how to draw a 2D line with color in 3D world?

[qjvictor]

I need a 2D line to split the 3D world, and the 2D line should be in red or green, how could I do this?
and what's the pixel position of 2D line?

Thanks.

[EgonOlsen]

Using the software or the hardware renderer? A horizontal, vertical or arbitrary line?

[qjvictor]

The line's position will be changed according to the position of a 3D object in the screen. It depends on the camera's angle.
Is there any method to change the 3D position to 2D position in screen?

[EgonOlsen]

You can use Interact2D.project3D2D()...this thread covers a similar topic: http://www.jpct.net/forum/viewtopic.php?t=663
However, when using the hardware renderer, you've to use the OpenGL-binding directly to draw the line. When using the software renderer, you can use Java2D for that.