Stencil bit exposed to user and not reserved by HDRP. Note that it is important that the Write Mask used in conjunction with these bits includes only this bits. For example if you want to tag UserBit0, the shaderlab code for the stencil state setup would look like:
WriteMask 64 // Value of UserBit0 Ref 64 // Value of UserBit0 Comp Always Pass Replace
Or if for example you want to write UserBit0 and zero out the UserBit1, the shaderlab code for the stencil state setup would look like:
WriteMask MyWriteMask // with MyWriteMask define in C# as MyWriteMask = (UserStencilUsage.UserBit0 | UserStencilUsage.UserBit1) Ref MyRef // with MyRef define in C# as MyRef = UserStencilUsage.UserBit0 Comp Always Pass Replace
public enum UserStencilUsage
User stencil bit 0.
User stencil bit 1.