wall techniques for foundry vtt maps

Walls in virtual tabletops

When playing on a virtual tabletop it is useful to be able to define what parts of it player characters can see, which includes map details and also other characters who might be there. Otherwise they can just see right across the whole thing and nothing is a surprise any more.

You can do this manually - hiding or revealing bits of the map, as well as tokens for other characters - but this can get a bit tiresome with a complex map. Or, you can set up walls on the map, virtual lines which block both vision and movement. That way, either GM or players can just move their character tokens around and the software automatically shows what they can and can't see, and blocks movement if they can't move into that square. Fancy. It can be a bit time-consuming to set the walls up, but you only need to do it once per map.

Here I'm using Foundry VTT which has a particularly sophisticated wall system. Other VTTs are available, with different degrees of support for walls.

The problem

Using a top-down map means that if you can't see through something, you can't see what it is either. Most of the time this doesn't matter because you set the wall to be in the middle of a wall or door:

so the player can then see half of that wall or door and it's clear what's happening:

The door icon there indicates to the player that that's an openable door. If this was the first time they'd ever been in the area they wouldn't see the faint image of the cabin behind the door, but I moved them in and out of it while doing the screenshots for this demo, and Foundry remembers what areas a character has seen and shows the player a dimmed version so they don't forget what was there.

However, if the map is large and pretty and you would lose a lot of the prettiness from using strictly top down walls, you need a way round that.

Wall types in Foundry VTT

Foundry has multiple options for walls - they can block light or not, they can block movement or not, they can even be openable and block hearing and have distance thresholds and all sorts of complicated things. Here however I only want to use three basic types of wall:

All of these also block movement.

The map I'm using

Here I'm using the Abandoned Tunnels map by 2minutetabletop - you can get it from that link for $1 or PWYW as well as many other fine maps and assets. (I subscribe to their Patreon so get these maps regularly plus Dungeondraft packs and tokens.) I like their hand drawn style a lot, and on this one you can see lots of lovely detail that it would be a shame to hide from the players, particularly around the rock walls and pillars. But, you know, they shouldn't just be able to see and walk through them.

The way I decided to do this was to define the space that players can move through using invisible walls and then define what they can actually see through with a combination of standard and terrain walls. (I could have used "ethereal" walls instead of standard ones as the invisible walls already enclose them, and this might actually save Foundry processing time when calculating movement, but I've done it now.)

Standard walls plus invisible walls

The cyan walls here are invisible and define boundaries through which character tokens cannot move. The light yellow ones are standard walls that block vision and movement. Here's what it looks like in wall editing mode:

and here's what the player would see (again, I've moved them around a bit beforehand so areas they've previously seen and now can't see are dimmed, but note that they will never have seen actually inside the rock pillars here so those are still black):

I've surrounded the rock slopes with invisible walls so that they can't be moved through, but they can be seen. An advantage of using invisible walls here is that I can be very sure as a GM which squares a player's token can move into and which they can't.

How does the player know where they can move?

They can't see invisible walls so you have to make sure that where you place them makes sense on the visible map. Or they could try to move their token into a square and it doesn't let them.

Standard walls plus invisible plus terrain

Here I'm using terrain walls (green) for some smaller pillars.

Because terrain walls only block vision on the second wall, the player can actually see the whole rock pillar, they just can't see what's on the other side.

Why not use terrain walls all the time?

• They don't work well with complex shapes - corners and protruding parts can result in strange results. They're best used with simple shapes like these.
• Because you can see all the way through something surrounded by terrain walls, just not out the other side, it reveals anything inside it. I mean that's the point. If there's something hidden inside it like a secret room, that would also be revealed, and you generally wouldn't want to give that away, or the fact that there wasn't anything hidden inside it. So they're best used for small objects on the map where that isn't going to be an issue.

Conclusion

You can use a combination of different wall properties in Foundry for some quite sophisticated effects; this is a relatively simple one compared to some of the things you can do. However it will take time to set them up.

For a quick map this probably isn't worth it, or if you have something better to do with your time, but you know what, sometimes I like just nerding out and drawing walls. This blog post took longer to write.