Some objects are not rendered in UV pass I created the sea and floating object - the ship's hull. The ship floats in the sea, using the method from this tutorial - https://www.youtube.com/watch?v=11F1NRpqrzY (dinamic paint).

Then I modeled the mast with sails, flags and ropes in another scene, and also modeled there a new hull, slightly modified, but almost the same. 

I had to attach the structure (the mast, etc.) to the floating object (old hull of the ship), so that the structure repeats it movement.

I used parenting.

I transferred this structure with the mast and etc. to the first scene and parent it to the old hull of the ship. Then I moved it so that the new ship hull was in the same place that the old hull. Then I made the old hull invisible.

Then I noticed that the sail is shifting towards during the animation, so I delete the old Parenting of the sail and Parent sail to the mast.

Everything was ok. https://www.youtube.com/watch?v=65cdCvsL7pU

But when I export MultiLayer EXR, in UV pass the ship's hull and sail are black, looks like they are not used in the creation of UV pass. 


Why is this happening and how to fix it?
Thanks in advance!
The UV pass display the UV coordinate from the UVmap so if an object don't have one they will be black, to solve this you have to unwrap these objects and render again.