This is an implementation of sumi-e (Chinese/East Asian painting) shader on Godot. To access the demo, open src/Sumie.tscn. The shader files are located in the assets folder. Basically, there are 2 shaders, a spatial shader to be applied to the meshes (SumiE2.tres), and a post-processing shader (Sumie_postprocessing.tres) to be applied to the final TextureRect node (named 'View' in the demo). You can access and modify the shader through Godot editor.
[1] Park JH., Kim SJ., Song CG., Kang SJ. (2009) Hardware-Accelerated Sumi-e Painting for 3D Objects. In: Allen G., Nabrzyski J., Seidel E., van Albada G.D., Dongarra J., Sloot P.M.A. (eds) Computational Science – ICCS 2009. ICCS 2009. Lecture Notes in Computer Science, vol 5545. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-01973-9_87