Posted by gouessej on Jun 29, 2023; 8:03am
URL: https://forum.jogamp.org/How-do-I-use-stencil-textures-for-outlining-shapes-tp4042652p4042719.html

Relying on glLineWidth() isn't future proof but I have no alternative to suggest yet.

Would it help?
https://github.com/connor-penrod/cel_shading_opengl