Shadow of moon on host planet

[papics]

It would be great, and possibly not too difficult to implement, to have the shadow of different moons show up on their host planets if the planetary alignment is appropriate, just like it happens in real life at many places of the Solar system. This is the most interesting on Jupiter, and could be similarly nice on Jool!

[tntristan12]

It's not as trivial as you make it sound. I'm not that familiar with the details, but I've seen it mentioned before. Would be nice though, and might happen some day. I hope somebody can explain better than I can what'd be required for this to work.

[Vostok]

in addition to this, it would be nice if planets cast shadows on themselves, something that doesn't currently happen, leading to some funny lighting around the edges.

[technicalfool]

It's not as trivial as you make it sound. I'm not that familiar with the details, but I've seen it mentioned before. Would be nice though, and might happen some day. I hope somebody can explain better than I can what'd be required for this to work.

Would this help?

(Courtesy of wikimedia)

Basically, you would need to cast a double-cone back from the planet to act as the Umbra/Antumbra, and another blunted cone for the penumbra. Or two double-cones, as shown in the diagram. Pixel shaders could potentially be used to then paint the relevant black or grey circles on any moons passing through the cones. I've suggested this a while back, and got told that this was apparently attempted and then abandoned (for now) as being too intensive an operation.

That said, I do think it would be pretty awesome to have. Maybe there's some way to cheese the effect with a "planet is X radius and Y distance away, grey and black circle should be W and X in size and U and V in intensity". Spacecraft are already affected by being in the umbra (0.19, wasn't it?), so who knows?

Edited August 31, 2013 by technicalfool

[RocketPilot573]

This would make eclipses far more interesting!

[technicalfool]

And here is the original thread.