Ugh! Those sites will do absolutely nothing to teach you how to make something like this. Thebookofshaders and shadertoy are about solving a puzzle "given only

Ugh! Those sites will do absolutely nothing to teach you how to make something like this. Thebookofshaders and shadertoy are about solving a puzzle "given only a single function who's input is the position of the pixel being draw, draw a pretty picture with math". That is not remotely related to the techniques used to make something like this paint program. I don't have a suggestion for the paint program in particular. There are a few S.O. answers that cover painting linked here https://webglfundamentals.org/webgl/lessons/webgl-qna.html https://webglfundamentals.org/webgl/lessons/webgl-qna.html