I faced a problem in houdini engine for unity:It's seems like the Principled shader in Houdini18 can't convert the HoudiniSpecularVertexColor in Unity rightly.There's no Metallic channel(and other channel) in Default HoudiniSpecularVertexColor shader in Unity.

The unity defalut shader has color,shiness(roughness),nomal channel.I don't know where's the other channel?
I try to do a lot ande failed:
I try to write a new shader to displace the defalut shader and use it as default shader vis modify the setting panel,it go wrong.

I want convert all channels in houdini HDA to unity's shader.How to do that?