A shadow is not the same as a line drawn by a pencil. And a 2d line can be for example the contrast of two colours, the “line” that delimits an object from your perspective - these are no drawn lines with any width, they are not there as full 3d objects. I would think a shadow is a similar case, just as a film projection. It has no thickness.
Well shadows are the absence of light, so defining them is a little weird, but they exist the entire distance from where the light source is interrupted to where they are projected on, same with projections, it’s not just what’s on the screen, but the light the whole way to the screen.
Even ignoring that, the surface that a projection lands on has texture and depth.
A shadow is not the same as a line drawn by a pencil. And a 2d line can be for example the contrast of two colours, the “line” that delimits an object from your perspective - these are no drawn lines with any width, they are not there as full 3d objects. I would think a shadow is a similar case, just as a film projection. It has no thickness.
Well shadows are the absence of light, so defining them is a little weird, but they exist the entire distance from where the light source is interrupted to where they are projected on, same with projections, it’s not just what’s on the screen, but the light the whole way to the screen.
Even ignoring that, the surface that a projection lands on has texture and depth.
A shadow is a 2d projection of a 3d object projected back onto 3d space.