@vcxiaohan - not exactly diamond shaped, but this WebGL guide also has a few nice gifs and explanations on math and handling of diamond-like surfaces (with internal reflections without transparency.)
This topic and answers to it may also be quite helpful.
@drcmda it’s not about secrecy - all the math is already there. The main (and kinda only) challenge lies in transparency right now - since diamonds require 2 overlaying transparent surfaces to simulate total internal reflections (and overlaying transparency is easy neither in WebGLRenderer, nor in postprocessing.)
Writing and open-sourcing a “fake” diamond shader (1, 2, 3) isn’t that hard, but will likely lead to an example like Water / Water2 - where the amount of limitations and “assumptions” makes them not really universal / maintainable. And in case where code isn’t reusable outside one project - we’re happy to give answers and help, but expect the other side to do the keyboard tapping 