# Prismatic wall is described as vertical. A cylinder has vertical walls. So can a Prismatic wall be shaped as a cylinder?

Prismatic wall is described as vertical. A cylinder has vertical walls. So can a Prismatic wall be shaped as a cylinder?

The point is that a cylinder height is vertical, not oblique, not horizontal.

## The wall is a flat plane

There is no explicit statement on this, but it is likely that the wall has to be a planar, straight form. The spell says:

Prismatic wall creates a vertical, opaque wall—a shimmering, multicolored plane of light

and plane in this context in the dictionary is defined as

"a flat surface on which a straight line joining any two points on it would wholly lie"

So the wall is a flat surface on which straight, not a circular lines would fit in any direction.

As a second point of evidence, the wall also says

The wall’s maximum proportions are 4 feet wide per caster level and 2 feet high per caster level

The width would not make sense if it was cylindrical, which creates a closed loop (or you would be looking at a cylinder 4 feet wide per caster level, creating a much larger surface, clearly not what is intended.)

This is also in line with most other wall spells, that also create a flat plane, for example wall of ice, wall of iron, or wall of force. For an example how language creating a cylinder would look like, you can look at the spell magic circle, which says "You create a 10-foot-radius, 20-foot-tall cylinder of magical energy."

• I think the assumption would have to be that if the wall was allowed take a form other than the traditional 'flat' plane (en.wikipedia.org/wiki/Plane_curve) the width would be the length of the top edge, making it the circumference of the cylinder rather than the width. ie: a cylindrical wall would have a diameter (nominally "width") of 4*CL/pi Commented Dec 19, 2023 at 22:09
• The surface of a cylinder is flat in the proper geometric sense of the word. Commented Dec 20, 2023 at 4:57
• It’s isometric to a plane :P Commented Dec 20, 2023 at 5:00
• @ThomasMarkov :-). I think the difference of how a mathemtatician uses these terms compared to what they mean in the game's common English usage is why both the dictionary writers and this answer had to be careful to describe what the plane is with the help of straight lines. Commented Dec 20, 2023 at 5:04
• For non-math readers, I believe what Thomas is saying when he says plane and cylinder are isometric is that they are not the same thing, but a plane could be transformed into a cylinder (rolling it up so to speak) or vice versa, while preserving distances between all points (except, I guess if you measure across the "cutline" on the cylinder, because that would lead to a second, shorter distance between those points). Commented Dec 20, 2023 at 12:03