Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Samples
CHANLUM_SAMPLESParameter: Inital Offset
CHANLUM_OFFSETParameter: Sample Radius
CHANLUM_RADIUSParameter: Sample Type
CHANLUM_TYPEParameter: Stochastic
CHANLUM_STOCASTICParameter: Gaussian
CHANLUM_GAUSSIANParameter: Shadows
CHANLUM_SHADOWSParameter: Seed
CHANLUM_SEEDParameter: Use Lights
CHANLUM_LIGHTS_MODEParameter: Lights
CHANLUM_LIGHTS