How much starlight reaches point (on or above the planet) through its
ring system — the product of (1 − opacity) over every band the ray to
the star crosses. ringNormal is the ring plane's unit normal (through
the planet's centre, the origin of this frame).
Band edges are softened by the star's own angular size times the
distance to the crossing, which is the real width of the penumbra a
ring edge casts — the Cassini Division's shadow on Saturn has soft edges
for the same reason a moon's does. A ray parallel to the plane (the
planet's equinox) or one that crosses it behind the star direction casts
no ring shadow: rings have essentially no thickness.
How much starlight reaches
point(on or above the planet) through its ring system — the product of (1 − opacity) over every band the ray to the star crosses.ringNormalis the ring plane's unit normal (through the planet's centre, the origin of this frame).Band edges are softened by the star's own angular size times the distance to the crossing, which is the real width of the penumbra a ring edge casts — the Cassini Division's shadow on Saturn has soft edges for the same reason a moon's does. A ray parallel to the plane (the planet's equinox) or one that crosses it behind the star direction casts no ring shadow: rings have essentially no thickness.