[RPG] In Roll20, how do you restrict PCs’ vision in situations like fog


For situations like Obscuring Mist and other vision impairment that overcomes Darkvision (and similar abilities), how have you successfully enforced that in Roll20?

My PCs would probably meta-game if they're simply told "you can't see in this area" and it kind of nullifies a major encounter coming up (and would be good to know for the future).

Assume Plus membership to the website (access to Advanced/Fog of War and Dynamic Lighting but not API).

Measurements of success:

  • Players are able to manipulate their token on a battle grid to explore the area of restricted sight
  • The GM can interrupt players when their sensory information changes without significantly interrupting play each round
    • Ideally, you would also avoid constantly moving them back
  • You have some method of providing information to players about what their character perceives
    • Ideally, only the player that "should" have the exact knowledge would have it, and others only what they can convey

Good answer(s) will follow the concept of Good Subjective and cover key points:

  • What has been your experience using the system?
    • i.e. player feedback, how you felt it worked
  • How you were able to restrict sight and also reveal information
    • Did you just tell the one player? Did everybody get to know when Bob was next to the bad guy?

Related question for physical play: For physical tabletop play, how do you restrict PCs' vision in situations like fog?

Best Answer

So I have not used Roll20 in a couple of years (or play D&D over those years unfortunately), but here is what I used to do for my players in situations where they were in the dark without a light (or otherwise had very low visibility). I would turn on Dynamic Lighting but turn off Global Illumination. Then for each of their tokens I would go to the advanced setting, make them emit light out to 5 ft and unselect All Players See Light. That way each player could see what was right next to them but would not see the other players if they were far apart. I also asked my players to not move too quickly (especially outside of combat when they are not taking turns) and they were pretty good at stopping or asking questions when they butted up against something or someone. Also you might try to incentives them asking questions in ways that do not reveal information to other players. "What am I seeing next to me?" instead of "IS THIS HIDEOUS CREATURE HOSTILE!?". In 5E they have ways to reward players for role playing well which could be adapted for this.

The disadvantage of this approach in your case is that if you only want small sections of the map not visible you will have to create a grid of light sources across the map and then turn off the ones where the Obscuring Mist should be.

That is what I have done in the past. Looking at the current offerings I think Advanced Fog of War is what you want. First of all, you can set the sight for each token (under the token's advanced settings):

tokens that emit light, or have a set view distance, clear fog dynamically as they're moved across the Page.

And they can only see what is in view for their token:

The fog cells that a token has revealed is saved for each token on a Page, so each player potentially can have a unique view of the same Page they are all currently exploring.

My suggestion would be to turn on advanced fog of war, set each token's sight to 5ft or however far you think they should be able to discern, use the Reveal Areas tool to reveal the whole map, and then use Hide Areas when something like Obscuring Mist is cast:

If you choose to reset the fog or manually hide areas, the areas within the Token's set sight or vision range can not be hidden from view.

Lastly, if the players need more than what they can see from the map when they uncover an area, I would "whisper" to that player. To help me be able to whisper fast enough I type up (in a text editor or word processor) whispers for things I know I want to share at some point. Then I can cut and paste them to the appropriate players. Of course the players are always going to ask about something that I have not prepared before hand, but hopefully these are not too frequent and all the players are patient while I type the answers to these questions.