Yet again, we inherit the ambiguous wording from 3rd edition.
From the playtest rulebook, p. 198:
WALLS
Some spells create walls. Each spell lists the depth, length, and height of the wall, and specifies how it can be positioned. Some walls can be shaped, meaning that you can manipulate the wall’s shape into a form other than a straight line, choosing its path square by square. Each square of the wall’s length must be adjacent with the square or squares next to it, so walls cannot be shaped to make a diagonal line. The path of a wall can’t cover the same space more than once, but it can double back so one section is adjacent to another section of the wall.
Can someone explain what "walls cannot be shaped to make a diagonal line" means? Does this mean from the corner of one square to the corner of another square diagonal to the first? Does this mean from the centre of one square to the centre of another square diagonal to the first?
Let's look at specific wording of some wall spells to see what they say.
From the playtest rulebook, p. 269:
WALL OF FORCE
SPELL 6
Casting Material Casting, Somatic Casting, Verbal Casting
Range 30 feet
Duration 1 minute
You form an invisible wall of pure magical force up to 50 feet across and up to 20 feet high. The wall has no discernible thickness. If the wall’s surface would be broken by any creature or object, the spell is lost. The wall has AC 10, TAC 6, and Hardness 23, and it can take 3 additional Dents before being broken. If the wall is broken, the spell ends. The wall blocks physical effects from passing through it, and because it’s made of force, it blocks incorporeal and ethereal creatures as well. Teleportation effects can pass through the barrier, as can visual effects (since the wall is invisible). Wall of force is immune to dispelling effects of its level or lower, but the wall is automatically destroyed by a disintegrate spell of any level or by contact with a sphere of annihilation or rod of cancellation.
Heightened (+2) The Hardness of the wall increases by 5
Here we have a classic, the Wall of Force. Per the spell description, there's no shaping, no thickness, and no information about targeting the spell.
So, let's go to the rules for targeting spells, and see if they can shed some light on this topic!
The playtest rulebook, p. 196, gives rules for ranges, areas and targets. There's no indication here how to target wall spells.
The playtest rulebook, p. 298 gives area diagrams for an aura, burst, cone or line. The description of areas on p. 299 lists areas for an aura, burst, cone, or line. There's no indication here how to target wall spells. (Note specifically that line spells are distinct from wall spells, in that they are legally allowed to go diagonally per the chart on p. 298.)
So, here's the hypothetical scenario:
Ezren the wizard finds himself adjacent to a red dragon. Feeling this situation is rather undesirable, he spends his turn using 3 actions to cast Wall of Force to create an invisible, impenetrable barrier between himself and the dragon, blocking its breath weapon, attacks and line of effect for spells.
However, Ezren has no squares between himself and the dragon, being directly adjacent to it. Is the Wall of Force created on the grid line between the two creatures, or is a full empty 5 ft. square needed between both creatures to allow the spell to be created, since the wall cannot be broken by a creature or object?
Yeah I'm scratching my head on walls as well.
Some of them actually give you additional options in the descriptions, but clearer definition of the basic wall would be appreciated.
True diagonals would leave open spaces. You basically have to zig-zag them.
--x
-xx
xx
vs
--x
-x
x
Seems to me it'd be perfectly logical to create a wall on the diagonal by using the same rules for distance as you would movement.
So a 50 ft. wall would cover 6 diagonal squares (45 ft.) and because you're on the diagonal you accept that you lose 5 feet to shift it.
Granted I know there are some people that would have a fit over losing a precious five feet but it'd not be hard to adjust the description to say something along the lines of "any additional distance that cannot cover the full amount of the diagonal is lost/wasted".
Between me and a dragon, I'd take that 45 ft.