TressFX 4.0 hair rendering

“SamplerMask”
RHISetBlendState(FBlendStateRHIParamRef NewState, const FLinearColor& BlendFactor, uint32 SamplerMask)
or
“SampleMask”
RHISetBlendState(FBlendStateRHIParamRef NewState, const FLinearColor& BlendFactor, uint32 SampleMask)
or
“”
\Engine\Source\Runtime\RHI\Public\RHICommandListCommandExecutes.inl
INTERNAL_DECORATOR(RHISetBlendState)(State, BlendFactor);
?