hmm.. I wonder which face (ABCD or EFGH) should be in front and which in the back. If we are projecting, some of the lines in the back should not shown right?
Good question! This is a wireframe representation of a cube, i.e., the visualization of a 3D model where only points and lines are represented. Clearly, if this cube were opaque, then some of these lines would be hidden.
So which face is in the back: ABCD or EFGH? Well, we defined all faces of the cube to have the same surface area. Yet, after perspective projection, one of these faces appears to be smaller than the other. Could this bit of information tell us which face is further away? This slide on perspective projection might have a hint.
I'm used to seeing orthographic and isometric perspective in 3D modeling, so I was wondering, where would a perspective projection would show up in applications? Or why would we choose that to use that over other projections?
Perspective projections shows up when trying to simulate the way that we experience our 3D world, and gives a sense of depth/distance. Perspective projection is used in video games (e.g., first-person shooters) or films, for example. One of the key differences is that, in perspective projection, objects appear smaller when positioned further away from a camera; for orthographic/isometric perspectives, the size of the objects remain the same regardless of how far they are from a camera.
How many activities like this can we expect for the rest of the class? I think it's super fun!
We'll see if we can squeeze in a few more interactive activities. :-)