Hey @saitot ,
Good question.
RGB has 3 values RED, GREEN and BLUE, hence float3.
Luminance only has 1 value, hence float.
Luminance is the intensity of light emitted from a surface per unit area in a given direction.
Its similar to brightness, where luminance is measured (cd/m^2) giving a single value, brightness is perceived and cannot be measured objectively, but scaled as a percentage.
For the night vision shader, every object is seen in the same shade of green, only with different luminance values (brightness)
I hope this makes sense.
