Hi, no time now to clean up the code, make it easier to use or write about it, but here is an early version of the blur: https://github.com/hamoid/Fun-Programming/tree/master/processing/ideas/2018/11/pingPongShader
Also more details about the project: Album cover for Floating Spectrum
Cheers!
ps. And the way to give a line thickness: https://github.com/hamoid/Fun-Programming/tree/master/processing/ideas/2018/11/lineNormals (then each vertex should have a texture coordinate and call texture() to go in the direction of the images above)