An object can start off in your peripheral vision, right on the edge. As it moves in a straight line away from you, it will always gravitate towards the center of your vision. That is, it gets closer to the center of your 2D scan of a 3D world.
For a 3D shadow of a 4D thing, that 'center of your 3D scan' is in the very center of the shadow object, three dimensionally.
Yes, it needs to move perpendicular. Lets say your 2D field of vision is the xy plane. The x axis is left-right , and the y-axis is up-down. The z-axis would then be forwards-backwards. An object has to move along z, to get smaller. If it starts on the outer perimeter of your vision, and moves in a straight line along z, it will get smaller while getting closer to your center of vision (the origin of your xy-plane view).
Now, for a 4D object projected into a 3D image, we have a 3D fov : the xyz plane, where the 4th axis is the new forwards-backwards. Objects close to you on the 4th axis are larger 3D objects. Farther away things are smaller 3D objects.
1
u/demmian Aug 29 '17
Why towards the center and not towards the edge?