Anticrepuscular rays are essentially parallel, but appear to converge toward the antisolar point, the vanishing point, due to a visual illusion from linear perspective.
[2][3] Anticrepuscular rays are most frequently visible around dawn or dusk.
[4] A common example of a single anticrepuscular ray is provided by the shadow of a mountain at sunset, when viewed from the summit.
It appears to be triangular, whatever the shape of the mountain, with the apex at the antisolar point.
[4] Media related to Anticrepuscular rays at Wikimedia Commons