LDLib is a libarary mod for custom rendering, modular gui.
LDLib provides a number of renderers, as well as a modular GUI frameworks, including emissive texture supports, custom shaders, and particle systems.
Multiblocked 1.16+ currently uses this mod as a dependency.
Screenshots from multiblocked:
atesla laser
artificial minisun
botania + thaumcraft
renderers
visual editor
auto build