Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Blur Offset
SHADER_MIPOFFSET
Parameter: Blur Scale
SHADER_MIPSCALE
Parameter: Override Defaults
SHADER_GPUTEXENABLED
Parameter: Texture Size X
SHADER_GPUTEXSIZEX
Parameter: Texture Size Y
SHADER_GPUTEXSIZEY
Parameter: Texture Bit Depth
SHADER_GPUTEXBITDEPTH