Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Illumination
MATERIAL_PAGE_ILLUMINATIONParameter: Polygon Light
MATERIAL_GLOBALILLUM_AREAParameter: Portal
MATERIAL_GLOBALILLUM_PORTALParameter: GI Generate
MATERIAL_GLOBALILLUM_GENERATEParameter: GI Generate Strength
MATERIAL_GLOBALILLUM_GENERATE_STRENGTHParameter: GI Generate Saturation
MATERIAL_GLOBALILLUM_GENERATE_SATURATIONParameter: GI Receive
MATERIAL_GLOBALILLUM_RECEIVEParameter: GI Receive Strength
MATERIAL_GLOBALILLUM_RECEIVE_STRENGTHParameter: GI Receive Saturation
MATERIAL_GLOBALILLUM_SATURATIONParameter: Caustics Generate
MATERIAL_CAUSTICS_GENERATEParameter: Caustics Generate Strength
MATERIAL_CAUSTICS_GENERATE_STRENGTHParameter: Caustics Receive
MATERIAL_CAUSTICS_RECEIVEParameter: Caustics Receive Strength
MATERIAL_CAUSTICS_RECEIVE_STRENGTHParameter: Caustics Sample Radius
MATERIAL_CAUSTICS_SAMPLERADIUSParameter: Caustics Samples
MATERIAL_CAUSTICS_SAMPLES