Hello, please post questions on Cinema 4D plugin development in the "Cinema 4D Development" forum. When doing so, please also use the appropriate tags. MATERIAL_GLOBALILLUM_GENERATE is the correct ID of that parameter. You just have to set the parameter value of the material you want to edit: material->SetParameter(MATERIAL_GLOBALILLUM_GENERATE, false, DESCFLAGS_SET::NONE); please notice that the ID is defined in the millum.h header file. If you have general questions on how to handle materials with the C++ API you will find information in the documentation: Materials and Shaders Overview BaseMaterial Manual Material Manual best wishes, Sebastian