underwriters Labs correctly describe what you’re after?
Here’s the link…


Thanks Geo

Yes, here are some youtube videos that may help explain it better as well.


One thing here is for certain; I am not an extension developer.

Nonetheless, based upon what we’ve seen accomplished via extensions over the past few years, I would guess a talented developer may well be able build an extension to suit your needs; especially when they have in hand the parameters/formulas presented in the 2nd video.

The ‘blue tent’ depicted in the 1st video is the modified product of a Follow Me extrusion.
Your title is a bit off target as modeling the’ tent’ wouldn’t necessarily involve SketchUp’s Drape tool.


Hi mmalensek,

I just saw your message about that ‘drape’ as you call it.
I am also a lightning protection engineer, and as SketchUp is so easy to handle, I would love ot have such extensions to assess protected and unprotected zones.
As I live in Europe, I do not apply NFPA 780 but IEC 62305. Nevertheless, our goal is the same.
I have some good skills in computer science and developping and I would love to make a try, writing codes for that extension.
But, I have no idea what code is used and I have no idea where to start?
Is there any list of existing functions that I could reuse? do I need a specific software to write the code?
If Geo or someone else could help me out with this, I would really appreciate it a lot.
The code should not be too difficult to write I think.
Thanks to those who will reply to my message.
Kind regards,

Clément B.


the API for SU is found >> here <<

@jimhami42 or @TIG may be able to offer advice on getting the formulas into ruby…



Thank you John,
I took a look to the class Index and it will be useful for me :smile:
I will contact jimhami42 and TIG to have some tips.



As @Geo pointed out, the video showing the SketchUp animation is created by using the follow-me tool. I’ve created a simple model to demonstrate how you would do this to illustrate the protection zone:

rolling_sphere.skp (1.5 MB)