Do you mean to "pick" a object3d?
if so ,search mouse pick in forum for more details
set the collision mode in your object3d and then
SimpleVector simpleVector = Interact2D.reproject2D3DWS(
camera, frameBuffer, touchX, touchY).normalize();
Object[] ii = world.calcMinDistanceAndObject3D(camera
.getPosition(), simpleVector, 10000);
in ii[1] that's the object3d which be touched or null if nothing is been touched.
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Sorry i didnot get your question after a review