Obtain absolute coordinate of a 3D object?

[jiapei100]

Hi, all :

I proposed the question at http://www.java-gaming.org/topics/obtain-2d-onscreen-projection-coordinate/21715/view.html

In fact, my current case is like:

I've got two balls, a bigger one and a small one. The small one is attached to the bigger one at somewhere on the surface.

The bigger ball is rotating, so the small ball on its surface will move (translate).

Thus, my java3D group structure is like :

1   2   3

--TransformGroup of Big Ball(Big Ball) --------BranchGroup ------------------TransformGroup of Small Ball (Small Ball)

When the big ball rotate, surely, the small ball attached on the surface of the big ball will move,
I mean, there exists on-screen translation.

I would like to know the absolute 3D coordinates of the small ball after the big ball transforms.
And, I would like to know the 2D on screen coordinates of the small ball.
For example, if the on screen canvas is of size 640*480,
I would like to know just in this current frame of image,
where about is the small ball within this 640*480 image? (100, 150) ? Or somewhere else???


Seriously urgent and needs your help.


Best Regards
JIA

[jiapei100]

Problem solved.

Refer to http://www.java-gaming.org/topics/obtain-2d-onscreen-projection-coordinate/21715/view.html

Rgds
JIA