Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Ray Bias
SLA_DIRTY_RAY_BIASParameter: Maximum Distance
SLA_DIRTY_MAX_DISTANCEParameter: Number of Rays
SLA_DIRTY_NUM_RAYSParameter: Spread
SLA_DIRTY_SPREADParameter: Contrast
SLA_DIRTY_CONTRAST