Many people are confused by Crepuscular rays because they APPEAR to converge at a point "just behind the clouds". But really they are (nearly) parallel to each other and it's just perspective that causes this appearance (as I will show).
My video below shows crepuscular rays from a rapidly moving vehicle - if the *apparent* spray of the rays was merely caused by the sun being Near to the clouds the relative angles of the rays wouldn't change as the car moves -- they would remain spraying to the left or to the right.
However, you can clearly see the "depth" of the rays as closer rays move across the field of view more rapidly than further rays and these closer rays completely flip from left-spray to right-spray. The reason for this is that the Sun is very distant, all the rays are actually parallel and are coming in at an angle towards the viewer, and because of this angle only appear to converge due to perspective effects (exactly as train tracks appear to converge in the distance but are clearly parallel).
Our eyes are not used to evaluating ephemeral rays in 3-space with such complexity - but hopefully this view helps you to see and understand what the shape of that 3 dimensional volume really is (tilted rays that only appear to converge).
If we could simply trace the apparent 'sunbeams' to their source then you would have to conclude from the following image that the sun goes down below the surface of the Earth.
So this is clearly a nonsensical approach to resolving what we see.
So clearly this is an absurd methodology to use to determine what we are seeing.
Do the bottoms of these buildings converge or are they parallel?
This model is from the SketchUp warehouse and I just set up a few views to take some screenshots.
It sure LOOKS like our rays converge!
But they don't.