I misunderstood your question. So basically, you already have the mousedragging — but you want acceleration depending on the the mouse position relative to the sphere?

How about this:

• Register where the user initially clicks on screen. You can do that using the mousePressed(MouseEvent e) method.
• Find the center of the screen
• Multiply the rotation by the distance from the initial mousePressed coordinate to the center-of-screen coordinate.

Example: rotationX = (dragDelta.X * (centerDelta(mouseOrigin.X, Center.X)))

Where dragDelta is the distance the user dragged. Center is the center of screen and mouseOrigin is where the user initially pressed at the start of the drag. The centerDelta method would return a sensible variable based on the distance from mouseOrigin.X to Center.X. So the further away from the center the user clicks, the rotation gains more force.

If I'm still misunderstanding you, and the actual question is how you get an acceleration effect — where the rotation slowly decelerates over time — then the answer would be the above and additionally decreasing the value of delta from center multiplier over time.

This'd work okay if the sphere is close to you, but might not work so well if the sphere is small on screen. Does this help? Or am I still misunderstanding your question?

EDIT: This, of course, does not depend on the user actually grabbing the sphere. If that's an issue then you could use Interact2D to check if the user is actually clicking on the sphere or not, and then calculating the distance from that point to the center of the sphere (instead of calculating the distance from the click and to the center of the screen).

The license for that demo is: Do what you like with it. Modify it, rip it apart, sell it, print it and use it as a wallpaper...

Excellent. Thanks for the source, and the quick response.

Just posted some information plus the most recent screenshots over at my blog, Think Artificial. If anyone's interested in keeping taps on what I'm doing.

• When Pet Projects Demand Attention: Sneak Preview of My Untitled Game, on ThinkArtificial.org (Oct 24th)

EDIT: Might as well post the screens here too. I'm making all models and textures from scratch.

Thanks Helge.
It looks like you're right on the texturing issue, shrinking the polygons worked! But I tried enabling flat shading on a part and it disappeared/became see-through, haven't figured out why yet. A play on the texture orientation helps make the archway edges look more sharp though, so that's cool for now.

Thanks for the compliments and advice, Remo. I'll definitely have a look at the DevKit.
I'm currently reading up on proper texture creation and application as well as finetuning my modeling skills (no real experience with it). If anyone's looking for a wholesome info on texture creation, I recommend 3D Game Textures: Create Professional Game Art Using Photoshop by Luke Ahearn. It technically contains tutorials that you could easily find online, but he presents it pretty nice and coherently.

That's great, and probably a lot simpler than trying to find an editor. From what I've seen it basically works the same way as when loading .3DS files, right? .OBJ contains a reference to the texture name, and you use the TextureManager to import textures with the same names as the ones contained in the .OBJ file?

I'll give it a shot. Thanks for a quick reply.