Is it possible to use say the SOP Modify and author some attribute that hides a group of poly faces on a prim? I tried visibility and displayOpacity, neither of them worked.

displayOpacity should work, but requires connecting it to opacity in a shader. It doesn't hide them but makes the faces have zero opacity.

I now realize that this question was nonsense, I was trying to do a boolean subtraction, but it wasn't working right. I now realize that the boolean messes with the usdxform attribute, so the geo modified by the boolean doesn't get the inverse transform before going back into LOPS, so copying the usdxform from somewhere above the boolean works as I expected. The same goes for things like solvers, which sometimes might freeze or delete the usdxform attribute.

jsmack
displayOpacity should work, but requires connecting it to opacity in a shader. It doesn't hide them but makes the faces have zero opacity.

great tip

Holeindices should work, if you want to hide faces at rendertime. Not the easiest thing to get up and running the first time tho.

Heileif
Holeindices should work, if you want to hide faces at rendertime. Not the easiest thing to get up and running the first time tho.

I'll look into this for sure.