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I've noticed that when it's the equinox on this planet I'm making, the sun seems to cast a double shadow on the planet. How come the planet's ring seems to make two shadows with a space in between, instead of one "line" shadow. Is this accurate to real life, or a quirk of the rendering engine I'm using?

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    $\begingroup$ That would look more like a quirk in the engine you are using. Presumably, if you're using some light scattering technique, your sharp edges generate a high photon scattering opacity, but this is off-topic here. $\endgroup$
    – AtmosphericPrisonEscape
    Feb 23, 2020 at 16:29
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    $\begingroup$ I recommend checking out the Cassini raw images (the filters are your friends). I do a bit of space-photography-esque rendering and photo-editing, and it's a gold mine! It's also fun to browse for the marvel of it all. $\endgroup$
    – BMF
    Feb 24, 2020 at 22:27
  • $\begingroup$ Thanks for the link! $\endgroup$
    – Andrej Butić
    Feb 28, 2020 at 9:17

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This might happen if you model the ring as opaque but of very little thickness and in the same plane as the vector between the planet and the sun Seen edge on from the equator, the ring would block none of the sun's light, but from a little north or south of the equator, the ring would block more of one hemisphere of the sun.

So I would check first if your geometry has things lined up too perfectly before considering a fault in the rendering engine.

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  • $\begingroup$ Yeah, this is basically the planet at equinox, when i render it slightly later in its orbit, there is only one, normal shadow, in one hemisphere. The ring is also opaque, with very little thickness, as you said. $\endgroup$
    – Andrej Butić
    Feb 28, 2020 at 9:17
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The pattern is possible if there is a very large gap between two rings. Based on the spacing of the shadows, the gap would be at least as wide as a ring.

If there is only one ring, then it likely is a quirk of the engine.

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The shadow cast by the rings onto Saturn is much more pronounced as shown by the Cassini spacecraft (e.g. here). Mind also, that the shadow is comparatively sharper than on Earth as the sun's apparent diameter is smaller at the ring planets' distance.

And, of course, the intensity of the shadow depends on the density of the rings - and the obliquity of the rings wrt light direction; they are extremely thin, and not very much packed with material, yet when you look through them nearly radially, they still block most if not all light.

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It is very possible.

The intensity of the shadow depends on the density of the rings - and the obliquity of the rings wrt light direction; they are extremely thin, and not very much packed with material, yet when you look through them nearly.

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