path-waves script to make spikes on circle help.

[rich2005]

You should not be using that video, it is old (2012) , out-of-date, there are better ways using scripts and plugins. I must get round to deleting those old Gimp 2.8 videos.

You found the triangle option in Ofnuts plugin 

Looks like this, then path to selection and a fill. This using a gradient.