Saturn's rings

[mark_aldred]

Hi

I'm looking for ideas to solve a problem I'm having with Saturn's rings. The rings are a two-sided mesh with no thickness.
It's fine when the light source is above or below the plane of the rings, but of course when the light is parallel no illumination hits the mesh and the rings go dark.

Ideally, the rings would be illuminated most when the angle of incidence is the greatest, then would become only slightly darker as the angle narrowed but stay at a minimum as the light source crosses the plane.
It would also be ok for the rings to remain a constant brightness.

Any ideas?

[fixeighted]

A thin spline around the edge with a self illuminated mat will do what you need most likely.

[mark_aldred]

A thin spline around the edge with a self illuminated mat will do what you need most likely.

Thanks.
I need to retain the shadow cast by Saturn. Anything that illuminates the whole ring system is going to affect that unfortunately.

[fixeighted]

No, I just meant the self-illum on the spline only, as here...but maybe I misunderstood.

[fixeighted]

Actually, if you did use a copy of the ramp used for the rings as a e.g. 10% self illumination, it has the side effect of showing the top shadowing when viewed from the bottom...which may
or may not be correct but seems right to me.

[mark_aldred]

No, I just meant the self-illum on the spline only, as here...but maybe I misunderstood.

Ah, I think I see. I don't mean the rings being visible edge-on.
If you look at that image and imagine that the camera remains fixed, but the light moves down and crosses the plane of the rings.
The angle of incidence of the light becomes zero when the light is parallel to the plane and the rings are no longer illuminated.

What I did before was bake the shadow and composite the result onto fully illuminated rings. It worked, but I'm looking for a better one-shot solution.

[fixeighted]

Ah I see what you mean now.
How about this approach then?

[mark_aldred]

Actually, if you did use a copy of the ramp used for the rings as a e.g. 10% self illumination, it has the side effect of showing the top shadowing when viewed from the bottom...which may
or may not be correct but seems right to me.

Unfortunately the shadow cast by Saturn disappears with the illumination. Even if I give the rings self-illumination, it still disappears. The shadow needs to appear when the rings are illuminated from the opposite side too.
It feels as if there should be a solution with translucency and/or composite maps, but I'm having trouble getting there.

Thanks. I appreciate the help.

[fixeighted]

After a little further investigation, I think this seems to do what you want.
I was missing the uniformity in the previous, plus it lacked the shadow when edge-on.
This version uses a fastsss shader with same ramp for colour, sss and opacity, with radius to suit and set to raytraced solid.

[mark_aldred]

After a little further investigation, I think this seems to do what you want.
I was missing the uniformity in the previous, plus it lacked the shadow when edge-on.
This version uses a fastsss shader with same ramp for colour, sss and opacity, with radius to suit and set to raytraced solid.

Thank you! Outstanding!!
I was getting streaks along the direction of illumination with the light parallel to the ring plane, but deleting the ring edge polys seems to have fixed it.

Thanks for the help!

[fixeighted]

Hehe...good stuff...got there in the end
It satisfied my 'hangover challenge' for today also

[mark_aldred]

Sorry to resurrect this thread, but when I added stars to the scene I found I have a problem. In the below image, you can see that the rings are completely transparent in shadow. What I would like is for them to occlude the stars a little. Ideally, I'd use a Falloff map set on Shadow/Light as a mask and just add another map or material in the shadow, but that's not possbile.

Any ideas?

[fixeighted]

Not sure how you have yours eventually setup but this is the result I get.
Is it possible you have too much grey in your opacity map, which with the rings being so thin, looks like it's transparent in the shadow?
Also may be the sss radius that needs tweaking to solidify the rings a bit more.

[mark_aldred]

Not sure how you have yours eventually setup but this is the result I get.
Is it possible you have too much grey in your opacity map, which with the rings being so thin, looks like it's transparent in the shadow?
Also may be the sss radius that needs tweaking to solidify the rings a bit more.

Man, I'm an idiot. I still had the Output Amount on the opacity bitmap set to 0.5 from the last material I used.
Panic over.

Thanks

[fixeighted]

Hehe, nice and simple fix then