Motile islands...A Question

Dollan · Post #1by **Dollan** » 30.08.2004, 00:32

I'm looking a little ahead of where I am right now, but I thought I'd pose the question, if only to give me time to think on it.....

One of the upcoming systems for my ArcBuilders celestia add-ons is the planet Orra (actually a moon orbiting a Jovian) in orbit of Beta Hydri. Orra is a water world; in brief, it is a melted version of Europa. In the setting, one of the only remaining major forms of life are great motile islands of algae-like material. Over thousands of years they form great islands several square kilometers in area, and up to 700 meters thick. Many of the truly ancient islands are visible from space as islands. however, they do move, and so their positions are not geographically fixed.

My question is, how could I display this in Celestia? I have a generic water world map already. But I'd like to show a smattering of these islands, and I'd like them to move over time. Any thoughts?

...John...

Post #2by **granthutchison** » 30.08.2004, 01:00

Define them as models (or paint them on one of Selden's maps), and place them in circular orbits with radii equal to the planet radius, but with a variety of inclinations, nodes and periods. They'll all move in great circles, admittedly, but to a casual observer all that'll be evident is that the constellation of islands shifts over time.
Hmmm ... is there still a problem with models being superimposed on top of the clouds?

Grant

Rassilon · Post #3by **Rassilon** » 30.08.2004, 12:59

Actually he could model the main part of the planet as the sea. The second model as the land and the third as the clouds. If your familiar with displacement maps you will know to make a height map from your land masses where the ocean is black and the land is white. The ocean could be a simple sphere with color added and speculars. If you do not care about surfaces do not worry about double siding the clouds. If you do however you will notice that the clouds appear black underneath and with ambient light on none you will not see them anyway on the surface. Unless you make them emissive.

If you define an ssc file with 4 seperate definitions:

Main
Land
Clouds
Atmosphere

You can achieve this...

Make sure the orbital elements of all 4 are precisely the same!

Dollan · Post #4by **Dollan** » 30.08.2004, 15:31

Whew... this is gonna take me a while to get. I've really only just started add-on construction with Celestia, and have NO model-making experience (I don't think I even have the tools for it). It might take a while, but it could be a fun experience!

...John...

rthorvald · Post #5by **rthorvald** » 30.08.2004, 16:20

Dollan wrote:just started add-on construction with Celestia, and have NO model-making experience (I don't think I even have the tools for it)

Rassilion?s suggestions does not require any 3D models; just a cloudmap, normalmap, spc map and surface map. If i understood him correctly, he suggested you painted the algae islands on the cloudmap (without any clouds, of course). If you make this as a single png file, you can set it to move as slow as you want. But all the islands would move in sync.

Grant?s idea require you to use 3DS models, but you don?t need to make them yourself; find a free asteroid model with the shape you like, and give it a fitting texture in the SSC definition.

If you want to customize the model, get Anim8or. It?s free, and has a relatively easy learning curve compared to other 3D software.

Here?s one more idea: instead of using 3DS models, just define the islands as moons, and give them an oblateness (in the SSC) of 0.9. They will show up as discs (more or less), floating on the water. This has the advantage that you can combine nightmaps, cloudmaps, atmospheres and ground maps on them to get whatever surface effect you want, and each of them can have different speeds and paths.

-rthorvald

eburacum45 · Post #6by **eburacum45** » 30.08.2004, 16:33

I am interested in this topic too; my waterworld, Panthalassa, could also benefit from some increased detail...
if the algae islands were made into moons then they would appear above the clouds, I think- what would be nice would be concentric layers of transparency...

Rassilon · Post #7by **Rassilon** » 30.08.2004, 17:57

Actually my sugesstions required a modeling program. Dollan send me the textures and Ill send you the planet if you like...Its not as easy as I stated for those not experienced a bit in modeling...Check your pm's

rthorvald · Post #8by **rthorvald** » 30.08.2004, 19:01

eburacum45 wrote:if the algae islands were made into moons then they would appear above the clouds, I think.

No, you can define how high up the clouds go, and the moons can orbit as close to the ground you want (even below the surface). So, just give the moon an extreme oblatenes, and have it orbit exactly at ground level. The only thing to remember is that it has to be fairly big because Celestia clips objects a little off, so you get viewing problems if you are very close to small objects embedded in larger ones.

eburacum45 wrote:what would be nice would be concentric layers of transparency...

If depht sorting has been fixed in 1.3.2, i think you can have that (i wouldn?t know, as OSX still is at 1.3.1). The method would involve having two planets orbiting the one inside the other, with the cloud map of the inner one appear above the surface of the outer one...

- rthorvald