PI is not defined in shaders

[isaacremnant]

Godot version: 3.1

PI is defined in GDscript but not in the shading language. Setting a uniform leads to an extra variable that could be modified through the inspector. Also, even if constants were available (#10577), some basic constants defined directly in the language would be useful. I'm new to shaders, so apologies if this is not desirable.

[CptPotato]

Pi is often used in shaders so I think this is a good idea.

[creikey]

Along with TAU

[udit]

Can this be added to 3.3?

EDIT: nvm, I just saw it was added to 3.4 milestone

[clayjohn]

@udit No, 3.3 is receiving bug fixes only. There is a PR open to add PI, TAU, and E to 3.4, but there is still ongoing discussion about whether breaking compatibility is worthwhile #52315