irradiance VEX function
Computes irradiance (global illumination) at the point P with the normal N.
See also: occlusion, pathtrace

vector irradiance(vector P, vector N)
Computes irradiance (global illumination) at the point P with the normal N.
Keyword arguments
See optional parameters.
adaptive  1 or 0 
Turns on an automatic optimization that will reduce the number of samples when there is little variation in occlusion above the sample point. This can improve performance at the expense of some possible flickering or additional noise. 