How to select the vertices that had been rendered.

[Dave]

Hi,

I am currently working on region selection, but in order to do so, I
need to know what are the vertices or polygons that was rendered on
the screen. I don't want to include the polygons that was hidden at
the back, is there any function in O3D or WebGL that can detect what
polygon had been used to draw the mesh, and what had been culled.

I tried the back face culling, but does not work well.

Regards,
Dave