Retriving 3D infomation from a 2D point on the screen

[subbu]

Hello,

I am new to Vizard tool. I am trying to extract 3D information of the object, given a point on image which is rendered on to screen. I am able to get position and depth info. But how to
(1) extract structure and texture information of the object's surface.
(2) get the order of objects in ray tracing?

Any help, would be greatly appreciated.
Thanks,
Subbu