Let's ignore the mainstream-science explanation for crepuscular rays with light-scattering and perspective.

https://en.wikipedia.org/wiki/Crepuscular_raysLet us ignore that. Let's instead assume that what we see with our unaided eyes were true: That the rays emanate DIRECTLY from a light-source.

**You cannot use the angles of the crepuscular rays to deduce the position of the Sun, because you don't know how far away the cloud is. **

A simple experiment to demonstrate my geometric argument:

Shine a light on a wall. In front of the light hold a piece of paper, so you can see its shadow. (Or just hold a paper in front of your face and squint your eyes.) Hold the paper in such a way that a corner points up.

If you hold the paper upright, the shadow of the corner has the same angle as the corner. 90°

Now, as you tilt the paper, the angle of the shadow of the corner gets bigger and bigger than 90°, even though the corner still has 90°.

**My point is:** What you see in the crepuscular rays is not an upright triangle. You see a tilted triangle and you have no idea how far away the top corner is. From the crepuscular rays you could deduce the vector from the position of your eye to the position of the source of light, but you don't know where on that line the source of light is.

Now, if we were to triangulate the directions of crepuscular rays from several positions on Earth,

**THEN** we could calculate where the top corner of the triangle is, but a single observer cannot measure the tilt of the triangle. He sees only the projection of the triangle.

Therefore, observing crepuscular rays as shown in the image above is no proof for the distance of the Sun or for Flat Earth.