We are about to start a new campaign and I thought it would be fun to use Proficiency Dice (DMG, p. 263) instead of static proficiency bonuses. I discussed it with the players and everyone agreed that it could add a nice dynamic to the game. One of the first questions that came up though that I can't seem to find an answer for is how to handle passive perception? Obviously if they aren't proficient in perception it doesn't matter, but I have a few characters who are.
So how do I handle passive perception when using proficiency dice?