A value of 0 for fGammaCorrection in CMP_CFilterParams when used in CMP_GenerateMIPLevelsEx would use a gamma of 0, but the documentation says a value of zero would result in no correction

// Apply Gamma correction to RGB channels, using this value as a power exponent,value of 0 or 1 = no correction

The documentation seems more correct, as usually a "zeroed" out struct should result in a sensible default.