Ok. So this is actually both a simple question to answer and a complex one.
Animation is not “2D” but is a “2D representation.” There is depth- pencil, pen, carving, paint, ink, even the particles that make up a “2D” screen have depth no matter how small (so yes, even a computer generated “2D” image on a screen or projection is “3D” because it has at least 3 dimensions we could measure…)
That said- within a 2D representation, the portrayal of animation or pictures is also a 2D representation. It may or may not be detailed to add the optical effect of a third dimensional existence such as shading etc- but ultimately it is a 2D representation even if that is a 2D representation of a 3D object. So if you somehow magically existed in that world suddenly, shadows wouldn’t be shadows, they’d just be patches of black. Faces would be flat and just have darker spots etc. that might give the appearance of depth, but everything would be “flat.” If we start to discuss meta physics of existing..
.. in a space like that it can get messy and would largely all be theoretical- and we don’t have a frame of reference for how life forms that evolved or existed in such an environment would perceive things like light or their environment, movement etc. That’s it’s own tangent- but without exploring that the closest analog assuming things are similar is that looking at animation from the POV of an animated character would be the same as looking at a 2D representation- so basically not different than you watching a play or looking at an object in front of you. Just the same as you looking at the screen, context and art style are basically the only things that distinguish within a 2D representation what is “real” to that 2D represented world and what is a “picture” or “animation” etc. so looking at a “TV” would be the same as just watching a play through a TV shaped cut out basically.
“1D,” or more specifically to the point here- a “1D representation” is essentially an odd sort of…. dot. It’s a single point of information that has only a single dimension that is measurable.
So in “2D representation” we have an “X” and “Y” axis- things can have height and they can have width but they cannot have depth. In a “3D” representation things have depth as well- so a computer graphic where an object ACTUALLY has depth vs. a drawing where optical tricks are used to make it appear it has depth is an example.
A “1D” representation has only one of those dimensions. It might have height but have no width or depth. You could really only see a “1D” object, if at all, from very specific vantage or specific conditions if viewing.
So if you had a computer generated animation, a claymation or puppet etc that was “3D,” and it was watching “2D” animation or viewing a “2D” image- that would in essence be no different than you or I watching a cartoon or looking at a picture. A “2D” character watching a “1D” image- you probably couldn’t see they were looking at at anything and if they could “see,” they probably also couldn’t get any useful viewing or observation from a “1D” object.
Animation is not “2D” but is a “2D representation.” There is depth- pencil, pen, carving, paint, ink, even the particles that make up a “2D” screen have depth no matter how small (so yes, even a computer generated “2D” image on a screen or projection is “3D” because it has at least 3 dimensions we could measure…)
That said- within a 2D representation, the portrayal of animation or pictures is also a 2D representation. It may or may not be detailed to add the optical effect of a third dimensional existence such as shading etc- but ultimately it is a 2D representation even if that is a 2D representation of a 3D object. So if you somehow magically existed in that world suddenly, shadows wouldn’t be shadows, they’d just be patches of black. Faces would be flat and just have darker spots etc. that might give the appearance of depth, but everything would be “flat.” If we start to discuss meta physics of existing..
So in “2D representation” we have an “X” and “Y” axis- things can have height and they can have width but they cannot have depth. In a “3D” representation things have depth as well- so a computer graphic where an object ACTUALLY has depth vs. a drawing where optical tricks are used to make it appear it has depth is an example.
A “1D” representation has only one of those dimensions. It might have height but have no width or depth. You could really only see a “1D” object, if at all, from very specific vantage or specific conditions if viewing.