Gives access to input variables (built-ins) available for the shader. See the shading reference for the list of available built-ins for each shader type (check [code]Tutorials[/code] section for link). https://docs.godotengine.org/en/stable/tutorials/shading/shading_reference/index.html One of the several input constants in lower-case style like: "vertex"([code]VERTEX[/code]) or "point_size"([code]POINT_SIZE[/code]).