Objects look stretched out/distorted only around edges of screen

Question

Is this an FOV issue with my perspective camera? In my scene, spheres look like eggs/oval shaped rather than spheres when they reach the edges of the screen. Anyone know why this happens?

Answer 1

It sounds like you've encountered one of the unfortunate realities of 3D.

In any 3-dimensional scene, the view from a given point is most naturally thought of as a sphere. When we render a scene, we're rendering a piece of that sphere, but we need to somehow convert that piece of a sphere into a flat rectangle, since our computer screens are flat, not round.

So, in order to render a 3D scene as a rectangle, the software needs to use a projection. For 3D rendering, the most common projection is probably a rectilinear projection, also called a gnomonic projection. (On Wikipedia, see "Rectilinear lens" for a discussion of rectilinear projections in photography, and "Gnomonic projection" for a discussion of rectilinear projections in mapmaking.)

The biggest advantage of a rectilinear projection is that straight lines in the scene appear as straight lines in the rendering. A big disadvantage is that objects far from the center are distorted: small circles get turned into large ovals.

This phenomenon is an unalterable mathematical fact that no software will ever be able to overcome. However, there are things you may be able to do to mitigate the situation. One option is to use a narrower field of view. Another option is to use a different projection; the answers here have a few suggestions for how to do that: Three.js - Fisheye effect