The Solar System: September, AD 15605

[töff]

You guys think I have forgotten this, huh. I have NOT! I just ain't worked on it, being all swamped etc. I reallllllllly want get back to this and finish it in time to include it in my little magazine, with the last chapter of the Tour Of The Solar System.

Speaking of which ... I just shipped the 3rd of the 5 chapters. Has anybody read any of it?

1 Titan http://links.mysteryandmagic.com/Dar..._One_Titan.pdf
2 Rings http://links.mysteryandmagic.com/Dar..._Of_Saturn.pdf
3 Io http://links.mysteryandmagic.com/Dar...sion_Klish.pdf
4 Ceres [working!]
5 Mars [working!]

[töff]

Planetary Rings

When last I left off, I think I was working on the planetary rings. Recently I took two good-sized steps forward on this little map project.

First, I realized that ring systems change significantly over time. This is 13,000 years in the future, so I do not have to match the current appearances of the ring systems of Jupiter, Saturn, Uranus, and Neptune. I will match Saturn's, though, because it is familiar and characteristic to modern viewers ... and, plus, I already have a bitmap for the color & transparency ... but, yay, I don't have to find actual accurate bitmaps for the others. I can just wonk them up in Photoshop. That's gonna save time & number-crunching!

Second, I had a method for converting the color & xpncy maps into radils (rings) for rendering, but I since developed a better method, inspired by an offhand comment on some old newsgroup. Anyway, here's how I am gonna make rings.

=== PROCEDURE ===

You have to have color & xpncy maps for your rings. I don't remember where I found Saturn's color map on the web, but it was out there. The map has to be scaled from the center of the planet out to however far a radius you want the rings to be visible to. In my map, it worked out to 9,000 pixels, nice high resolution. The bitmap only has to be, I guess, in theory, one pixel high, but I'm scared of single pixels so I cropped it to 10 pixels high. Call me crazy.

(The sizes screw up embedding the images on this page, so I will just put links ...)
http://links.mysteryandmagic.com/rings/07_Saturn.jpg
http://links.mysteryandmagic.com/rin...Ring_Color.jpg
http://links.mysteryandmagic.com/rin...Ring_Xpncy.jpg
http://links.mysteryandmagic.com/rin...y_Brighter.jpg

Next, fire up your 3D app, which if it ain't http://autodesk.com/3dsmax then maybe this procedure won't work. Awesome software -- high learning curve, monstrous price tag, some funny quirks, but awesome. End plug, and no I don't work for them. Anyway ...

1) Start with a sphere. The radius should be the edge of the ring system as measured from the center of the planet.



2) Make a material with your two bitmaps: diffuse color from your color bitmap, and transparency (opacity, whatever your app calls it) from your transparency bitmap. ... Notice that the color bitmap for Saturn has black where there's no rings, because there's no color there, of course. This tends to darken the rings overall, which I compensated for by brightening the xpncy bitmap. It'd probably work better (or be more accurate, anyway) if I brightened the color bitmap or just used a nice pale tan/orange/beig stripy color bitmap without any black in it at all, because the xpncy bitmap is where you really want your "empty space" data. But whatever, this works fine. Do NOT add ambient/self-color to the material, if you want the planet to cast a shadow on the rings (which you do want, trust me).



3) Apply the material to the sphere using a PLANAR uvw map.



4) Depending on your geometry, you might need to rotate the uvw map. You want it on the top of the sphere.



5) Like an infinite god, smash the sphere down flat to zero vertical dimensionality.



6) Stick your planet in the middle (this one's not to scale), add a sun light and some stars in the backdrop, and render!





So now I'm off to make some ring-system bitmaps for the other gas giants ... and then I can move on to some new part of this sprawling project!

[RPMiller]

That is really sweet! Thank you for the tutorial.

[Redrobes]

Thats cool - nice pic at end too.

Interesting refresher on the old scale astro problem. Did you catch my silly vid about real planet scale in our system...
http://www.cartographersguild.com/showthread.php?t=4567

I don't recommend anyone doing anything bigger than a planet and immediate satellites of at a real scale.

[töff]

Don't talk to me about scale ... It's been the largest spear in my side for doing a map of The LATTICE.

[Steel General]

That looks really good.

[töff]

Crap, the bitmaps distort by the sine, though. Crap.

Hmm.

And it was such a wonderful, easy method! ... lol ....

[töff]

w00t, I can correct for the trigonometric distortion, yay!

Cripes, that was kinda like Hubble being nearsighted. Remember that?

I guess I need to redo that microtute.

[töff]

Well, instead of redo the whole thing, I can just show the procedure for fixing the distortion. It's simple & short.

1. Here's the problem. The view of the linear bitmap gets distorted when wrapped from pole to equator. The further we get to the edges, the more it shrinks. (Damn spherical geometry!) We want some space for the planet (and between planet & rings); that's black ... then we want three equal-sized rings: blue, red, and outer green.





2. Here's the solution. First, reverse the direction of the bitmap, so the planet-center end is at the outside of the rings, and the outside-ring end is in the middle of the planet. See, the outer green ring is into the planet. The black "empty space" part is out at the edge of the ring system.



3. Render it from the top. Cut a slice from the middle to the edge. Now we have a "reverse-distorted" ringsystem bitmap.





4. Replace the original ring color bitmap with the corrected (reverse-distorted) bitmap. (Undo the 180 rotation in your W dimension if you have to). Voila! The rings are the proper width, now!

[töff]

PRODUCTION SCHEDULE rev. 2009-04-12

Sep-Oct Wayfarer #32 √ Chap.27 1. Titan
Nov-Dec Wayfarer #33 √ Chap.28 2. Rings of Saturn
Jan-Feb Wayfarer #34 √ Chap.29 3. Io
.................... √ Chap.30 .. Klish
Mar-Apr Wayfarer #35 X Chap.31 4. Ceres (Midnight City) - almost done
May-Jun Wayfarer #36 - Chap.32 .. Ceres (The Cereal Reverence)
Jul-Aug Wayfarer #37 - Chap.33 5. Mars - incl. Solar System Map!