Just for kicks, I am making a 3D model of the Earth. I have a few questions...
Ok now--where can I find good textures for 3D planet models?
Celestia Motherlode may be a good place to check.
Using various descriptions of the size and dimensions of the Earth, I wanted to create a full-scale 3D model (no real surface detail). Now, I know of some of the limitations of creating a smooth sphere that is approximately 12800km wide, but what of getting some good textures of it?
Save yourself some problems and make it significantly smaller. I briefly tried experimenting with real-sized planets when I was putting them together for Cardinal Spear, and they had some rendering issues. The polygons were flickering in and out of sight and so forth, and trying to place the planets around in FRED was like hell so I ended up typing numbers in notepad.
Incidentally, there is an Earth model (amongst others) in re-released Cardinal Spear, so you might want to take a look at that as well... it has a texture taken from Celesti Motherlode with some small edits, a shinemap and a glowmap for night time city lights.
How hard would putting a texture onto a sphere be? What is the maximum texture size on the current engine (is it 2048x2048 like I seem to remember)?
Well aside from TrueSpace's hideous user interface it wasn't actually difficult, as soon as I figured it out and found the correct panels and settings... More difficult was to get PCS to convert the COB to POF without complaining about huge amount of normals.
Maximum "safe" texture size for the engine is 2048x2048 (if I recall correctly) but AFAIK it also depends on the graphics card. I can pretty safely use 4096x4096 textures at least for planets and/or skyboxes, never had any problems with them... At any rate, don't use square texture for a sphere if you can avoid it. It doesn't look good - a better solution is to use a 2:1 ratio like, for example, 2048x1024. Or if you have no problem using textures up to 4096 res, you can use 4096x2048 resolution textures.
Finally, could you really place an object over 6500km away? Is it possible to have invisible "layers" around the planet to separate the various parts of the atmosphere?
As I said, extreme distances tend to generate problems with rendering, at least according to my limited experience. You *can* do it but what it looks like is a different thing altogether.
What comes to atmosphere layers... yes, it's possible, but the advantages wouldn't likely be worth it. Essentially you would need to meddle with alpha transparency for the texture.
Also you would need to make the outermost "shell" the actualy body of the object, then the inner ones would be subobjects and the actual surface would be the last subobject on the list, so it would be rendered last... And it doesn't even look very realistic or good - you would need dozens of shells to make the atmosphere look even remotely realistic. I tried it with one shell and ditched it. I can find a screenie if you want to judge by yourself, though.
