numberOfTextures: Number of textures used by the tri-planar projection.
use: Select the type of position and normal you want to use. You can only use __Pref and __WPref if these primitive variables have been attached to your geometry.
pref: Name of geometry Pref (Maya uses __Pref and __WPref). If empty, we will use __Pref or __WPref, depending on the value of 'use'. If all fails, we will use P.
nref: Name of geometry Nref (Maya uses __Nref). If empty, we will use __Nref or __WNref, depending on the value of 'use'. If all fails, we will use Nn.
coordsys: Name of coordinate system transform (e.g. place3dtexture node in Maya). Standard coordinate systems : 'object', 'world', 'screen', 'NDC'. If empty, we assume 'object' space, which is fine for non-deforming geometry.