Author Topic: Planetary rings from default shader?  (Read 1207 times)


Offline TheBadger

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Re: Planetary rings from default shader?
« Reply #16 on: February 05, 2017, 01:10:45 AM »
Oh man, I just read that thread. Now I miss Jo  :(
It has been eaten.

Offline N-drju

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Re: Planetary rings from default shader?
« Reply #17 on: February 05, 2017, 08:58:10 AM »
From my trials I can see that painting a disc object just with PF is sometimes sufficient to have a nice looking planetary rings... if you look at them from a significant distance of another planet's surface. Something I'm doing right now.

Populating stones or rocks on discs is probably more realistic but from large distance it looks patchy and the ring lines are getting blurry and sparse. Colorful disc object with just a touch of luminosity (about 0.014) is not perfect but not too bad either. More RAM friendly too obviously... Even if stones in population are 25000 meters apart it eats up your memory real good.

Just my two cents. But obviously there are many methods. All of them equally good I'd say. :) Though some do not allow you to rotate rings freely like Badger said. At least not easily...
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Offline Ogre

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Offline billhd

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Re: Planetary rings from default shader?
« Reply #19 on: May 19, 2017, 02:06:46 AM »
I haven't been active but recently looked at this interesting thread.  I had done some experimenting with using fake stones on discs.  The trouble with discs is that the varying density of stones does not cast as ring shadows on the planet, the disc seems to be a one-way object with impinging light and wants to only cast a single shadow.  From this perspective you can't get "under" the rings and look up through them either.  This is from a while back so I had to look in the file to see that I used a glass shader on the disc to get transparency.  Trig functions make the ring structure as masks for the fake stones. Since I couldn't get proper shadows from the various stone densities I faked it with a few discs and soft shadows.  See pic.  I like Mr. Fraser's approach since he gets the explicit shadows on the planet and can get close up to the constituent particles.  But I like fake stones because you don't have to populate, they are fast.   By coincidence, I had recently thought to use a distance shader limited atmosphere for rings, but could not get the distance shaders to limit the atmosphere to a thin slice, and have had only primitive success with the cloud approach when that failed (was trying to apply the trig functions but it seems they don't map to the cloud slice the way they map to the discs). 

As an aside, real planetary rings look different from top or bottom with respect to the sunlit side because different particle/chunk sizes have different forward and backward light scattering properties.   -Bill

Offline Dune

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Re: Planetary rings from default shader?
« Reply #20 on: May 19, 2017, 05:17:31 AM »
Interesting and a very convincing result! Strange that the fake stones don't make shadows, even if you set the disc object as 'do shadows'? Did you try 2 disc objects, one rotated 180, both with same fake stones distribution? In that case you may not need the lateral displacement of the stones. Really don't know if that would work.
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Offline billhd

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Re: Planetary rings from default shader?
« Reply #21 on: May 19, 2017, 05:03:01 PM »
Thanks Ulco, Kind words from a master.  I attached a simplified setup.  I was incorrect in recalling the "under rings" effect, there is indeed a transparency result - see the two renders from the attached tgd.  But even deleting the fake stones leaves a solid shadow of a transparent ring.  I also tried checking ray tracing options in the disc and render dialogs.    Even with this limitation, I think the technique can yield some satisfying results with fast render times.  If you or anyone else sees to exploring this shadow issue I would be keenly interested in any insight.

Offline Dune

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Re: Planetary rings from default shader?
« Reply #22 on: May 20, 2017, 07:53:51 AM »
I've done a little experimenting on a small scale (3m planet), but the problem remains the disc shadow. With glass shader, or default shader as in this screendump, I can't get rid of that full shadow.
Maybe Matt can add some function to make the opacity of the default shader work on shadows of the object too. I don't know if an imported disc will do the same, I'll try.
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Offline Hannes

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Re: Planetary rings from default shader?
« Reply #23 on: May 20, 2017, 12:32:01 PM »
As far as I remember the fake stones are just some sort of displacement, no objects, so I guess it would be difficult to get shadows only from the "stones". Maybe some masking using the fake stones shader would work??

Offline billhd

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Re: Planetary rings from default shader?
« Reply #24 on: May 20, 2017, 04:04:53 PM »
Thanks Dune and Hannes for looking, my understanding is that the fake stones are mesh displacements. I was thinking that a planar distance shader that masked the plane of the disc but not the stone displacements, but for a little vertical extent near the disc, could work, but have not tried it yet.  This would work for viewing from the stone-top direction.  I'll get to trying that reasonably soon.

Offline Dune

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Re: Planetary rings from default shader?
« Reply #25 on: May 20, 2017, 04:23:17 PM »
It works if you use an imported disc and forced displacement. Check out my Planetary Rings thread.
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Offline billhd

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Re: Planetary rings from default shader?
« Reply #26 on: May 22, 2017, 07:31:45 AM »
Thanks, I had missed that.  Currently having difficulty seeing my imported disc but will eventually get it; have scaled, translated etc.

Online bobbystahr

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Re: Planetary rings from default shader?
« Reply #27 on: May 23, 2017, 05:21:25 PM »
Thanks, I had missed that.  Currently having difficulty seeing my imported disc but will eventually get it; have scaled, translated etc.

Did you run it through PoseRay before importing it into TG? That's often helpful.
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Offline billhd

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Re: Planetary rings from default shader?
« Reply #28 on: June 12, 2017, 08:47:35 PM »
Thank you Bob, I currently only have a mac so I cannot run poseray.  Perhaps in the next 6-12 months I will expand to both operating systems.  Appreciate your suggestion.

Offline N-drju

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Re: Planetary rings from default shader?
« Reply #29 on: June 13, 2017, 07:13:17 AM »
It all actually depends on what you are after. If for instance you just want planetary discs from the surface of another planet (and light not poking through the discs) all you really need is a colored disc object. Good for far away shots. It's no use to complicate matters when not necessary.
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