I've learned how to write basic JSON files that work with vanilla shader templates (like the spider eye or blur effects). However, I don't understand how to access uniform variables. For example, I want to create a blur that fades in smoothly over time. I'm also interested in how to stack or overlay shaders on top of each other — the way mods like Blur and Enchanted Visuals do it. Could anyone explain the general approach or point me to relevant resources for Forge 1.20.1?